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First let me talk about the image above. This is the plan view image for what would be a square log home. It shows in brown square logs of rail road cross tie dimensions. We would use 7″x9″x10′ where the 9″ dimension is horizontal giving 9″ thick walls. I show where logs overlap on the ends in in lap joints on the sides. These joints can be constructed in numerous ways. Logs every other row will be offset 5′ or half the length of the logs so that joints are staggered. This means that on corners every other row will use a 5′ log. Also using a particular type of adz fake chinking groves can be cut out between the logs. Then by tacking in some metal lath or chicken wire and plastering fake chinking can be achieved. Chinking was originally used in American style log structures to fill in gaps between logs where logs were not tightly fitted. They either did this for economy of wood use or because of lack of skill needed to fit the logs tightly as they did in Europe.
This next set of images is of the above design. This is a concept drawing.
No or incomplete engineering has been done.
I don’t show door or window locations. Also inner walls could be added to divide the spaces into rooms and hallways. You can also imagine where porches might be, in fact they could be all the way around. Below lower floor level will be a rock or block stem wall up at least 1.5 feet if not higher. The stem wall could be wide so that the floor joist rest on it as well as the log walls.
The nice thing about the Dog Trot design is that it can be constructed one module at a time as the owner and usually owner builder has time, money, materials and manpower. You may also live in the completed sections while you expand and add on. Even the 2nd story could be built later, though the roof structure would have to be removed and then added on top.
One module from stem wall up 8′ high would require 168 cross ties, that is 12 every 7″ of height. If you could get these at $25 each, a bare min price under today’s economy, we would be talking about $4200 per each lower module. If you could make these yourself with a mill cost might drop to $4 per cross tie or $672 per lower module. Could possibly get that cost down even more. If you milled this yourself from a trees you might need trees that are 12″ to 14″ in diameter. You might get 3 logs per tree. If it works out this way you would need 50 to 60 trees for on module. And remember in trying to get logs of this exact dimension you will also end up with some lumber to use. So you can see the possibilities of this design for yourself.
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As a prerequisite you may want to read my Timber Frame, Post and Beam, Beam and Stringer article.
Log cabins come in a few types.
- Type of Logs
- Round Logs
- Square Logs
- Whole Logs
- Half Logs
- Partially Round Logs
- Orientation of Logs
- Horizontal Log Walls
- Vertical Log Walls
- Single Log Walls
- Double Log Walls
- Fit (how tightly they go together)
- Well Fitted
I have a lot to write here, so keep check on this article over time. I decided to go ahead and publish this article in a somewhat incomplete state. I have more written about logging currently than anything else. But at least it will give you some ideas.
Log cabin building is a fairly huge topic and I have no intention of being comprehensive here. I also have no intention of competing with the many great books available on this topic. I will simply note some interesting things that I have learned in my studies and from conversations thus far.I will not be covering foundation, stem wall or chimney of rock, concrete or masonry in this article. I may talk about chimneys made from small logs spaced apart well and infilled with mud or cob. The log cabin books and other books cover these subjects well. I will write about these topics in other post later.
Log walls are strong, meaning they can bear a lot of weight for roof structures. They can bear something around 100,000 lbs per linear foot, depending on width and type of wood. This means that little engineering is needed for log structures. If you keep things simple no engineering would be needed for the roof structure. Log walls are energy efficient and can have R values from 20R to 35R or even higher if it were a double wall. Soft woods tend to have higher R value than Hard woods. As an example your typical 2×4 wall is R11 and 2×6 wall is R17.
I talk about what I have read and heard in regards to logging in this article. It has been recommended that if you do not do logging as a profession then you most likely will want to hire this done. Logging is dangerous work. Machinery is dangerous to operate. One idea I was given for getting logs is to buy a wooded lot and go halves with a logger to log them for you. Keep the lot for an investment and campsite or a place to keep some goats. In the USA in many areas large logs are difficult to come by. Most areas have nearly all pulp wood for timber, especially in the south east. And in fact wood is being grown now for the growing array of composite construction materials. This means for glue-lam beams and post, oriented strand board and particle board. So logs may have to be imported from out of state for many log homes. Many are imported from western USA. Logs need to be seasoned before construction for a year or more. This is where they dry and shrink.
Of the types of logs I personally like square hewn logs the best. For one thing much of the sap wood that would rot is sawn or cut off in order to make the log square. I like the looks of the chinking so I’d probably cut a chinking groove between two logs fitted tightly and make up fake chinking. After boards have been removed from the outside of larger logs often the heart wood is left which if left at the dimension of 7×9 make great cross ties. At the time of this writing a 10 foot 7×9 hard oak cross tie might cost $25 to $40. It would require about 240 of these to make a 20’x50′ or 900 ft2, single story cabin. So at $25 each we are talking about $6000 for the cross ties, and that doesn’t include delivery charges.
- Round (Lincoln log style)
- Square end
- Diamond end
- Doves tail end
Logging and Milling operations.
First let me say that logging is very very dangerous. One must learn to correctly determine direction of the tree fall, and even then there is a chance that it may veer off course from planned direction of fall. Wind, splitting and rot, leaning or off balance, improper final cut and lodging in nearby trees can all change the direction of fall. A tree can split and kick backwards towards the feller. And let us not forget about the falling limbs called “widow makers”. A tree that one tree falls against can snap back and throw a limb like a sling shot towards men and equipment. Below I will list some safety equipment that should be worn.
- Hard hat
- Goggles or face shield.
- Leather gloves
- Leather Chaps
- Steel toed leather boots.
