I just poured the footings and foundation walls for a new home with basement. My concrete contractor says that if I run drain tile around the insides of my footings and under basement slab, I do not need to run drain tile around the exterior perimeter of my footings.
Any advice?
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Replies
To kyeser,
Thats a new one on me. If you put them to the inside, where is the water going to go? Most water penetration through the soil has a tendency to sit on top of the footings of the foundation. Through hydrostatic pressure it can find its way through the footings and under the floor slab. I would think the reason for putting drain tile on the outside would prevent any water from penetrating your foundation and footings. Ive seen this in an area where I worked, (the foundations were never sealed, no keyway on the footing and drain tile on the inside) even with gutters and down spouts water always came in at the joint where the foundation met the footing and the drain tile was on the inside. There was no place for the water to go before it reached the inside of the crawlspace. I would recommend that you place them on the outside and direct the drain tile to a sump pump.
You always need the drain tile on the exterior to handle groundwater and rain, giving it a place to go BEFORE it gets into the house.
IF you have a high water table making water well up under the house, yoiu should also have an interior system with a sump and separate from the exterior system.
Of course, this may not apply if you are building in Death valley. Other than that, I would begin to ask myself, it this guy is trying to take shortcuts now, what other problems will I have with him. Could be he's a great carpenter but just doesn't know much about water penetration and foundations.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Your concrete contractor read his This Old House or Hometime notes wrong. Tell him to go back and watch the video tape over again and reread the Home Depot Manual. As the others have stated - drain tile is used to PREVENT water from getting IN/ UNDER the house. If you are building over an underground stream, then yes, you must ALSO install some sort of draining system under the slab to get water out.
Maybe your concrete contractor shouldn't be eating while watching TV. It's harder to take notes and the coffee spillage smudges the ink.
Har, Har, Har! I couldn't help myself.
This is a serious mistake though, which illustrates a complete lack of understanding foundations. Very scarey. No offense, but I hope you misheard him.
we've never put a drain tile on the outside... here in the land of clay soil ( acshally glit.. which is glue & sh*t )
we've always put my drain tiles on the interior.. course.. we first put down a bed of 3/4" crushed stone..and then run the 4" pipe around the interior of the footing... or no footing if we pour a 12" wall..
for the last 15 years or so we also put two risers up so we can use the same tile system as a radon removal system ( hey , i don't believe in it either... but sure do get some grateful owners who get a negative radon report down the road when they try to sell)
our tile system either leads to daylight .. or to an interior sump and then gets pumped out..
built our first house in '75 and we've never had a wet basement
exterior tile systems do nothing for you if you have a high water table and the water comes up from below.. and exterior tile systems tend to clog over the years unless you can keep them protected with a filter fabricMike Smith Rhode Island : Design / Build / Repair / Restore
Right, if you have a high water table or an underground stream. But that's in addition to an exterior drainage system.
If you only provide an interior drainage system, what happens with the roof runoff? Or when there is a heavy rain? By having the footing drainage system on the exterior don't you prevent hydrostatic pressure against the foundation wall? Isn't the intent to keep the walls/ foundation dry? With your system, it seems as though you are bringing more water under the slab just to have to get rid of it. In other words, with the drainage system at the interior of the foundation, water has already permeated through the footing and probably the foundation before it can be diverted.
We have not been building since '75 but we customarily install the same as you but on the exterior side of the footing and covered by salt hay or recently, fabric. We also install a pipe through the footing at a few locations to relieve any hydrostaic pressure beneath the foundation slab.
Please explain to me what I have been doing wrong or don't understand.
nothing wrong that i can see... exterior french drains just never mad sense to me...
neither do gutters.. good grading at the foundation will direct most of the roof runoff away from the foundation..
any water that gets thru the foundation or under the foundation will rise until it gets into the interior pipe system... then it flows by gravity to daylight or the sump...
where do your exterior french drains lead to ? Mike Smith Rhode Island : Design / Build / Repair / Restore
Our drains lead to daylight.
Grading is not fool proof during heavy rains.
I'm not comfortable with waiting to address the water drainage until after it is under the slab. What's out, stays out. It's enough to drain whatever is under the slab without introducing more.
No gutters? I can't respond to that.
frankie... a high water table ( seasonally ) willl come up universally.. not just on the out side of the footing...
dry basements are our specialty.. never had one fail..
also... how can you always lead your drains to daylight ? there's gotta be some that you couldn't...
here... we can't hook up groundwater / roof drains to town sewers..Mike Smith Rhode Island : Design / Build / Repair / Restore
Mike you seem to be more of the old school New England on this one where the thinking is, "You can't stop it from coming in so you might as well wait until it does to deal with it."
I prefer to keep it out in the first place. That secondary interior system is for rising water that comes up from under.
If you let the water go all the way down through the soil and then under the footing and then up into the interior drain, you encouraging a lot of hydrostatic pressure which is not good for the walls in winter or for the roots of shrubbery or other plantings.
.
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Well stated. Thank you Piffin! I'm out.
Edited 12/29/2002 9:15:00 PM ET by Frankie
bs....
we backfill with gravel... we don't have no stinkin hydrostatic pressure..
what we do have is water tables that go from 3' in the spring to 7' in teh summer..
if i did it you guys way... i'd have a lot of heaved slabs and wet furnaces..
hah, hah, hah...Mike Smith Rhode Island : Design / Build / Repair / Restore
I got no problem with that, Mike. You got rising ground water. That is what hydrostatic pressure is BTW.
In your soils and water table, I'd be doing both interior and out..
Excellence is its own reward!
"The first rule is to keep an untroubled spirit.
The second is to look things in the face and know them for what they are."
--Marcus Aurelius
Mike -
Relax. Go back and read the earlier posts. We do what you do AND we also install drainage around the exterior. It would not cause heaved slabs and wet furnaces. At worst (from your perspective) it's redundant.
I have always respected your comments and pretty much see stuff as you do. We all have our own methods that work for us. The only reason I asked you was that I'm always thinking there might be a better way or reason. Maybe it's the type of soil you have there. I dunno.
As for where does the water go, it depends on the municipality. Some make you provide a dry well, while others let you dump into the catch basin, and sometimes you get lucky and there's a hill and woods behind the house. It's mostly a pain in the ars.
F
frankie... what , me worry ?Mike Smith Rhode Island : Design / Build / Repair / Restore