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Question DetailsAsked on 5/13/2013

Who should I hire to repair flooding garage?

Do not know if it is a simple French Drain or whether it needs waterproofing on the foundation slab.

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I am assuming from your question that you are sure it is not from a broken pipe. You do not say if you are new to this house and so have no idea of the cause, or if you have lived there awhile and therefore this is definitely a "new" condition. You also asked if it needs waterproofing "on the foundation slab". I hope you meant foundation wall not slab - if your horizontal slab (garage floor) is leaking then you either have a broken pipe under it, or a very high water table. If that is the case, there is no waterproofing you can do to stop the inflow through a slab - you have to get the water level down in one of several ways, as indicated below.

So, next thing is to tie down the cause - the water could be from roof runoff not being carried away from the house, ground slope around the house leading toward rather than away from the foundation (possibly due to settlemetn ove the years of the backfill around the house), high water table, any of the above previously remediated by a french drain that has become plugged or frozen, excessive watering near the foundation, or a water pipe leaking (either service pipe or maybe an outdoor faucet that froze and broke, or automatic watering system or weep hose applying too much water).

1) If roof runoff (or pooling from a downspout) inflow will obviously peak in the day or so after significant snowmelt or rainfall event, and be non-existent in dry periods. Will generally (unless you have very porous soil) be associated with roof runoff ponding along the foundation wall. It might be leaking in through cracks and pinholes in the foundation wall, or if ponded high enough, even flow in over the top of the foundation, at the base of the wood walls.

2) Leaking pipe or faucet you can easily check out - walk around outside of house looking for water coming out of a wall or over the top of or through the foundation wall, or a concentration of water at one point when it has not been raining, without an obvious source. It is not at all uncommon for water service lines to break right at the house foundation wall, because of settlement of the foundation puttin gload on the pipe. If you think it might be a pipe leaking at one point, use a stethoscope or make a cardboard cone (about the size of a traffic warning cone and use it like an antique hearing "horn") to listen to the slab, foundation wall, and earth outside - if you have enough of a water pipe leak to come through your foundation you should e able to hear it. of course, make sure no water is running in the house at the time.

3) Automatic watering system or weep watering system you can look for and make sure it is off or not over-watering. Generally, you should not be applying water within 3 feet or so of the foundation. If you need to water closer than that it should be by hand, and severely limited to only that needed by the vegetation, not deep soaking.

4) If you know you have a french drain, you can try putting a running hose down the cleanout and see if it flows freely out the outlet (or into the sump pit). If not, you may have a partial collapse, infiltration of roots blocking it, it froze, or (rarely) it plugged up with iron or sulfur or lime buildup. A sewer and drain contractor can clean that out, and most can run a color (be sure to specify color - costs little more than black and white, but shows the situation MUCH better) camera up the drain pipe to see what is happening.

5) If it is sewer or septic backup you should know that from the smell, plus the infiltrating water will normally turn the area black and moldy even on concrete and brick, whereas straight water leaves only water stains and maybe a bit of white lime deposit on concrete or brick, though it will black mold on concealed concrete/brick and on wood and drywall surfaces.

6) If you have running or standing surface water within about 10 feet or less of the outside of the house, then you need to get surface runoff redirected away from the house by regrading and compacting a low-permeability sloping surface away from the house, and/or diverting incoming surface water with a swale or ditch at a distance if you can not do it by changing ground slope at the house. Only if you cannot physically divert surface water away (house is backed up against a hill or in a cut, for instance) should you rely on a french drain and foundation wall waterproofing. Usually you can get rid of at least most of the surface runoff by regrading or putting in an impervious or paved surface swale or curbing. It is very common to go through all the effort of installing a french drain and waterproofing, then find the water level is still so high that it starts coming up along the edges of your basement slab (which generally is NOT bonded to the foundation walls, and it is VERY expensive to do so properly even on new construction). In fact, if you have high water ground water, a french drain that does not freely drain to a lower elevation (as opposed to into a sump or wet well) can aggravate the situation, because it provides a direct route to the foundation, and the surrounding gravel acts as a reservoir right next to your foundation. In that case you may have to put in an outside wet well sump pump, and also put in one or more sumps and sump pumps through the interior slab, or in extreme cases a perimeter drain cut in all around the edge of the slab, leading to interior sump pumps.

7) If you have high water table only after snow melt or heavy rainfall and the level drops rapidly as water runs off or soaks in, then foundation waterproofing treatment may take care of the issue.

8) If you have high water table for extended periods, or if rainfall and snow melt stands for quite a period, then you may have a low permeability soil layer keeping it from soaking in, or you may just be at such a low elevation relative to surrounding drainages that the water table is near your ground level. To see if this is the case, look around at where nearby lake, pond, stream, and road ditch water levels are relative to your garage floor level when it is leaking. Also ask neighbors if they are having problems or have had to install drainage control or waterproofing. If you have a chronic high water table situation, sump pumps in basements/crawl spaces should be common in your area too.

9) Basically, foundation wall waterproofing will only keep your floor dry if the water supply is limited, so the water is basically filling up the soil voids in the looser soil along the foundation wall and weeps through the wall a bit, but there is not enough water to saturate under the foundtion and leak in under the foundation wall and up through the slab joint (which commonly sits 1-6 feet above the bottom of the foundation wall, depending on normal frost depth in your area). If you are getting a lot of water, it is year-around, or the water table is higher than the bottom of your garage/basement slab, you will get leakage even with excellent waterproofing. Typical bitumastic waterproofing is really designed as a water repellent - it is not designed to totally waterproof your wall and make your house a boat, does not extend below the foundation footer, and it deteriorates and starts leaking over time, needing redoing every 20-40 years.

10) Therefore, if you have a lot of water contact due to an uncorrectable surface water or high groundwater issue, then in addition to the waterproofing, you have basically only one option on an existing house - a french drain at the foundation wall footer level, preferably free-draining to some lower elevation away from the house (or to a sewer, if that is allowed in your area, which is rare); or if you are down in a hole, draining to an outdoor wet well or sump well away fromthe house, where the water is picked up with an automatic float-controlled pump and piped away to a safe disposal area.

You have two routes you can go to approach this problem - after eliminating the first few easily checked out possibilities above, you can talk to a drainage and waterproofing contractor (who of course will tend to recommend significant waterproofing and/or french drain construction), or you can first spend about $300-500 to have a civil engineer experienced in site drainage issues come out and look at your situation and run a rough set of levels and maybe a couple of shallow auger holes to see what your surface and groundwater drainage situation is, then design a fix. This costs more up front, but has a better chance of solving your problem than a hit and miss "let's try this and see what happens" approach.

Answered 7 years ago by LCD


Waterproofing foundation

Answered 6 years ago by Gnanette

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