I am a little wary of the job the concrete guys did in putting in our perimeter drain. A few observations/questions–they put in two pipe penetrations through the footing on either side of the back of the house since they were not sure where the sump pit was going. Of course, now we have an open hole through the footing in the unused spot. Isn’t this just a big opening for water to enter the rock beneath the basement floor from outside the foundation? The builder thought it would be a place for water to drain out–I think it is a place for water to pour in. Should it be sealed off or not? If so, how? There were several spots where the drain tile undulated up and down to the point where it was as much as 6″ lower in some spots. That won’t drain any water anywhere. They are going to fix that(or I will if they won’t). There were also spots where the tile was covered in concrete–that too will be replaced. Another question–at any spot where two pieces of tile needed to be connected, they just slit the tile lengthwise for about 6″, then folded over the edges and shoved it into the other piece. Is that OK? Seems like actual connectors would be more in order. Thoughts and observations?
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Replies
Doesn't sound too hot. But I'd say it's pretty typical of what I've seen.
If you're not happy with it, do something about it pronto. It's a whoppin' heck of a lot easier to fix now than a few years down the road after the house is landscaped.
The pipes running through the footing wouldn't bother me, as long as it was hooked up to the drain tile under the basement slab.
There are several here who believe it's a mortal sin to bring outside water inside to a sump pump. You may get an earfull about that.
Ambiguous headline: SURVIVOR OF SIAMESE TWINS JOINS PARENTS
It's OK to route the outside drains to a sump pump, so long as the sump pump IS NOT connected in any way to the sanitary sewer system.
What does the sanitary sewer have to do with it?To say he [Bill Gates] shouldn't own what he has is the same thing as saying Audie Murphy had too many medals and should've SHARED them with the bottom-of-the-foxhole crowd who never fired their rifles.
> What does the sanitary sewer have to do with it?
If lots of people feed footing drain water into a sanitary sewer then it creates a potential overload situation for the treatment plant during wet weather. In many parts of the country such a connection is illegal, and it will probably be illegal everywhere within ten years or so.
Definitely illegal to connect footing or gutter drains to the sanitary sewer in our area, for the reasons mentioned. I'll be pumping mine well away from the foundation. It's far cheaper to tell people not to put rainwater or groundwater into the sanitary sewer than it is to replace the hundreds of miles of combined sewers that cause the majority of the sewage plant overload problems here. But if the groundwater runs across your floor slab into a floor drain (connected to the sanitary sewer), I guess the city would think that's ok...
>>open hole through the footing in the unused spot. Isn't this just a big opening for water to enter the rock beneath the basement floor from outside the foundation
You do have a drain bed and tile under the basement slab? connect all perimeter penetrations to that interior tile. If not plug/cap the unused penetration.
>>it was as much as 6" lower
Bad, Bad, Bad. Level it! Or put a 1% slope to the opening/s going to the sump pump.
>>just slit the tile lengthwise for about 6", then folded over the edges and shoved it into the other piece.
Perfect. Uhm, they are going to put a gravel burrito around the tile aren't they?
A "burrito" is 6" gravel under and 1' gravel above the tile and the gravel wrapped, top, bottom, and sides in a piece of landscape cloth. Don't depend on just a "sock" on the tile.
You should also have a drainage plane next to the walls and cleanout/s for the tile.
>>There are several here who believe it's a mortal sin to bring outside water inside to a sump pump.
I compare that to putting a drip pan overflow in a visible location. It tells the HO there is a drainage problem before there is damage.
SamT
SamT- thanks for the note about the "gravel burrito"- I've always been a little suspicious about that filter sock on the drainage pipe.
I've got a clay till soil, and I'm planning to put on an addition with a full basement. I'll do all the good water-prevention stuff that I can with proper overhangs, gutters (we up here call them eavestrough), sloping the soil away from the foundation etc. But there's no obvious place to drain my footing drains toward. Our grade's pretty flat. Even if I do have the excavation contractor trench out a good distance with a decent slope ($$$ in extra digging), I think I'd need quite a long, deep trench to get enough surface area to actually take away any water which does get into my drainage tile. The gravel and back-fill around my foundation and under my slab will be so much more permeable than the surrounding soil, I'm sure I'll get water up against my foundation regardless what I do with sloping, gutters etc., so I expect the footing drains to actually work for a living.