Logging equipment can be very dangerous be it tractor or skider, truck trailer, chainsaws, axes, hand saws. Saws and axes should be placed in the open laying flat on the ground and not leaned against trees and equipment. Chain saws should be placed on and against a sturdy surface when started, not simply held in the air. Chain saw should be off when checking or adjusting chain tension. Beware of hot mufflers and parts that could cause burns. Logging chains can break and fly towards people and equipment at high speeds with great force. Respect equipment and ease into learning the use of them. Learn to gauge your comfort level and don’t hurry. Learn to get a feel for the handling and operation as you would in most other kinds of work. Don’t be overconfident or careless.
Notching and Back Cut and Felling
A notch should be cut in the side of the tree at the desired direction of fall. This notch is horizontal at the bottom and about 1/4 to 1/3 the diameter of the tree in depth. Then at a 45 degree angle from back of notch upward to outside of tree bark. Large trees may need one small notch first then larger notch made from the first small one. Or on very large trees two small notches, one on top of the other, then the large one from those two further in. With an axe on larger trees it may be necessary to chop on one side then the opposite then middle to get chips to fall off then rinse repeat. It is possible for two fellers to chop at the same notch at the same time to speed up the notching. If your saw bar is not long enough to go all the way through the tree, then cut one side first on the back cut until the remaining uncut section is shorter than your bar length. For leaning tree’s that are leaning in the direction of fall, cutting on both sides of back cut first will lesson splitting and kickback.
The back cut should be horizontal and made about two inches above the base of the notch and towards the notch and direction of fall. You can place the double bit axe in the notch and use its handle as a pointer to give you the direction of fall. The back cut should be made to withing a couple of inches of the notch and should be above and over the back of the notch by an inch or two. The wood left in-between the notch and back cut forms a hinge during the fall of the tree. As the tree begins to fall yell the famous word “Timber!”. This is a warning to others in the area to watch the tree as it falls and be ready to move fast if needed. The back cut hinge can be left thicker or thinner on one side or the other to guide the direction of fall at the last moments. If two people are using a cross cut saw to make the back cut one should keep the other informed about how close he is to the notch.
Other difficulties might be pinching of saw on the back cut in which case you would use a sledge and wedges to pry the tree off the saw. Wedges may also be needed for leaning or off balance trees. If splitting is anticipated wrap the tree with a log chain and use wedges to tighten the chain around the tree. The final portion of the back cut may have to be timed with the wind. If the wind is in the direction of the fall then wind can be used to push the tree on over. If its against the direction of fall then try to finish the cut as the wind slows or dies down. If the wind is to one side or the other then it can push the tree out of the direction of fall a bit. Time the back cut and the thickness of the hinge on each side appropriately. If the wind is too erratic or strong felling operations might not be advisable at all.
Trees should not be felled down slope, only up hill, or up hill to one side or the other a bit. Trees that are felled down slope tend to break or shatter. The feller should move slightly uphill and to one side or the other as the tree falls. A tree may kick backwards down hill and strike the feller who is down slope from it. Try not to fell a tree on rocks or across other felled trees which would cause shattering and splitting. If a tree lodges in another tree then use a tractor and chain to pull it off the stump at the base. Never cut the tree that it is lodged in and don’t try to stand on it and shake it to get it to fall. A stump should be no more than one foot higher than the ground on the uphill side. Sometimes because of rocks this is impossible though.
Standing on the tree trunk cut limbs off is tricky dangerous business. Inexperienced limbers should avoid this until they are confident after seeing the reaction of trees as limbs have been removed. Trees tend to roll a bit during limbing. Sometimes on large limbs notches may need to be cut out similar to the notching for felling except that its more of a 90 degree notch. Then a saw may be used to finish the cut horizontally.
This is where you cut sections (logs) of the tree out for lumber making. The person who decides where the tree is to be cut should probably have some milling experience and also know about how rot and other defects affect milling operations. A tree should be bucked such to get the most use from the logs/boards (board feet). There are many defects which can affect bucking and calculating board feet. A few would be rot, punky sapwood, splits, fire damage, large limbs, knots, bends, forks etc.
Calculating Board Feet
Board feet can be calculated with what is called the Scribner C Log Rule. This table is imprinted on a ruler that is carried by the person who calculates board feet. It has diameter across the top (6″ increments) and length down the side of the table (1 foot increments). Table values are in (tens ‘meaning times 10’) of board feet. There are quit a few guidelines for how one deducts for various defects from the total board footage of a perfect cylinder. Tree’s that vary much in thickness may need more than one board footage calculation for a single log.
Beware that trees can have gravel, rocks and metal as in spikes and nails and staples in them. Metal and saw teeth can become shrapnel. Also note that there are some people around who resharpen band saw blades.
Chain saws and associated equipment.
I hear that the two main best brands for chain saws are Husquvarna and Stihl. Stihl has been recommended to have the best performance however parts are harder to come by than for Husquvarna.
- Gasoline powered Chain saw (saw, bar and chain)
- Chain saw oil to be mixed with gasoline.
- Chain saw bar oil.
- Chain saw grease gun (for greasing the bar sprocket)
- Rip Chain
- Wrench for taking chain saw brake apart to get chain off.
- Screw driver(small philips) for adjusting chain tension and idle speed
- Sharpening File (round file) and Handle
- Angle guide for hand file
- Electric Dremel tool or drill motor with sharpening stone and angle guide.
- Air powered sharpening tool for trucks with air systems.
- (Air powered chain saws have been used in the past)
- Air hose for air powered chain saw.
Other felling equipment.
- Double bit axe
- Broad axe.
- Heavy axe.
- Logging Chains.
