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"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
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These sites are helpful:
http://www.exteriorwood.com/htm/toc.htm
http://www.mcvicker.com/twd/gwdi97/page015.htm
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I am a homeowner with two exposed doug fir beams that always seem to be in need of repair from the sun and the weather. I am sick of painting these beams and fixing the dry rot every 2-3 years.
Can any of you recommend a better way?
Galvinized caps?
Better Paint?
Bondo?
Cut the damn things off?
Thanks in advance for all your replies
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Greetings David.
I have been involved in few residential wood foundations but can give a little advice for all it's worth.
The economics depend greatly on where you are going to build and what financing you will need.
The most critical aspects of this construction is the founding of the base plate, drainage around the foundation, waterproofing membrane, backfilling with sand and not allowing vehicles to park or pass near the finished foundation.
Regardless of what you have heard, I have seen these walls deflect 1 to 3 inches on a regular basis and have inspected one for a client that the wall on the side of the driveway had to be excavated and replaced.
Be as careful as you would with any building project and take nothing for granted.
Inform yourself and you should be allright. This is better done with people in your immediate environment due to local weather and soil conditions.
Hope I was of some information
Gabe Martel GSC
Project Manager
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DAVID,
I'LL TAKE A SHOT AT A FEW THINGS I'VE LEARNED AND HEARD.
1. MAKE SURE THE 6 MIL WRAP IS CONTINUOUS FROM ABOVE THE FINISH GRADE TO OVER THE FOOTINGS AND ALL SEAMS SEALED TIGHT WITH GOOD OVERLAP.
2. FROM WHAT I'M TOLD THE TRADITIONAL CONCRETE FOOTINGS WITH THE WALL BOLTED TO THEM IS BETTER THAN USING A WOOD FOOTING ON A GRAVEL COMPACT.
3. MAKE SURE YOUR STRUCTURAL ENGINEER KNOWS WHAT THEIR DOING. I KNOW A GUY THAT WAS TOLD TO USE 2X8s FOR A 10' WOOD FOUNDATION. THE HOUSE IS 4-5 YEARS OLD AND THE WALLS ARE BOWED.
4. GOING ALONG WITH GABE, DRAINAGE IS A BIG FACTOR. I'M NO SOIL EXPERT BUT I KNOW THAT IS A BIG FACTOR.
5. ON THE GOOD SIDE - IF DONE RIGHT THEY ARE EASIER TO FINISH (IN MY OPINION). CAN BE REPACED IN SECTION FOR MAJOR DAMAGE. AND IF YOUR A GOOD CARPENTER MORE INEXPENIVE TO BUILD.
6. FINALLY, WHATEVER YOU DO MAKE SURE IT'S DONE RIGHT. THEY CAN BE A NIGHTMARE IF SOMEONE DOES A SLAP SHOT JOB.
I'M NOT SURE WHAT CODE YOUR UNDER, YOU MIGHT LOOK IN BOOK 2 OF THE UBC STARTING ON P.59. IT COULD HELP (FASTENERS, H2O PROOFING, ETC).
SOUNDS LIKE A GOOD FBH ARTICLE, PROS AND CONS OF WOOD, BLOCK AND POURED FOUNDATIONS.