Under those circumstances, is it still a dumb idea in your opinion to bring the footing drains to an in-basement sump pit and pump it out a good distance away from the foundation?
>>Under those circumstances, is it still a dumb idea in your opinion to bring the footing drains to an in-basement sump pit and pump it out a good distance away from the foundation?
Under any circumstances, is it always a good idea in my opinion to bring the footing drains to an in-basement sump pit and pump it out a good distance away from the foundation.
NO footing drain will last indefinately. The interior drain system is a very cheap alternative to excavating a basement wall later. Since ground water can and will rise underneath the slab, you need a way to get rid of it too.
With a drain to open air (which you don't have,) the sump switch should be just above the crossover holes in the footing. In your case, I would put the switch a couple of inches above the bottom of the sump pit, which should be a few inches below the bottom of the crossover.
As long as you already have a drain bed and tile, run a vent from the tile up to the attic for later installation of a fan to outside if Radon shows up.
SamT
D'oh! Sorry, SamT- didn't mean to mix up your point of view. It matches my uninformed gut feel in this case.
Forgive me for my ignorance as I ask you another string of dumb questions- I've never seen a sump pit being installed, and the construction basics books I've got don't have anything on the subject. What does the detail look like for the installation of a sump that the footing drains are connected to? How do you manage to avoid undermining the footings when digging the sump pit? What does the cross-over detail look like (i.e. how do you get the drainage under the footings to the sump- do you cast a deeper (thicker) footing in that area? Any need for additional reinforcement to keep the footing from cracking at the changes in thickness? And what's the typical sump made of?
Thanks for the sensible advice for a radon vent. The soils are very deep here-it's a very long way to rock, so I doubt there's much of a radon risk in my area. In the absence of radon, is there any benefit to sub-slab ventilation, or is a good, safe cover on the sump good enough? There'll be insulation and vapour barrier under the slab, and PEX tubing in the slab for heating.
I goota run to town for a little while, I'l;l; get back to you in an hour or so.
SamT
Here is part of a picture from:
NEW YORK STATE CONCRETE MASONRY ASSOCIATION VOLUME ONE NUMBER FOUR Recommended Practices for Residential Concrete Masonry Basement Construction
I don't have the link to this PDF but you can probably Google it.
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Notice that there is no gravel or tile under the footing. See also that the interior tile is lower than the exterior. It can be level with the outside tile IF EVERYTHYING IS CAREFULLY ELEVATED.
The sump pit is just a concrete lined hole in the ground. By careful digging you will be able to use the dirt as the outside form. Don't put a bottom in your form and hold it 4" above the bottom of the hole. Don't put a bottom in your form, allow the mud placed in the sides to flow under the form and hand level it after a couple of mins.
Rebar banding is recommended 2" down the sides and 2" in around the bottom. At least.
Design the form so the walls with drains come out first. Butt the drains tight to the side of the form and secure them from movement while you place the concrete.
A secret to easily removing inside forms; Lightly tack a thin (1'8-1/4") piece on the end of the form side where it meets the mud or the other side. When you remove the form that piece will be slicker than the mud and will be left behind. It will remove straight off easily. If you're using 3/4" ply for forming, butt the ends to 3/4" chamfer, which leaves a nice inside chamfer to your completed pit.
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For the pit cover, get a cast iron (child proof weight) grate. Build the pit to that dimension -2".
See Lip.gif. Tack a strip the thickness of the grate by 1 1/8" around the outside of the form. MAKE SURE that the top of the strip is level with the finished floor elevation. This gives you the finished pit concrete elevation and will leave a nice 1" by ? lip in the pit for the grate to set in. You can mess with the exact dims to work with what you have, just leave a little clearance 'tween concrete and grate.