- Cross cut saw (one and two man)
- Bow saw (for limbing)
Logging operation tools and equipment.
- Near 25 horse power tractor.
- Team of mules, horses, donkeys or oxen.
- Truck or Van that can pull 3 to 4 tons.
- Twin axle flat bed trailer that can haul the tractor or a few logs or lumber.
- Log arch for moving single logs.
- Power winches.
- Logging Chains of various sizes.
- Wedges of varying sizes.
- Sledge hammers of varying sizes.
- Boards to use as ramps for pulling logs onto trailer from side.
- Log dogs (A rod with spikes on each end)
- Circular saw mill powered by pickup truck rear drive wheel, truck set up on blocks.
- Small Band saw mill.
- Granberg Chain saw mill attachment (Alaskan Small Log Mill).
- Beam Machine chain saw guide.
- Electric Plainer
- Table Saw
- Two man rip saw (for saw pit).
- Hand Plains
Wood Roofing Equipment and materials
- Mallot and Froe (for splitting shakes ‘wooden shingles’)
- Riving Horse
- Shaving horse
- Draw knife
- Weight Poles and struts (for weighting wood shakes down until they dry)
Standing seam metal roofing equipment
Beam working equipment
- Draw Knife
- Boring Machine
List of corner notch types
- Half Dovetail
- Compound angle Dovetail
- Full Dovetail
- Keyed Dovetail
- Half Notch
- Diamond Notch
- Square Notch
This next set of photo’s shows the operation of the Grandberg Alaskan Saw mill. I am using my Husquvarna 55 with 18″ bar. It took about 30 minutes to saw off that first side. I was resting me and the saw a lot. It really moves along a lot faster than that. I bought two 10 foot 2×4’s for the straight edge. Using some scrap I tied the 2×4’s together on bottom and nailed the scrap to the log, with the 2×4’s on top of the scrap. One thing to remember is that you don’t want your chain saw hitting the nails, so make sure its moving along deeper into the log than the nails penetrate.
If you do not get the first side perfectly flat for some reason you may place on top of it a couple of strips of angle iron nailed down to be a straight edge. As a matter of fact it would be good to make an angle iron guide or square tube steel guide similar to the 2×4 version I have below.
I realized after I started that I had to move the 2×4’s out so that they overhung the log to get started. In reality I should have bought 2×12’s to mill 10′ logs. It should hang over a foot or so on each end. I intended to cut 10′ boards from this old dried elm stump. However 9 feet or so is all the practical length I can get from this log. Next I intend to cut of at least one side or maybe both with a tool called the Beam Machine and my chain saw. Then I will cut 2″ to 3″ planks from this log to use as garden box boards.
I demonstrate the use of the Beam Machine which uses a single 2×4 as a guide to cut off the side of a log. I realized after I started that I should have been 1″ further in. It looks to me like lumber could be made using this Beam Machine. If you didn’t want to use the lumber made this way for your home then it could always be used for barns, chicken coops and dog houses. The beam machine needs a flat surface made with the Alaskan Saw mill on larger logs or on 6″ to 8″ dia logs you would simply nail the 2×4 down the top of the log. You could then saw off each side without moving the 2×4. Rotate 90 degrees and do it again and you would have a beam of 5″ to 7″ in size. On a larger log you might first use the Alaskan saw mill to flatten to sides then use the beam machine to cut multiple beams from one log.
|The Classic Hewn Log Home2005Charles McRavenStory Publishing|
|Old ways of working wood|
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What is a yurt? Is it a tent? Is it a hut? Is it a shack? Is it a cabin? Pick up the book titled, “Build a Yurt!” This book was written by a guy in the 1970’s that actually visited Mongolia. This web site has a nice gallery of yurt photo’s. Yurt Gallery Yurts are actually called a Ger in Mongolian. Ger means home or dwelling. It is a light wooden frame, circular like the native American Tee Pee, yet shaped more like a short grain silo. I think we have all seen grain silo’s in America. It was probably covered in hides by the Mongolian’s. They may have used some heavy cloths (canvas) as well. It was insulated with thick felt made from animal hair. They were tied down with stakes and guy ropes or chords, in the similar fashion as tents. Yurts have a sky light at the top which serves a similar purpose as the hole in the top of the Tee Pee.
You may want to read a related article Green? my blog post on the green building trend and green living.
Yurts were known to withstand hurricane strength or blizzard winds of around 90mph(144kph). They are as strong as most of our buildings when it comes to wind resistance. Since yurts are round houses they are very energy efficient to heat. Yurts consist of a frame of 1 inch(2.5 cm) by 2 inch(5 cm) or 1 inch(2.5 cm) by 3 inch(7.5 cm) sticks or ribs. These are oriented in a lattice work pattern for both the side and the roof support. Of course these can be built right on the ground or on any kind of floor and foundation. I list here a parts list for a yurt which will be 22 feet(6.7 m) in diameter and have about 7 foot(2.13 m) side walls. It will rise to about 12 (3.6) to 14 (4.2) feet (m) in the middle. This yurt will be constructed on a wooden floor which will be about 2 feet(60 cm) above grade (ground level). It will have one door and the sky light and possibly some windows. When completed it will have 400 square feet(37 m2) of dry floor space.
11.33 foot (3.45 m) radius. 22.66 foot (6.9 m) diameter. 403.2 square(37.43 m2) foot floor space. 71.18 foot (21.69 m) circumference. Here is a Yurt Math PDF The side walls will be built with sections of lattice. The lattice is made from 1×2’s and will be about 8 feet long. The roof lattice will be made from 1×2’s(2.5x5cm) and 1×3’s(2.5×7.5cm) The 2(5cm) inch side will be on top and laid horizontally. The 3 inch(7.5cm) side will be vertical and function similarly as rafters.
