Foundation Advice

[WCarlson]

I finally broke down and had an additional detached garage contructed to house the off season vehicle and my ever growing collection of implements (back hoe, snowblower, MMM, FEL, forks, box blade, 18 horse DR chipper, log splitter, boom pole). It was completed today and is 24' x 30'. It is located on a sigificant grade (about four feet over the 30 foot dimension). It is frame structure with T-111 siding built on two courses of block on a 3000 lb cement slab with varying additional block courses to ensure that the portion of the building below grade is block, not siding. In order to preclude water penetration and frost heave, I plan on placing perferated pipe covered with landscaping cloth around the building with one foot of small gravel agaist the block everywhere the block is below grade prior to filling the excavation. I have two qustions for the experts on TractorByNet. First, do I need rigid insulation between the cinder block and the gravel? What else should I do to the below grade foundation, if anything?
Bill

 

[OkeeDon]

We have a small cabin in the mountains of North Carolina that we pruchased from the original owners. Part of it is embedded in the hillside. It was always wet inside the walls, to the point where water would actually run. A section of subfloor and the first three floor joists were actually rotted from the moisture.

We had to make some other repairs, so we had a trench dug around the entire cabin, all the way down to the footer. After the repairs were done, the contractor laid perforated pipe, landscape cloth and gravel at the bottom. Then, he coated the entire portion of the block walls that were in the ground with a black tar-like waterproofing, probably roofing cement (I wasn't there when he did the work), and then stuck a layer of visqueen over the waterproofing , then backfilled.

The inside of the walls has been dry as a mummy ever since. That was about 14-15 years ago.

 

[Junkman]

The best thing to do is to get below the floor level all around the building and put in the perforated rigid PVC pipe. I would first put down a layer of 3/4" stone and put the pipe on top of it and put the fabric on top of that. If you can find the fabric sock that would be best and then put the landscape fabric on the top between the stone and soil. Paint the entire block surface below ground with roofing tar that is applied with a floor mop. I would also use 1" blue Styrofoam below grade to keep any friction from the block. Run the drain pipe to a lower part of the ground and try to keep the entire line below the frost line even if it means an extra 10 or 20 foot length of digging. You want to keep as much moisture away from the slab and walls so there is no chance of frost heaving. Ideally, this should have been done before the slab was poured. I like to have the drains under the floor if possible also. Also, taper the ground around the building away from the building and also divert any roof drains away also.... DO NOT hook the roof drains to the perimeter drain, but you can put solid pipe in at the same time and use that to bring the roof water away to the low spot..... Good luck with the project and if you need additional information, please don't hesitate to ask for help.......

 

[theonlybull]

i'll second what's already been said, except that it's foundation coating, not roofing tar, that's rolled on the wall. it's like tar, except that it's a little thinner, alowing it to be applied alot easier.

 

[WCarlson]

Junkman,
I'm slightly confused. Does the foundation coating go on the masonry or on the polystyrene foam blue board or on both?
Bill

 

[Junkman]

20 years ago, we used roofing tar..... don't know exactly what they use today. What ever it is, dress as if you were going to the moon, because it doesn't wash off very easily. Throw away clothes also.... now onto the question. You coat the block and allow it to dry for a couple of hours to days..... depending on the product. Then you put the 2' x 8' piece of blue Styrofoam in either vertically or horizontally. Just make sure that you get the tongue and groove correctly oriented on each board. You back fill just enough to hold it in place. Be careful not to put any rocks larger than your fist against the foundation or within 24" out from the foundation. It is large rocks that cause the problems when they start to move due to the frost. I learned all this when I was working for a building contractor one summer. Back then we didn't have Styrofoam, but we did all the other things. Twenty years ago, when I built my house, I added the Styrofoam after reading about how it was used in Canada to keep cellars warm. At that time, MA was requiring all new house foundations to be insulated because of the energy crisis. I also thought it a good ideal and it has worked well for me.........

 

[WCarlson]

Junkman and theonlybull,
Thanks, as always on TBN, I understand a lot more than I did. Using the internet I have found that there a lot of products for foundation waterproofing available. Now I need to pick one and get on with the project before the snow hits again.
Bill