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>>how do you get the drainage under the footings to the sump
Place pvc the same dim as the tile in the wall ON TOP OF THE FOOTING, or at the level of the exterior tile, which is above the footing and below the bottom of the slab.
SamT
Thanks, SamT- that's a great detail. Thanks very much for the forming tips for the sump which are really helpful and well illustrated! I presume you'd need an expansion joint between the slab and the sump walls where they meet, to avoid cracking the sump.
If I get what you're saying correctly: if I'm using 4" drainage tile and my slab is 4", and I've got 2" of insulation under the slab, I'd need the top of the footing set 4"+2"+4.5" = 10.5" below the finished floor height, so I can fit a piece of 4" PVC pipe (4.5" OD) on top of the footing but below the insulation/VB below the slab. That seems a lot lower than anything I've seen in the few excavations I've walked by, but I certainly haven't seen much so maybe I didn't notice. Did I calculate that right?
I did Google a bit before I posted my question to you, and found pictures of tile which appears to run right under a footing, which seems to me an absolute no-no because of the risk of a cracked footing down the line (unless you put a fair bit of rebar in the footing at that location). But it would permit you to keep the footing higher relative to the top of the slab (i.e. requiring less digging and concrete) while permitting the whole thing to stay dry, would it not?
You haven't built yet, so download this Form-a-drain spec sht from Certanteed.
They run the crossover thru the footing.
the way you already understand it works also, with a little more digging and concrete.
SamT
we really like using Form-A-Drain
Thanks for all the input. I did some further excavation this evening. What a joke of a job. In one spot, the drain is BELOW the BOTTOM of the footing, then it rises up ABOVE the TOP of the footing a few feet away. In places it is covered with fine silt, in others covered in cement, and at those goofy junctions, cement actually filled the pipe. I yanked it all up and threw it in disgust. Hell to pay for someone tomorrow. My builder is an older man, and wouldn't be able to jump down into the area where the worst installation is apparent to inspect it, let alone dig it out . Grrrrrrrrrrr.
When they replace the soil in those areas below the footing, it should be compacted to the same density/firmness as the rest of the soil under the footing.
SamT
Oh mannnnnn! I thought this was all taken care of, but noooooo. Raised a stink about my poor footing drain installation, and they tore it out and put it in correctly. It passed inspection on the first try, which is unheard of here. Well, backfill was yesterday, and I got there a bit late to see what was happening. Only the area inside the garage had not been filled. I saw a sheet of Typar over the rock(the rock that covers the footing drain) there. The builder had put that around the entire footing drain. We had talked about using "Typar", but I assumed he meant the filter fabric, NOT THE HOUSEWRAP! That would be the same as laying down a sheet of plastic. He used both permeable and non-permeable types, and I have samples of both here that have been holding a gallon of water for hours without passing a drop. Makes no sense. He says the gaps against the wall and below will allow water to get to the tile, but I say that silt will be forced through a small space and clog things up quickly. The Typar was to act like a silt fabric. So, with everything backfilled, do I make them dig it up and pull it out, realizing I risk tearing up my Tuff N Dri board in the process? My feeling is rip it out.
That's a new one on me - House wrap used as a filter fabric.
I'd tear it out if I was you. It may be a pain now. But it will sure be MORE of a pain 10 years down the road.You can do it anyway you want to as long as you do it my way first.
This Form-A-Drain approach looks like a perfect thing to combine with the ICFs I'm planning to use for the foundation walls.
Thanks SamT- you've been very helpful indeed. I can't thank you and the whole BT crowd enough for the assistance they've provided to me. Now let's hope that I don't screw up all these good ideas with bad workmanship!
Question: Why not just use a preformed plastic or concrete sump?
Builder called this morning and told me they were patching the unused footer hole with quickcrete, leveling the drain, and redoing all the connections with the correct connectors. They do wrap the drain in rock as suggested. I am using Tuff N Dri waterproofing/2" insulating board, and the soil used to backfill is a good draining sandy loam with a lot of rock in it. It pays to keep an eye on things!