- 140-1″x2″x8′ (2.5cm x 5cm x 2.43m) sticks for wall lattice.
- 70-1″x2″x12′ (2.5cm x 5cm x 3.65m) sticks for roof lattice.
- 70-1″x3″x12′ (2.5cm x 7.5cm x 3.65m) sticks for roof lattice.
- 3/8″ (9.5mm) steel cable 75 feet(22.86m) long (for the 70 foot (21.33m) perimeter)
- Rope for guying. Or cable for guying.
- 6 to 8 Wooden or Rebar Steaks
- Turn buckles for tightening the steel cable.
- 6 to 8 Cable clamps.
- Small finishing nails.
- 4’x4′ (1m x 1m) foot piece of Plexiglas (for the sky light).
- Side covering. 8 feet by 72 feet in size. (2.43m x 21.94m)(canvas or vertical wood or tin) Contact an awning maker for this.
- Roof covering. This is a cone shaped piece. in 11 feet the roof will rise about 5 feet(1.52m). (canvas or wood shakes or tin) A circular piece of about 25 feet(7.62m) in diameter might work. The circumference would need to be 71 to 80 feet(21m to 24m) maybe.
- 500 feet (150m) of Nylon chord for tying down the roof covering, if the roof covering is made of some cloth like material.
- Linseed oil, to be rubbed onto the lattice pieces.
Parts list for the floor.
- 6, 6″x6″x11.33 feet in length beams size (can be larger than 6×6 such as 6×9). The angle between the outer hexagon beams is 120 degrees. The angle between the main beam across the middle and the diagonal is 60 degrees.
- 1, 22.66 foot 6×6 (6×9) beam.
- 44- 2″x6″x10′ for floor joist spaced every 1 foot
- Or 22- 2″x8″x10′ for floor joist spaced every 2 feet (if used 6×9 beams)
- Joist hangers, metal sheeting for custom hangers, or pipe strapping. If using strapping then toe nailing is required. Do not end nail for support.
- 1x planks for flooring. If 1×4 will need 132. If 1×6 will need 88. They will be 10 foot long. Planing and tong and grove jointing would be nice.
- Plywood for cantilever floor support. This is for the edge that hang over the beams. Figure a 71 foot circle then draw a line from one edge of the circle to another edge which is 11.33 feet long. There will be 6 such areas.
- 100’s of 16 penny nails or long wood screws.
- Stone or blocking for support to lift the floor 1.5 feet off the ground.
- Linseed oil for some rot protection (to be sprayed on beams)
An insulated floor might need these parts..
- 6 mil plastic to be draped over the joist.
- Fiberglass Batt insulation.
- Or wheat straw as insulation. (if I used this I think I’d want a light weight plywood underlay.
- Staples and Staple gun.
Fly Screen might be needed on top and sides to keep insects out.
Instead of the yurt lattice for side, consider a normal 2×4 stick frame side. For the top use two layers of 1″ plywood pieces cut in circular fashion to make a wall plate or 2×4 pieces with angles cut to fit perfectly between studs. A metal top plat would work well also. Use metal plates and sheeting for extra support.
A tin roof with standing seams would be easy enough to make. Would need pieces of tin that were about half a foot wide at the top and maybe 2 or 3 foot wide at the bottom. Top to Bottom edges would be bent up at about 2 inches. You would lay these side by side then use some tool to bend the seam of the edges of two pieces over once then twice. These pieces would be nailed at the top. Something at the top would cover the nail holes, such as the plexiglass sky light cover.
Cost of a yurt?
I shopped around in our area a bit and realized the yurt frame was going to be fairly affordable. Just the frame and all the parts needed to get the frame up might be less than $500. If you look at my article on Log Cabins you will find near the bottom photo’s of my milling operations using the Alaskan Small Log Mill, my chain saw and the Beam Machine. I calculated from that one log I could make 128 10’x1″x2″ pieces. I would probably need a table saw or skill saw to make the 1×2 pieces from 2×18 planks. And at a cost of only about $10 in fuel and oil.
I’m not sure what an awning maker might charge to make the top section and side section but material is near $4 per yard. On this first yurt we will be cutting pieces from an old revival tent. This is some kind of rubberized canvas. A person could use the clickable calculator below to calculate the size of wedge shaped pieces of material needed for a roof piece. You would enter the slope distance and not the horizontal distance for the radius in this case along with the number of pieces. To figure the shape of the round edge simply use a string nailed at the apex, then with a pen tied to the end of the string mark the arc shape for both the outside and the sky light hole. Each piece could then be cut out and sewn/glued together. This could also be used to calculate the sizes for tin roof pieces.
The wood for the floor is a different story all together. I priced this at $2500. It could be done cheaper if rough cut by some local mill, maybe $1000 or so. I bought some tools to mill my own lumber. A used chainsaw, $250. Beam Machine chain saw attachment $50. Grandberg mill chainsaw attachment $200. We plan to mill all the wood for the yurt. Not counting the cost of the milling equipment we hope to have less than $500 into this yurt when finished.
Yurt kits go for $5000 to $8000 or more. If you have the money, the kits are probably worth every penny, though I’m sure a bit overpriced.
I am wondering why the industries of the world do not mass produce yurts and offer them at rock bottom or at cost prices for the homeless around the globe. Or at least to missionaries, peace corps and for disaster relief. The yurt is the perfect temporary shelter for any location anywhere, they just need to be shipped. Its darned arrogant to think that because other peoples around the world can’t afford a modern home that they should have to live in card board boxes or homes made of scrounged parts or whatever. The existence of living in a yurt would be rich to many homeless peoples around the world. Churches around the globe should make these for their missionaries with donated materials. Churches should be the leader in getting this type of housing to people in 3rd world countries.
