dry laid foundation

I read in Jack Sobon's Timber frame construction book that using a dry laid foundation, there would be enough air circulation that the sills need not be pressure treated. Is this true? It seems that the stone would still sweat enough to rot the sills. Most of the old barns in my area eventually needed renovation due to rotted sills but these were all built on mortared stone foundations. Not that the building inspectors would ever let you build on a dry laid foundation, I am still quite curious. thanks tb

With proper air circulation timbers will last a long time. The barns you are referring to were probably 200 years old when they finally needed sills, right? PT won't last that long. Most of the damage I have seen at the sill and post bottom level has been from manure packed against it. Or from contact with the earth after a foundation failed. Again, the failure is after a couple of hundred years of frost heaving. I am going to be using a dry laid foundation on my next small shed. I don't know if you could get away with it on a larger building or not. If you look in Jacks book you will see different species of trees and which ones are suitable for decay resistance. Alas, there is no more chestnut, however we still have white oak. I don't even know if the new PT (ACQ?) is contact rated. I don't use any PT, plywood or other "modern" building materials. I did see a barn this summer that had a beautiful chestnut frame with bright green sills and repaired post ends of PT. Sorry to wander, but I think that nature will provide most of our solutions, we don't need wood that's been drugged.

DMS: Thanks for replying. Yes, the barns are at least 200 years old , some much older like the Dutch barns. They used the super dense old-growth trees for the frames and sills and I think that might have helped endure time. I did not know that pt does not last that long, but it does not surprise me. Buildings of modern society have crap craftsmanship and do not seem designed to endure time like the buildings of old. How long is pt expected to actually last??What to do ?? about building a structure(house) bigger than a tool shed, for which a building permit is needed, if you want to go without the "drugged" wood products like pt????It does not seem that there is an alternative to pt when framing to a masonry foundation???I have wondered whether placing a steel strip between the two would work?, but steel still sweats too, so it is unlikely. Steel is also quite expensive these days. If anyone knows of alternatives to pt for the wood to masonry interface, please let me know. Thanks. tb

I use 2-4" thick White Oak (all heartwood, no sapwood) sills with "Sill Seal" between the White Oak and the conventional masonry.

I understand your comments regarding ring density, but I am not certain if ring density in and of itself affects rot resistance.

Of course if you have a really dense piece of wood there will not be much sapwood, which rots easily.
-Collin

A friend of mine just finished the restoration/relocation of an old barn and he replaced the entire floor system with oak. Red oak for the joists, which were peeled logs with one sawn face, and white oak for the sills. The foundation is condrete wall with feildstone veneer on both sides, about two feet thick. The white oak sills rest directly on the foundation. The restoration was done by highly reputable company. I have seen the old PT rot away that was only five to ten years old. I have noticed that the "new" PT has a no ground contact warning on the label now. That kind of defeats the purpose of using it for the sills if you ask me. Hopefully someone with more PT experience will be able to post.

Dave

On the houses/barn homes that I have been involved with or crew uses White Oak sills on top of a stone foundation. However we cut 10" wide (1/2' under the sill width) strips of Ice & Water that is stapled to the bottom of the sill. I should probobly mention that the floor system is temporary supported at its level and final resting place, then the masons finsh the last 1'or so of wall.

I great book Listing rot resistance is Bruce Hoadley's - Understanding Wood. A must read for understanding the properties of wood.

Two years ago I met a guy in western NY who replaced a sill with the wood the client had on his property - Black Cherry! New 30'+ 10"x10" hewn cherry sill - My kind of repair.

Other than white oak heartwood cherry has good rot resistance so does black locust.

They used to use chesnut for sills in all the old barns/homes but you can't find that any more.

PT is a pretty genaric term. There are different treatments for different purposes. All of them require that you research them and discover what the manufacturer says they will do. I use copper napthalate (brushed on) on posts I am setting in the ground...mainly for the insect resistance.
I agree with the statement that it is usually neglect that has brought on the demise of the timber. Protect it from the wet dry cycle and it should last forever.

Hi all:

This Copper naphthalate, I wonder how much damage it is doing to the environment, as it leaches out into the water table?, as well as all the other rot retardant products.

