I’m looking at a new construction house in pottstown pa. The home is 4,000sqft and a full walk-out basement. It’s a lovely home, but It has a feature that I’ve never seen in a basement before. The walls are 9′ poured concrete and the slab has about a 2″ gap that runs the perimeter with gravel up to 4″ from the top. When I questioned this, I was told this was a french drain and it is used to ensure moister is carried away from the house. I mentioned that I wanted to finish the basement (it’s large). I was told to put in a vapor barrier and frame to the inside of the slab. Is this legit? I’ve never seen a slab not poured all the way to the walls?
Government’s view of the economy could be summed up in a few short phrases:
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.
Replies
The control of water and moisture should be on the OUTSIDE fo the house.
I would be asking LOTS of questions.
Makes it sound like the builder did not have any idea of what he was doing.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
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The control of water and moisture should be on the OUTSIDE fo the house.
I would be asking LOTS of questions.
Makes it sound like the builder did not have any idea of what he was doing.>>>>
oh, really ?
to me it sounds like the builder has an exact idea of how he's going to control the situation..
i've always done my water / moisture control from the inside
edit : actually , that's not true... my first two houses used the exterior approach..
but exterior approaches do nothing for high water tables ... i build crawls and full basements with the assumption that we are not building a boat, and something is going to leak.. so we have to control the leaks... ergo: an internal drain system.. which also doubles as a potential future radon mitigation system
most exterior french drain systems are installed wrong and serve no purpose other than to spend money on a stupid detail that hasn't been thought thru to a good conclusion
but hey, whadda i no ?
Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Edited 7/15/2008 5:50 pm ET by MikeSmith
"but exterior approaches do nothing for high water tables ..."How do you have a high water table with a walkout basement?Although he did later correct that to 5 steps, about 3 ft. It still does not sound like a high water level table."which also doubles as a potential future radon mitigation system"How do you control radon coming from under the slab with a 2" gap in the floor.The only reason that I can see for the gap is if they expect water to run down the inside of the walls. I have nothing against having an UNDER THE SLAB drainage as a backup. But it needs damp proofing and water "direction" (I won't use water proofing) on the outside to direct water to a drain..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I have seen interior drain systems used before, but here in East Tennessee, they are not that common. An exterior drainage system makes more sense to me too, my reasoning is that if the water table is high enough to activate your sump pump below grade, then the probability that hydrostatic pressure is exerting a negative effect on the foundation and footers seems high. Think about it. The water has already reached the foundation and gotten below the footers before it can enter the interior drain and exit via the sump pump or to open air. It seems to me that the freeze/thaw cycles could potentially wreak havoc during the cold season. Let me clarify that I am no expert, and here in the Southeast clay soil makes for an excellent drainage material. Your situation might be different. A little re-grading and run-off management seems to have gone a long way for me so far. Only time will tell.
Edited 7/15/2008 8:45 pm ET by arcflash
Depends on the location, and on local codes.
Your description sounds like standard fare where I formerly lived (northern Ohio). The 'french' drains facilitate the use of a sump pump. Proper installation (and maybe a battery back-up) of the pump will ensure that your basement stays dry, except in the most extreme conditions.
Of course, here in the sandhills of North Carolina, the builder would be villified for even suggesting any basement, of any design.
Politics is the antithesis of problem solving.
It's sub-slab radon pressure relieving construction. Take a few deep breaths and stop worrying about the gap at the edge.
Is there sub-slab drainage to downslope daylight opening? Have you had any water issues in the basement? Terrain - flat or sloped (the reason you have a walkout basement)?
One thing you can do is tape a square foot or yard of poly sheet to the floor and another to the wall, then check for condensation under the poly the next day. If you have it, then you have to be very careful how you finish the basement. http://www.buildingscience.com has some useful discussion of what to do or not to on finishing basements. Start there. Others will give 2 cents worth behind me.
Thanks to all who have responded. It does run to a sump. As to the battery back up I don't know, but I'll check into it. I plan on a whole house generator. I'll have to talk to a building inspector I guess. It just flies in the face of my common sense (assuming mine is good) from where I came from. I did drywall construction back in my college days and it just seems wierd to me. It seems with the open area between the slab and wall, you would be letting in moisture?Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.
Is there any possibility that you have expansive soils in that area and they do this to allow the slab to move up and down?.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
What you describe is done in just about every basement here and is not called a french drain, but a "floating slab" btw "here" is upstate NY
Jeff
I also live in upstate NY and we do similar. We also use exterior drain.
We do run it to a sump pit though.
Piffin we are sane also but our motto is better safe, than have to come back.
Edited 7/16/2008 10:43 pm ET by frammer52
Yes, we also run a footing drain outside, all of it connects to the crock if you can't get to daylight. Amazing that every builder here must be a hack according to some. Just regional differances.