How about putting yurt on stilts in a flood prone area. It is light weight and this would be easy to do. What about putting a yurt over water? Sure, on stilts over water, would make an awesome lake cabin for lakes with well known maximum water levels.
A ladder could be added which goes from floor up to the sky light for added support, as well as providing a view from the peak of the yurt. Maybe even a great shooting position aye?
A 2nd floor could be added which would serve as a loft. In the above design which I lay out in this article consider an inner 12′ diameter floor where the joist of this floor is 6 feet 6 inches off the main floor. This should give 5 to 6 to 7 feet of head room. 2 to 4 people could then sleep in the loft area. A ladder would be needed for loft access. It would need to be supported by some sturdy columns. These columns may need to descend through the floor to concrete piers and footers. Bracing may also be required on the columns.
Could a yurt be made from poles for the lattice works? I’m sure Mongolians used poles. I’d guess 1 to 3 inches in diameter tree’s and limbs could work if they are straight enough and don’t taper too much.
How about a bamboo yurt? Would river cane or fishing pole cane work for a very very small yurt? Or how about combining small river cane into chords which make up the yurt poles or sticks for the lattice.
Other variations on the yurt theme. For example if its a permanent yurt, many different things would work well for round, cylinder walls. Then the yurt wood top could be used as traditionally.
Earthen walls to include. Super Adobe, Adobe, Rammed Earth, Earth Bag, Earth Tube.
How about papercrete sprayed on the yurt frame? I’m not sure that I’d do the roof section that way, but for the wall lattice this method would work nicely, and provide some insulation. Papercrete has an R rating of 2R or 3R per inch of thickness. If you couldn’t stand to cover the nice wood lattice with papercrete then blocks could be made and stacked around the outside of the lattice as the wall covering. The roof covering could then drape down over the papercrete wall veneer. I sheet and some vapor barrier plastic could be between the lattice and the papercrete wall veneer. Other variations of wall veneering might be possible too, such as the earthen methods I listed above.
Verticle Log walls can be done using a variety of methods.
Grain Silo walls.
Steel or metal frame instead of wood? Any kind of scrap metal might work for this. Tac weld the frame where the lattice pieces cross. Would make a frame way stronger than the wood yurt frame. Use angle iron for the roof for at least one direction in the lattice. Flat iron could be used for the sides. How about rebar? How about Metal pipe? PVC or Plastic Pipe filled with grout or some other material to make it rigid? And as long as we are putting up metal frames, how about gunite or shotcrete? Plaster? of course metal lathe or chicken wire might be needed. The yurt frame and structure and design could be made many different ways if one put his mind to it.
I was told at a Genghis Khan exhibit, where they had an authentic yurt on display, that it took 10 men 10 days and 200 sheep to make the cover for one yurt. If you are interested in felting yourself, look up felting machines on Ebay. Also one can hand felt with felting needles (not me). A felting machine resembles a sewing machine in appearance. Basically all animal hairs have joints. If you wet the hair and agitate it, the hairs align an interlock making felt. Wool, Angora, Mohair and other animal hairs can be felted. If the felt is thick enough its even water proof. It insulates really well.
The way the mongols made felt was to take a felt mat and add a layer of fresh hair to it, wet it, then roll it up like a rolled up carpet. Then they would tie it to a rope and drag it for miles behind horses. The new felt would then merge with the old felt.
Update on our yurt plans. We were first going to build Gary Tuck a friend of mine a yurt. We had decided it might go good next to a good sized pond on their place. The problem we were having was in keeping the cost down near $500 for the whole project. We have had found a way to do that but it required milling quit a few logs for the floor decking and structure. Not having time for that has postponed the whole project a year. However, Gary Tuck recently found a source for free 4’x8′ pallets. I also have a brother that can get me random sized pallets for free from his business. So we have new plan.
We can get used light poles from the power company for free. These are treated so they would make great post/piles. His pond’s water level usually drop 4 feet or so in summer. So we are now planning to construct using these post a platform/deck 1.5 feet off the ground at the lowest point and probably 3 feet off the water. It will extend maybe 4 feet over the water when the water is at normal full levels. We will put in the piles, then attach some 2×4 bracing to them. We will attach treated 4×4’s on top of the pile to run horizontally as the main structure for holding up the pallets. We will staple 6 mil plastic to the underside of the pallets. The pallets will lay on top of the 4×4’s and overhang a foot all the way around on the perimeter. The area under where the yurt will be placed will have used/recycled fiberglass batt insulation stuffed in that we will take from an abandoned mobile home. We will then nail down thin plywood sub floor on top of the pallets.
