fish_antlers
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The Truth is Out There
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posted September 01, 2003 04:31 PM
 Edited By: fish_antlers on 1 Sep 2003 17:32
QUestion about foundation of a house (for an expert)
For someone here who might know.. we have a house and it is built ontop of solid rock/granite,,, the foundation has no footing so the foundation walls sit directly on the rock. (we just moved in btw) .. noticed some water in the basement and dug up the uphill side of the house to investigate, discovered that there is no footing and that when they poured the walls they didnt clear all of the debris in places so the actual foundation wall has spots where water has erroded small 2" or so gaps underneath (the space between the wall and the bedrock that was filled with debris...)
question... to stop the water prob will pouring a footing against the existing foundation wall on the outside sufficiently seal it against the bedrock provided I actually clean it up properly?
thanks
   
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zxrcy
Novice Class
Posts: 62
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posted September 01, 2003 05:52 PM
Foundation
Hi Fish!
Yikes ! There is no really fool proof solution. In a normal house the foundation wall is damproofed so that it sheds water down the foundation wall and around the face of the footing, draining into the soil below the footing and therefore not the basement. If drainage is poor you put weeping tile around the perimeter at the level of the bottom of the footing. The weeping tile is then connected to a field drain. In your case it sounds like you have a couple of problems.
First the footing should have been poured tight to the bed rock to create a seal. Then the damproofing on the exterior of the wall should have been supplemented by an asphalting or pvc waterproofing membrane bonded to the wall and extended onto and bonded to the bedrock. This should have extend up the foundation wall by about 3ft. This is cheap to do when the house is being built. Then to stop water pressure forcing water under the wall weeping tile should have been extended around the bedrock side (all sides if it completely sits on bedrock) then lead away to an area drain somewhere away from the bedrock.
Just pouring a curb against the existing wall I don't think will solve the problem.
Where is the water coming from. If it is subsurface lateral drainage (spring, sideslope water course etc) then the water needs to be diverted around the house with weeping tile and the curb by itself definitely won't be enough. If it is surface run-off running down the wall, then pouring your curb and adding a water proofing membrane may work.
Once the wall is dug up I would waterproof and put in tile. It's peanuts compared with the damage of a leaking basement. Unfortunately contractors in the housing industry are not very well informed when it comes to building science issues and usually go by rules of thumb and what worked last time. The contractor should have asked someone about how to waterproof a basement in the presence of bedrock.
I am an architect and extensively renovated my house last year using a contractor. The contractor is a Certified Master Builder and he was installing windows with the building paper/tyvec and flashings in the wrong place. I showed him the manufacturer's literature and how to do it properly, he couldn't believe he had been doing it wrong for years. . said everyone does it the way he was doing it. Now he does it the right way. . . at least he was willing to listen & learn.
You may have to get a little tough with your contractor to get him to fix it properly. It might be worth your while to pay an architect or other knowledgeable building professional for a few hours to come and help you out and talk to your contractor. Good luck.
Email me if you need any other help with this.
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fish_antlers
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The Truth is Out There
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posted September 01, 2003 05:57 PM
Thanks zxrcy...
Okay... here are some pix.....
This first pic shows part of the area I am digging up.. .as you can see they filled it with sand etc and then paved over it, but the water just gets trapped under the concrete.... Also the bedrock is very angular/ jagged so there are lots of places for the water to get trapped.....
This next photo shows the foundation and how it is on the granite.. you can see where it has been eroded away and there are gaps between it and the granite... basically there was just loose dirt in those places that I dug out.. .in otherwords the contractor etc was too lazy to properly prepare the site and dig right down to the bedrock so these small pockets of debris ended up in there and allowed the water to pass between the foundation and the bedrock...
This picture shows a closeup of a cavity left by the debris.... note that to the right of my finger there was debris so the foundation isn't in contact with the bedrock... also note that to the left of my finger the foundation makes a perfect seal against the bedrock...
One of the probs is that the bedrock is very angular/ jagged so Creating any sort of seal would mean I would have to at least pour that level?
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zxrcy
Novice Class
Posts: 62
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posted September 05, 2003 11:18 PM
Is the water surface run off or is it percolating through the bedrock formation?
If it is surface run off between the two houses you might be able to clean all the organic shit out from under the foundation wall. Then pour the conc. curb against the existing foundation wall. Water proof it. Then dig out the space between the houses. Put in a run of sloped perforated drain pipe leading out to the back of the house to a field drain, or somewhere out to the end of the garden to take the water away from the house. Then back fill over the pipe with gravel up to the level of the adjacent ground. You want to create some way of getting the water away from the foundation wall quickly. If it was nice smooth bedrock you might get away with just sealing the foundation to the rock with concrete but not with a broken formation at an angle as you seem to have. The water will just go through the cracks in the formation.
Where is the interior floor slab in relation to the foundation wall?? Your site looks like it slopes. Is this the uphill side??
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swft
Needs a life
Full throttle!
Posts: One MEEEEEELLION
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posted September 06, 2003 12:09 PM
Hey Fish,
Guess you got what you paid for, eh? 
Seriously tho, good luck with the repairs!
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fish_antlers
Administrator
The Truth is Out There
Posts: 21895
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posted September 06, 2003 05:34 PM
actually we still got a HUGE deal.. if only you knew how much houses were worth around here! Shitty thing about it is even though we had an engineer inspect the place he cant look under the ground to see what peopl ehave done...
not a big deal now... I bought a cheap chinese cemetn mixer for $400 cdn and we poured over 70% of the repair today...
it's goning to rain so we'll have to hold off on the rest but we seem to be winning!
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worm~hole
Needs a life
Miles to go before I sleep....
Posts: 10623
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posted September 08, 2003 04:58 AM
you buy cement mixel flom halbol fleight?
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