I couldn't believe the harse statements, especially when it is custom and works in different parts of the country. I wonder if we should tell them that we don't put vapor barrior under concrete anymore?
No, don't tell them.
I think they will think we are absolutly crazy!
"It's sub-slab radon pressure relieving construction. "So by having the gap it reduces the pressure of radon that would otherwise be trapped under the slab and allow it to free flow into the house!.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I was going to edit in a smiley face, but I was busy getting my tongue unstuck from the inside of my cheek.>>"It's sub-slab radon pressure relieving construction. ">So by having the gap it reduces the pressure of radon that would >otherwise be trapped under the slab and allow it to free flow into the >house!
you and I are the sane ones here.But I ain't so sure about you.;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"you and I are the sane ones here."Hey watch it.Just because I am right this time does not make me sane.I demand that you take that bad.I reserve the right to be insane..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
OK, you are in sane.So what does that make me since I agree witcha?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks again to all. I saw posts both "walk away" to "it's no problem" I've spoken with others in the neighborhood and it's not uncommon. The sub-div is new. So new that the final paving is not done on the roads. I'm still going to pay for a home inspection (company dime) to insure it's kosher. Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.
French drains were popular... stress on the word "were".
Definately have the radon checked before finishing the space, because the only way to mitigate is sealing the drain.
30 or so miles to the south of Pottstown, french drains are very common.
However, I see your post indicates a full walk out basement - so an exterior foundation drain to daylight could have been incorporated.
I would check around the locale to see how common the practice is in Pottstown.
The flatter the land and denser the homes are sited the less common exterior foundation drains become.
To produce a gravity operated exterior foundation drain for my home, I would have to pipe the water about 600' - into the next subdivision! I do not think the neighbors would like that!
Needless to say, I have a french drain with sump pump as do at least 70% of the home I work in. Some sumps are normally dry, others pump frequently.
Don't panic - check around.
Jim
Your just the man I want to talk to. The walk-out was an error on my part. It's a walk up. You exit the basement and go up about 5 steps. The drain in the bottom is connected to the sump. The sub-div is on high ground and my back yard slopes to a drain system that flows very well away from by house and is on public sewer. In all the house looks to be very solid in all areas. As I mentioned doing construction years ago (20+) I had never seen this in my neck of the woods (Southern VA). When I finish the walls do I put a vapor barrier on the back side of the wall and insullate then drywall the inside? As to the radon, the test will be conducted as part of the purchase. I'm a corporate relo so the company is picking up the tab. I plan on making the basement my home theatre and was curious how to handle the walls. I plan on treated for the sill and stud walls tile the floor. Government's view of the economy could be summed up in a few short phrases: If it moves, tax it. If it keeps moving, regulate it. And if it stops moving, subsidize it.
I'm down the road about 50 or so miles and that is the way we were required to do the basements for years and years.Now we put two inch pipe thru the footers every so often to the 4 inch base of clean stone, which has a 4 " perforated pipe around the perimter under the slab (which goes tight to exterior wall,no gap) which ties into the sump pump pit. I guess the theory is that you are never going to keep all the water out, so what comes through (and relives pressure behind the walls) gets pumped out. After reading the post, this seems to be a regional thing.
a lot of panic stricken people here.........
we are just north of you (Allentown) and this method is not uncommon. we more often see a corrugated plastic piece attached to the foundation wall to allow any moisture to drain down.
the 2" gap thing is somewhat of a headache though.
if your radon numbers come back high, that gap will need to be sealed at significant expense. what if the radon count comes back ok today, nothing is done, but high 5 years from now after the basement is finished you get high readings ?
you should check with some neighbors to see where they are.
are you absolutely sure that a 4" interior underslab footing drain was installed on the interior ? very important. you can check the sump pit to look for the pipe outlets.
carpenter in transition
what they are telling you is that they have no confidence whatsoever in their ability to properly seal the foundation wall properly and to provide a perimeter drainage system.
I would bet money that hey failed to install any perimeter drain at all, opting for this cheaper alternative.
And they assume that water in that basement will flow down, but what goes down can also well up in some instances.
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I thought they were now called
"Freedom Drains"
Any place I have ever lived a french drain is not as this OP described, but is always a shortcut to doing it right, usually a quick fix after the original has failed.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
This is not a true French drain. This method assumes that water will weep in through the walls and drip into the channel, and be carried away by a pipe below. Water weeping through the walls will eventually weaken the walls of the basement and therefore the foundation. A true French drain is where the water is intercepted before it reaches the level of the basement slab. A drainage pipe (leading to a sump pump) is placed at the level of the footing and is covered by gravel and a cloth that will not allow fine sediment to clog the works. Then it is all covered by concrete.
Johnny