*David, I'll take a shot here, too. I've not only built several treated wood foundations, but I've inspected several as well. My two-bit opinion is that they can,indeed, be a reasonable way to go assuming they're built correctly, but can fail quickly if not done right. Get a publication called, "The All-Weather Wood Foundation System; Basic Requirements," also known as Technical Report No. 7. It's put out by an outfit called the National Forest Products Association (I think they may have changed their name, tho). The last phone number I had for them was 202-463-2700. This is the publication refered to as THE reference by the Uniform Building Code. Many carpenters, figuring they know how to frame an above grade wall, assume they can just as well frame a wood foundation wall. But there are some major differences, especially when the wall gets over 4' high. If you get the book, referenced above, read the whole thing, don't just look at the diagrams. There are a few nuances such as fluid pressure of the soil and whether or not there is uneven backfill against the foundation (as in the case of a daylight basement), that will affect the way the wall is built.The problems I see most often are these: 1. Studs are too small or spaced too far apart. The studs bow inward.2. Studs are not well attached to the top or bottom plate, or do not have metal connectors that are required for deep fills. The studs split and just slide off the plate, or the nails shear or bend off. 3. The tops of the walls parallel to floor joists are not restrained by floor blocking and/or metal connectors. The walls bow inward.4. The bottom plate is not well anchored to the concrete footing. The plate splits at the bolts. 5. The plywood is too thin to span between joist, causing it to buckle inward. Some recommendations: 1. Spring for SS nails rather than the dipped galvanized they call for. 2. Waterproof with a better material than the 6mil poly they call for. 3. Provide a good perimeter drain, just as for a conrete foundation. 4. If you're building a basement, restrain the bottom of the wall with a concrete slab poured inbetween studs or against a screed board. Do not just bolt the wall to the top of the slab.5. If you're building on a crawl space, use plenty of anchor bolts or add a separate, treated 4X bolted to the footing to restrain the bottom plate and bottom of the studs.6. Use good, clean backfill material. Drainage is especially important with a wood wall. 7. Don't assume just because a guy is a carpenter, he necessarily knows how to deal with wood foundations. Quiz him or get him the Tech Report.Tom Laing
*i have built both prefab, american standard homes.and site built a.w.w.f.in the past 20 years.as long aS YOU LEAVE ADEQUATE DRAINAGE AND PROPER LUMBER SIZING AND SPACING YOU WILL LOVE THE SYSTEM. I LIVED IN MINE SINCE 1980 in southeastern ohio and wouldnt use anything else for my next one !!as far as expenses , they are more costly, because of the drainage needs. the floor should key into the walls and the floor joists alsoshould key to the walls.a good vapor barrier is also necessary!good luck!!!
*Is it necesarry to use PT or rot resistant (RR) studs and top plate for building these foundations if PT or RR sheathing, bottom plates, and screed board are used?
*Tom,As you seem to be knowledgable on the subject, I thought I would ask you directly. Is it necessary to use PT or rot resistant (RR) studs, headers, cripples, top plates, etc., if I used PT or RR bottom plates, screed boards, and sheathing? Also, You mentioned in your reply to David that a better waterproofing method than 6 mil poly should be used. What do you reccommend?Thanks,Britt Smallwood
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Yes Yes Yes
In building a wood foundation the enemies are moisture and vermine and insects and mold.
They don't care where or what part of the wall is their next meal.
Your question about 6 mil poly.
I recommend and use bitutene type membranes instead. They are made by several manufacturers but all are peel and stick applications. Go to you building product supplier and ask them what they carry and look over the specs. and then make up your mind if you can affort the extra protection.
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Britt, Although I think most of your questions have been answered, I'll add this: Everything below grade and to at least 6" above grade should be PT. Often you can get away with an untreated top plate or very top plate. On general principles, as well as according to Codes, you should assume that some type of leak could develop, so think of it as insurance, if nothing else. On the waterproofing; I would recommend what we call Bituthene, here in Alaska. Although I think the actual name is "Ice and Water Shield." It used to be made by W.B. Grace Co. It's 40 mils, as compared to the actual Bituthene, which is 60 mils thick. We use this because the local supplier has chosen to carry it, but there are other good products out there.
Tom Laing
*I have a contractor built wood basement. Despite internal bracing with 2x4s and a joist and plywood floor before backfilling, I got about 1/2 inch deflection from plumb on one long wall. The rest of the house I'm doing myself, so I have built interior partition walls against this bowed wall in hopes of stopping further movement. This is a summer cabin, now closed for the winter, so I won't know for a while if movement has stopped. Now my next problem--I want to pierce one wall to take my sewer pipe out to the septic tank about 30 inches below grade, but I am worried about leaks. I'm thinking about installing one of those roofvent flashing devices on the outside wall, running the pipe through that, and calking around the pipe. Any better ideas? Alternative is piercing the wall above grade and then dropping to my septic tank line. Many thanks to repondents.
*William,I don't think there's a "one size fits all" answer to your question... there are some variables which could affect the solution. Such things as a high water table in your area, the presence or lack of good backfill and a perimeter foundation drain, the slope of soil near your foundation will determine the best approach. If your site is dry, and sloped away from the building (gutters are good, too), there shouldn't be a problem sealing the pipe going thru the wall. There are a number of good products for this (see your local supplier or foundation contractor). If the wall is waterproofed already, be sure the product you use is compatible with it. Some products tend to eat each other up over time. I'd stay away from a roof jack. The galvanizing will eventually give out, and the steel will rust, and the neoprene collar will have enough flex that it will probably be compressed under the weight of backfill and the seal will be lost. Be sure you compact the soil under the pipe before filling over it.Tom Laing
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Does anyone have any advice, caveats,
etc. about wood foundations?
TIA
Davi