NH

Hello all. Thanks for the info. The general consensus here seems to be that using a dense ,all heartwood, hardwood(namely white oak,cherry, and black locust) in conjunction with some form of sill sealer is perhaps the ultimate connection, In addition to meticulously making certain to protect the sill and frame from the elements. Right??? I still find it hard to believe that any building inspector would let you knowingly build like this(without pt). Has anyone had any trouble with the codes on this technique? Inmy area the codes are pretty strict(Woodstock,NY), as opposed to the more secluded desolate Western parts of the state. Just curious, Has anyone been able to build on a dry-laid foundation while still abiding to the codes of modern times???

northern hewer
I only offered the copper napthalate as an alternative to some of the known to be bad treatments. After doing some research I came across it and if some of the manufactures and federal testing of it is to be accepted then it is a relatively safe product. Check out one of the sites at http://www.merichem.com/products_services/wood_preservative/index.php
an older treatment was to char (burn) the post, and white wash is known to keep fences good for years (probably the lime)

I looked through my Sobon books again last night and he does suggest dry laid foundations if you have the ambition. However he does point out that there may be a building code catch. I am taking a workshop with him next week at Hancock Shaker Village and will discuss the building code issue with him if I get the chance. I know he has built several buildings in my this area that were on dry laid foundations, so I think it may not be all that far fetched.

I am building my second outbuilding on a dry laid stone foundation. My building department (North Greenbush, Rensselaer County) had no problem with it whatsoever. Sills on the first one are white pine (white pine heartwood is moderately rot resistant). The one I am working on now has all-heart white oak. Jack's new barn, being written about in the last two issues of Timber Framing, also has white pine sills.

Similarly, my TF addition and garage have white oak sills (2" for the garage, 8" for the addition) on poured concrete. Again, the building department had no issues with the lack of PT.

I don't know what the building department would say if I wanted to build a larger structure or house on a dry stone foundation...

FWIW,
Dan

Another important way to extend the life of your sills is to get them up out of the splashing rain. Often it won't look right, but if you can get the sills about two feet off the ground they will stay a lot dryer. Also, allow plenty of space between plantings and the building to allow good air circulation.

Modern pine sure is weaker and a lot less rot resistant than pine from 200 years ago!

I talked to Jack today and he said that you can build a residence on a laid stone foundation as long as you use mortar, and your building inspecter allows it. I don't know what luck you will have in NY, however. It would seem that non residence buildings do not have to meet the same requirements. I hope that helps.

P.S., the workshop with Jack and Dave Carlon is AWESOME!

Hi folks,

I like the concepts of borate rods, although you'd need a lot of them. So long as you can keep access to inspect the holes periodically to see if the rods are being dissolved.

I'm a long way away, but our city building code (which follows UBC and IRC, pretty much standards) allows for pressure treated OR rot resistant species. Seems like a person could always put a 2X plate down below your sill of some exotic, such as Alaska yellow cedar, purpleheart, apatong, etc.
Many of these woods easily surpass PT in their longevity.
We have a great building department, and it seems like if you can make a very sound argument for deviating or improving upon code you can get the signature in red ink. Maybe you'd be as lucky...

All the best,

Zach

Naturally rot resistance species are accepted by the NYS code (and in Woodstock.) I reviewed some timber frame drawings for a fellow in Columbia County with a dry laid stone foundation. When finished with the stone work he called for his foundation inspection and the Building Inspector stood there scratching his head. He then signed off on it, and the rest was history. I think if you use a mortared wall you could even get away with it in Wdstk. Anchoring the sills to the foundation with embedded anchor rods would be required.

Thanks Christopher,do you suggest only white oak because white oak is quite expensive and it seems that we dont plant it much anymore due to its slow growing nature. Also my sills need to to be quite long which seems more difficult to obtain for white oak as opposed to pine. Where are you located in relation to me in Ulster county because I am looking to find an engineer that I could consult with about a Dutch barn on lime mortared foundation I plan to put up in Saugerties,NY(just East of Woodstock, with slightly less ridiculous building codes). I have some design questions regarding a few adjustments to the traditional New World Dutch barn(anchor beam) design. Based on reducing the proportional dimensions of the usual 45-50 feet width to 30-36 wide bents. I will eventually like to have an engineer approve my finished frame plans that I plan to draw myself. Does that sound absurd?? Perhaps there is a way we could get in contact and I could better explain my situation. Thanks again tb