Using my chain saw I will cut the 2×4’s off some of the pallets to make 1.5’x1″x4″ flooring planks. We may floor the entire deck with this. Then sand it with a huge electric buffer/sander. Then water seal it. The area where the yurt will go however will need a 22’diameter additional flooring in a circle shape. We will mark this area and lay down some additional flooring and cut it to shape with a router. Again sand it and apply water seal. This will make a deck 28’x28′ leaving 6 feet on the water side for a porch/deck that overhangs the water 4′. There will be 3′ on each side of the yurt on the sides. And the yurt will be at the edge of the deck on the land side opposite the pond. The total cost in this may go slightly over $500 maybe even up to $750. We intend to mill the lattice framework from logs. And use an old revival tent to make sides for the yurt. The roof may still be a problem. I’m trying to talk Gary into roofing it with #10 cans used as shingles. Though I’d prefer a canvas roof if we can get that cheaply enough. If we can’t then the price will go up above $750 to who knows how much more, maybe $1500.
|Build a Yurt
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Of the books on the market for Timber Frame construction that I have seen only one slightly impressed me. “Timber Framing for the Rest of Us” by Rob Roy. As a matter of fact all of his books have impressed me so far. Most of the books on the market are picture books that tell you about Timber Frame homes. They are mostly to get you interested in having one built for you. Rob’s book goes into some good detail about the simpler frame construction and design. He also uses homes he has built as examples. He tells you how you can mill your own beams and other interesting details. He gives you some very basic information in regards to the engineering of beam size for floors or roofs. None of the books go into how you design or calculate the strengths in a frame.
Most homes in the USA are Stick Frame, meaning 2 inch by so many inches sized lumber in construction. Timber frame means structural frame made from beams or post that are larger than 5×5 inches in dimensions. You probably think of Amish or maybe Mormon made homes when you think of timber frame. Why are most homes not timber frame? Large trees are difficult to come by in many areas, therefore beams or logs must be imported. Not a lot of builders specialize in timber frame and are therefore not extremely skilled or efficient at this type of construction. Also if you do not have some nice blueprints or design specs for a frame you want to build, then you would have to possibly hire an Architect or a Structural Engineer to design the frame. And if you want old fashioned joinery with wooden pegs an Architect or Engineer may not even be able to help because they only have calculations which deal in metal bolts, pins and plates for connections. When constructed under code restrictions beams must be graded, so that means you must either buy them as pre-made, pre-graded beams or if you mill them then you must find someone to grade them.
In the past history of this kind of construction most frame designs and construction details and joinery were handed down generation to generation. Copied construction designs and use of the same species of wood generation to generation meant being assured that the structure was sound, as it had already past the test of time. Today if you are designing the frame from scratch then you are probably a structural engineer. You would have a text book to guide you in calculations which would determine the strength of any kind of design you choose. I’ll list some sources of information relating to this.
- National Design Specifications
- International Building Code
- Timber Construction Manual
- Uniform Building Code (Western USA)
- Standard Building Code (South Eastern USA)
- National Building Code (North Eastern USA)
- Design of Wood Structures (College Text Book)
- Lumber and Forestry Associations also have information.
- Lumber Producers have information.
Now did that just scare the living poo out of you? Yes wood is not a simple material to work with at all on the scale of timber frame, post and beam, beam and stringer. Its not even simple in furniture. You certainly want to make sure your design is safe for occupancy. Even engineers make mistakes right? When human lives are at stake the design details are all the more important. This is why architects and engineers are paid the big bucks. However I must say that after reading the text book, “Design of Wood Structures”, I have begun to really get the jest of what is going on when they calculate the strengths of a given design. Though I have not worked the problems myself. Merely reading that book has greatly broadened my overall understand and comprehension of the nature of wood and working with wood.
So how do they determine the strengths of a piece of wood? In a lab they gather 100 high quality identical samples 2x2x30 inches of a given species of wood for testing. They stress each piece with equipment which show the pounds of pressure or stress per square inch that is being applied. They stress each piece until failure. 100 recordings are made. The list is sorted least stress to greatest stress. The lowest 5 are thrown out, so that the wood is determined to fail a the 95th lowest value or greater. In formulas a safety factor of 1.25 is applied depending on the method used to calculate the safety. One method uses 1.25 another uses a more situational dependent value for safety. Anyway the value which goes in a table for the strength of the wood is the 95th lowest value needed to break that wood times a safety margin of 1.25. This is called a design reference value. It is specified in pounds per square inch for compression, tensile, bending and other types of stresses. An engineer will get these design reference values mostly from the National Design Specifications. Phew, I hope I explained that clearly enough.
Stresses become a lot more complex with wood than pounds per square inch applied in vertical compression. I don’t even want to go into it in this writing. Probably the best that the common individual can hope for practically is in calculating floor loads and roof loads on floor joist and rafters. Aside from that please go find a qualified structural engineer or copy very strictly some design that has already been engineered and tested. Where you might find pre-engineered designs? I have no idea, maybe a reader can clue me into this. One way might be to examine a structure which has been standing for 30 years and simply copy its design, making sure that you are using the same species of wood. Over-engineering can work where feasible. Use the formula variable P for Plenty. Though I think without a good measure of common sense and some prior wood working experience and some study, self engineering is risky business.
I think in my case if I do my own calculations for use of timber in a structure, the structure will either use timber only for a floor or roof, not walls and not for holding up the floor or roof. Or it will be for simple symmetrical one story designs, (Post and Beam).
Personally I still can’t help but love the look of timber frame. I can’t help but try to imagine how timber frame, or at least beams might fit into my own construction designs and projects. Some advantages in using timbers are.
- I can make my own beams.
- Fewer pieces are needed in the structure.
- The structure has the look of impressive long lasting strength.
- The structure is on display and can always be inspected for its integrity.
- Varying types of infill for walls can be used (Earth, Straw, Stone etc.)
Regardless of engineering complexity, I personally will continue to study how to engineer with wood. As I learn more, I learn more about what I may be capable of and when I must say, “Nope, we would need an engineer for that.”
A last note. I have been told the best chain saws are Husqvarna and Stihl. Husqvarna parts are easier to find I hear. Stihl has been recommended as the absolute best however. Saws of around 100cc or 10 horse power are best for milling lumber. Run them at 90% throttle if possible. Sharpen the chain often. Use good oil. etc. A special chain called a rip chain may be needed and can be purchased from grandberg.com.
