Determining if a french drain will work or not?

[rswyan]

I have the exact same problem. With every heavy rain, I end up with the corner of my basement damp and sometimes, noticeably wet. Above the area of the basement that's always wet, I have a large trex deck (approx. $16k worth) so tearing it out to do any extensive work is not even an option. The slope of the terrain underneath the deck is fairly flat.

Problem numero uno .....

You need some slope to move the surface water away .... because if there is no slope it is likely going to percolate down into the ground (.... and your basement)

My question and what I've been contemplating is clearing out the small amount of weeds, laying down a weed barrier, and putting down enough river rock to gradually slope away from the house, maybe a couple inches worth.

I'd be less concerned about a barrier for weeds and more concerned about a barrier for the water ..... the latter may serve to function as the former, in addition to being a barrier for the water.

 

[rswyan]

I'm no geologist - but I would bet you are dealing with hydrostatic pressure forcing water in from beneath the slab and footing.

I'd say that's entirely possible .....

Given what you describe, unless the water comes down the mountain and accumulates in your backyard, saturating it - I would doubt the surface runoff is your issue.

It may well not be - the point was, if it is, handle it - because while surface water may not be the predominant or primary issue, it certainly doesn't have much potential to help the situation.

Solving a specific drainage problem will often have multiple aspects that need to be addressed.

Especially if the surface is hard - I would assume the majority would just run on past your house and continue down hill.

The undisturbed soil away from the structure could be hard as a rock ..... and the backfill up near the house could be a loose mess ..... or even a different soil type .....

If the runoff was the problem I would expect that walls in the affected area to be damp/seeping as well - depending whether they are block or poured. If the breach is only at the cove joint (where slab meets wall) then most likely it is due to hydrostatic pressure.

Valid points.

Without see some pics or personally having observed the amount of flow coming down we're all flying blind to some degree here ... myself included.

 

[NuBota]

rswyan - I don't disagree with one thing you said - you are 100% correct. The only thing i would debate, lightly, is that both methods are essentially an effort to divert water away from the foundation - otherwise it is simply a matter of where the diversion occurs.

The problem is that you may not always be able to effectively address the issues from the outside. In my area, the water table is pretty high - so much so that many communities were not allowed to build houses with basements - depending on the year/decade they were built. Many communities were also built on swampland that was filled in. Add to that poor grading by the builders where water problems in one lot affect the surrounding ones. All which support your points about poor planning and incompetence - but it is not always possible to correct those issues later.

My limited experience is from the few years I did this for a living some 20+ years ago. We did some houses that were 50+ years old, never had water problems, no changes on the outside - then a problem occurs. Somewhere water found a path underground to the foundation.

The most memorable thing was when we were doing a house in a community that was 30+ years old. The house we were doing, we did the entire interior perimeter - about $6K with a lifetime warranty. Same house model up the street hired a company to do the outside perimeter (same week we were there) - $30K, no warranty. They came down to chat - and were crestfallen about the price - but still felt they would have the problem resolved - we were there a year later....

On another one - the house was in a low spot in the neighborhood. During the spring, the entire yard was persistently (weeks at a time) saturated like a soaked sponge - walking on it caused water to percolate up over your boots. When I cut through the floor we saw the water basically under the entire slab. Had to dig a temporary sump to pump it out before we could proceed. Funny thing was - after 24 hours of pumping - the entire yard started to dry up as well.

To your point about electricity - again you are dead on. But unless the water problem is severe, this is generally not an issue. The trench and sump can generally hold the water until power is restored.

In "grandma's" case - she always had a wet floor after any significant rainfall - prior to the system being put in. This past fall, her house caught fire (cable company, drilling a hole and hit the panel). Five months no power, lots of rain and snow - the system contained the water. Granted it was full up - and caused dampness in the air - but no water on the floor.

It really boils down to severity of the problem, level of effort, and expense. Obviously easy external fixes - gutters, downspouts, etc- should be addressed. But if it gets more complicated than that - you need to decide best course given the situation. In the OPs case, if he only has a little bit of water, in one corner, a 3ft sump and pump alone, in that corner might be enough to handle it.