If you visit Lee Valley’s web site you will find a wood working catalog and near page 200 will be a thing called a Beam Machine. It cost around $50. This is a very simple guide tool. It is shaped like a 2×4 in order to fit over a 2×4 so that it can slide back and forth along the board. This uses the board as a straight edge. The board would be nailed to the log. There is a C or U shaped clamp on the side of this bracket with 2 bolts. These bolts tighten up on the chain saw bar so that the chain saw bar is held at a 90 degree angle to the flat side of the 2×4. There is also a small bubble level on the bracket. The chainsaw bar is kept at a perfect angle as it is moved along. Once you get one side sawn, simply rotate the log 90 degrees and move the 2×4 to the flat side. Then saw of the next side of the beam. Repeat this 4 times and you have a beam. I am about to give this one a try myself soon.
Also at Lee Valley or grandberg.com you may buy the Granberg Mill. This mill would be a jig or frame that completely supports the chain saw. It supports the saw on both sides of the log. The top of this frame has rollers which roll along on the log or on a board which is nailed to the top of the log. The frame holds the saw a given distance beneath the rollers.
One of the more inexpensive type of highly portable band saw can be found at lumbersmith.com for around $2200. And one more tip, you may be interested in getting what is called a Log Arch for moving logs around your lot. This can be pulled behind a four wheeler. It moves one log which is chained up and suspended from the arch and boom. This can be easily made or purchased for around $700. I talked to a trucker from West Virginia at the time of this writing who told me that the going rate for Logs (as logs) were $0.30 to $0.45 cents per board foot. He said that standing timber would be about 40% of that cost. Personally I don’t intend to do the logging. And at least one author has agreed with me that if you are not a professional logger then its probably best to stay away from this. I do intend to fell some trees myself and cut boards/beams from the logs at the felling location. I might haul one or two logs per run sometime if I feel like it. I followed a 16 foot dump truck around Atlanta Georgia one day. He had a load of good sized 24″ diameter or better logs cut just long enough to fit the dump bed. He pulled a trailer with a bobcat and a stack of plywood. I assume he used the plywood to make a ramp for rolling the logs into the dump bed. He probably used ropes or chains and the bobcat to get the logs into the dump bed from a ramp on the side. I’m sure he used the bobcat to maneuver single logs into position for rolling up the ramp one at a time. If you are in a position where you might jump and run 24/7 think about finding some excavators. Excavators are constantly pushing down trees simply to burn them in dozer piles. They could possibly give you the logs/trees. They would even let you saw the lumber at the site most likely.
Stick Frame 2×4 2×6 2×8 construction.
I only want to say that the book, “Design of Wood Structures” covers engineering of this kind of construction really well. Engineers can certainly calculated the load bearing capacity of 2×4 walls. They can certainly calculate the load bearing capacity of various truss designs. A more modern type of truss design is the plywood or particle board I Beam. This is made by using a sheet of plywood that is say 20 feet long and only say 3 feet high. 2×4’s are nailed on each side at the top and bottom of the plywood. Joints are staggered. 2×4’s are nailed on each side over plywood joints. This is a strong truss for flat or near flat roofs and floors. When plywood and sheet rock is nailed to the 2×4 wall/ceiling/floor frame it is called sheathing and acts as a “diaphragm”. Both structural board (plywood and osb and particle board) and sheet rock act as a continuous brace for all parts of the frame. With close nail, screw or staple spacing (schedule), this forms a very rigid and strong structure.
Fasteners and Plates
The book “Design of Wood Structures” also covers plates and fasteners in very good detail. Plates are a fairly simple matter. Any stress on the metal plate will simply be trying to tear the plate and therefore puts it in tension. All one needs to know is the tensile strength of the plate for the given type of metal and thickness. Fasteners though are a lot more complicated. The book covers bolts, lag screws, screws and nails. Fasteners over 1/4 inch in diameter are large dowel type fasteners and need pilot holes or pin(bolt/dowel) holes. Fasteners below 1/4 inch in diameter are small nail or screw type fasteners and need no pilot holes. When using the larger type of fastener the computations and considerations become more complex. For example the strength of the member may need to be recalculated minus the area of the pilot hole or pin hole. Also angle of load to grain is figured into the calculations. Crushing strength of the wood members must be considered. This is why nails and screws are so popular. Some kinds of nails have greater withdrawal strength than others. Though in most connections withdrawal is not a consideration or much of one. Screws of course have the greatest withdrawal strengths.
All metal dowel type fasteners have a strength property know as yield limit. This is the pounds of force needed to bend the fastener. Actual shear or failure is not calculated because the fastener will bend or withdraw long before it ever breaks. Basically there are 6 modes of failure(bending and withdrawing and crushing) for every connection type. The engineer will calculate all 6 modes and use the mode with the lowest failure strength for the final value. It could work out that anyone single mode might be the lowest.
Anyway lets say you find that a bolt would hold up 100lbs as its lowest mode of failure. If you have 2 bolts then the connection will hold 200 lbs. If four then 400lbs etc. Same for nails or screws. Also washers and plates will prevent bolts heads and nuts from pulling through the wood member because they distribute the load over a wider area.
Of course there is more to it than this. Each calculation can be modified based on many different sets of criteria. For examples wet vs dry service. Moisture content of the wood. Repeated loading. Impact loads. Terrain modifiers. Occupancy categories and so on. There are factors for wind, snow and seismic loads. To thoroughly engineer the structure two different systems must be calculated. One is for lateral loads, called the lateral force resisting system. The other is the vertical force resisting system. In the lateral system sometimes walls and floors change roles. Yes joist and rafters become post. Lateral of course are wind and seismic loads. In an earthquake you have cantilever forces in play as if the ground was turned on its side 90 degrees so that it was vertical and the structure is hanging from the foundation like a shelf on a wall. In this wall/shelf example inertia is the force acting on the shelf (building) and not gravity. And in wind, braces may be in compression one moment and tension the next. Most homes are designed to withstand 80 mph winds.
Stresses or forces at play in a wood frame.
- Compression (crushing)
- Tension (pulling)
- Torsion (twisting, I only mention this, its not usually a consideration in wood construction)
- Shear (tearing, cutting)
- Bending (Bending Modulus or Moment, as in beams, rafters, joist)
- Modulus of elasticity (pliability)
- Cantilever (overhanging)
- Axial (along an axis, such as in post and braces)
- Self Straining (from shrinking)
- Creep (deformation from repeated loading)
- Deflection (bowing due to temporary loading)
In wood you need to remember that there are different values for all of these forces across grain vs with grain, and longitudal (top to bottom). The book “Design of wood Structures” covers all the do’s and dont’s when it comes to loads to grain considerations. It cover’s all other hard earned do’s and dont’s for just about everything that can be thought of. You might call these rules of thumb.
To keep things simple, lets say that the engineer is going to calculate the vertical force resisting system (vertical loads) of a wooden frame. He will divide the structure into minor tributary areas, then combine them along lines or points. Line being a joist or rafter, point being a post or brace. The forces actually flow from the very top of the roof down to the foundation in very much a similar fashion as water flowing from streams to creeks to runs to small rivers to larger rivers to lakes or seas or oceans. Tributary area is a great metaphor for describing flow of forces. And its a great way to break down the problem. Forces go from pounds per square foot on floors and roofs to pounds per linear foot on joist and rafters to pounds per square inch on post and foundations.
What software could one use? The mighty spread sheet would be the main tool. Special software for this purpose would have to be carefully made and certified by qualified people. I wonder if this is why you do not find free engineering software. Liability might be a huge problem when human lives are at stake. If I get time I will write some software for my own purposes for specific design problems but I probably will not be sharing it. Once a spreadsheet template has been setup for a given design problem however that one template can function again and again for different projects with little or no change. A good free spreadsheet can be found in “Open Office”. Simply google for “Open Office”, download and install it. They call the spreadsheet Open Office “Calc”. There is also and Open Office “Math” but I think this is only for constructing formulas visually for documents.
Types of Joinery that I have read about or heard of by name…
- Mortise and Tenon
- Open Mortise and Tenon
- Blind Mortise and Tenon
- Stub Mortise and Tenon
- Through Mortise and Tenon
- Step Lapped Rafter Seat
- Single Shoulders
- Double Shoulders
- Joist Pocket
- Lap Joint
- Through Half Lap
- Mortise and Tenon with Diminished Haunch
- Dovetail Lap Joint
- Lapped Half Dovetail Collar Tie
- Rectangular Tenon
- Square Tenon
- Wedged Dovetail Tenon
- Birds Mouth
- Soffit Tenon
- Housed Lapped Dovetail
- Half Lap Scarf
- Stop Splayed Scarf
- Bladed Scarf
- Beveled Edges
- Dressed Shoulders
Some ideas for lifting or raising..
- Shear Poles
- Gin Pole
- Block and Tackle
- Pike Poles
- Tread Wheel
Some tools of the trade
- Felling Axe
- Broad Axe
- Race Knife
- Boring machine
- Corner Chisel
- Draw Knife
- Riving horse/bench
- Scraping horse/bench
- Moisture Content Meters
- More Moisture Content Meters
Some of the names of the parts of frames.
- Collar Tie
- Cross beam
- Ridge Pole/Beam
- Front Plate
- Top Plate
- Summer Beam
- Corner Post
- Chimney Post
- Dragon Beam
- Major Purlin
- Knee Braces
- Jettied Post
- King Post
- Queen Post
- Hammer Beams
- Gunstock Post
- Joweled Post
- Tie Beam
- Ridge Beam
- Principle Rafter
- Common Purlin
- Anchor Beam
- Chimney Girt
- End Girt
- Full Plate
- Shakes (Wooden Shingles–3 foot Riven boards)
Common Design names
- Salt Box
- Cape House
- Two Story Colonial
- Banked Colonial
- Greek Revival
- English Barn
- Dutch Barn
- Hip Roof
- Gable Roof
This next set of photo’s shows the operation of the Grandberg Alaskan Saw mill. I am using my Husquvarna 55 with 18″ bar. It took about 30 minutes to saw off that first side. I was resting me and the saw a lot. It really moves along a lot faster than that. I bought two 10 foot 2×4’s for the straight edge. I intended to cut 10′ boards from this old dried elm stump. I realized after I finished that I really needed 12′ boards instead to hang over 1 foot on each end. However 9 feet or so is all the practical length I can get from this log.Next I intend to cut of at least one side or maybe both with a tool called the Beam Machine and my chain saw. Then I will cut 2″ planks from this log.
I demonstrate the use of the Beam Machine which uses a single 2×4 as a guide to cut off the side of a log. I realized after I started that I should have been 1″ further in. It looks to me like lumber could be made using this Beam Machine. If you didn’t want to use the lumber made this way for your home then it could always be used for barns, chicken coops and dog houses.
|Design of Wood Structures|
|Timber Framing For the Rest of Us|
|Timber Frame Construction|
|Old ways of working wood|
|The craft of modular post & beam|