Not advocating one method over another - just providing some alternatives

 

[NuBota]

rswyan - looks like we're cross-posting - again, I agree 100%

 

[grossgary]

i would rather not do indoor even if it means more work/cost.

the gutter downspout goes right down the corner, right into the ground, right above the inside corner that leaks into the basement. is that something to look into?

i'm starting to think that maybe the deck just needs to come off and do this right, dig all the way down to the foundation rather than guess.

i'll do some more inspecting and post some pictures, i'd rather do this right the first time, time is not something i have loads of and i'd like it done right.

i'll try and get a feel for the original drainage system, spec's, and pictures for you folks. informed oppinions would be awesome.

thanks again.

 

[dave1949]

The above may well be true - and if it is in fact the case, it's probably the absolute worst thing that could have been done - the contractor that did it ought to be shot from guns.

Think about it: In essence, one is taking surface water (which is nowhere near the foundations when it arrives on the roof), and could be easily moved away from the structure with a hard pipe ..... and then routing that water down into what I would assume to be a perforated pipe (otherwise what would be the point ?) around the foundation ......

My guess would be that every hole in that perforated pipe does not have a one-way valve on it ......

I don't disagree with how it should be done. OP said there is one drain pipe going to the creek - as far as he is aware anyways. Could be another that is covered up and who would know where to find it? The gutters go into pipes in the ground. Unless there is a grey water system somewhere, it's dollars to donuts the gutters are tied into the footer drain. Even if that makes no sense, it was done a lot in the past. It would be a good first step to re-route the gutters no doubt.
Dave.

 

[dave1949]

i would rather not do indoor even if it means more work/cost.

the gutter downspout goes right down the corner, right into the ground, right above the inside corner that leaks into the basement. is that something to look into?

thanks again.

Now, that is useful information :laughing: Looks like a good idea to solve that issue step one.

I wouldn't rush into tearing off the deck until you can exhaust all the other little remedies that may work. Unless you want a new deck of course.
Dave.

 

[TeamNH]

.... If you did do it inside, you could put your sump on the down hill side of the house and just have a gravity powered pump.... needs no electric. Thats how my house is setup... works great and no need to worry. I see how an good inside drain system would work great in some areas, but I think in some area's other methods would work better.

I have surface water problems, my house is build into a mountain like yours. I just put in 500' of pipe, with stone in a trench and tied in all down spouts. I only used the triple walled pipe or schedule 20. None of that black drain tile pipe. This way I could have solid pipe getting the water 20' from the house before it opens to the trench for going into the ground. A local builder told me the pipe is in the trench for insurance, if the trench takes on too much water... the pipe will pick it up and move it. Other then that your trench is moving the water and the stone is there to help just the water move thru. It poured today... and my system worked perfectly. Now I just have to finish grading and my surface water problems are gone!

So I guess what I am saying is there is 5 ways to get to the same place. Try to look and find the exact cause. Surface water? Ground water? Water building up and being forced thru the block? Once you figure this out... your solution will present itself to you. You might find yourself in need of doing both an outside trench/swale(for surface water) and an inside sump system(for ground water).

 

[grossgary]

Pardon the length. Thanks to all your feedback, you guys are amazing. I postponed the French drain I was going to dig on Monday. Seems I should get a better feel for what痴 going on. Here痴 some pictures and a description that might help you guys.

The deck photo shows the grade leading down to the deck. On the far right edge of the photo is a GUTTER going into the ground at that corner of the house, you can't really see it in the photo but it's there. That closest corner of the house is the corner that leaks in the basement.

I checked that gutter out today the gutter does not appear tied into the foundation drains. It turns away from the house within about a foot of the surface using black corrugated pipe 3 in diameter is my guess from memory.

** This is the same corner that is leaking in the basement. Although the gutter is on the side and the leaking tends to be along the back wall, not the side wall where the gutter is but same corner, clear as mud?

 

[grossgary]

This close up picture has 3 red boxes in it is the side of the house. This is the side adjacent to the deck, that youæ±*e facing in the é›»eck photo. This first, closest GUTTER is the same one in caps referred to in the last post/photo.

The lower red box shows the GUTTER going into the ground it turns 途ight as seen in that picture about 1 foot under the surface.

The middle box is the concrete stairs going down to the basement. Thereç—´ a drain cover going into plastic PVC piping at the bottom of the stairs just before you enter the basement.

The top box is the front gutter which goes right into the concrete. The concrete is actually holding it in place so I couldn稚 remove it, but I would assume it痴 going away from the house like the other one, but who knows. I only know of one drainage into the creek so I知 not sure where those gutters drain too finally. Maybe they have drains in the creek I値l try and check, I致e never looked closely before.