# How do I prevent water from collecting against side of house?

Our house has a concrete patio (I'd say about 12' x 10') in the back that is very slightly angled in so that rainfall can cause water to collect where the patio meets the back wall of the house. What are my short-term and long-term options for addressing this?

The only thing I could think of would be to elevate/resurface the patio near the house to redirect the water away from it. I'm a beginner DIY'er and am not sure how exhaustive of a procedure that would be.

In the meantime, I'd like to make sure that the exterior of the house doesn't become water damaged. Is there a sealant I can use to protect where the patio meets the house? Caulking perhaps?

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In the short term, you could waterproof the foundation with some sealant paint like Drylok.

Longer term, you need to fix the problem by directing water away from the house. Is there cracking where the patio meets the house? That would indicate subsidence at that side of the patio, at which point I would definitely call in the professionals.

The next question is how much of a slope there is, and how much you would need to build up the house side of the patio. A thin layer of concrete is easy to apply; you just need to get it thick enough that it won't flow so much that it levels itself out before setting. Getting it looking good is more difficult, but can be done with care, but again you're balancing time to do that versus the concrete setting as you're working with it. If this is someplace that people will use a lot, so you want it to look good, you might still want to pay someone to do it.

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@Niall - Thanks. I don't see any cracking but there's caulking between the patio and house that looks a bit old. I'm thinking I should replace that too. The exterior of the house is stucco -- would Drylok work for that? – Mike B Oct 20 '10 at 20:50
The Drylok web page mentions stucco. I've never seen (OK, noticed) caulk used like that so can't say for sure if it's OK to do so. – Niall C. Oct 20 '10 at 20:57
Rather than building up the patio on the house side, you could also lift the patio (concrete lifting) so it slopes the other way, but that's a job for a pro. – Eric Petroelje Oct 20 '10 at 21:00
I'll need to check with a level but I don't think the slope is much at all and as far as I can tell, it hasn't changed -- there aren't any tree roots or shifting ground that I can see. Is there a particular reason why adding a thin layer of concrete on the house-side of the slab wouldn't work? It seems to me like that would be the easier and more cost efficient. – Mike B Oct 21 '10 at 15:52
@MikeB: I believe it will work, otherwise I wouldn't have proposed it. I don't have any downvotes, so nobody disagrees (or has yet). This question is still getting a lot of views and activity so maybe you should wait for a while and see what else happens here, be it more answers or comments on the existing ones. – Niall C. Oct 21 '10 at 19:07

If the cost of raising the patio is too great you could get an angle grinder or perhaps a better choice would be renting a concrete wet saw and cut out a strip about 6 inches wide from the edge that meets the house wall. As @woodchips points out in his comment, make sure you wear gloves, safety goggle and a mask for this. It'll get hot, but it's very dusty work and the saw will throw up chips of concrete.

Remove all the concrete and put in a gutter that will collect the water and direct it away from the house to the drains.

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Instead of an angle grinder, which assuming we're talking about the same tool has a maximum cutting depth of just over an inch, I'd recommend renting a concrete wet saw for this. And instead of a gutter, I'd install a french drain: en.wikipedia.org/wiki/French_drain – Mike Powell Oct 21 '10 at 14:32
@Mike - good point on the tool - I'll update the answer. – ChrisF Oct 21 '10 at 14:38
Be VERY CAREFUL when you use any saw on concrete. Inhaling concrete dust can cause lung problems (silicosis) that will kill you. So use a dust mask on anything like this. – user558 Oct 21 '10 at 15:41
@woodchips - yet another reason to rent a wet saw -- no dust. :) – Mike Powell Oct 21 '10 at 15:45

Water laying against your house will cause any number of problems. You DO want to deal with this.

If this is a single slab of concrete, there are several options to deal with it.

1. Leave it alone, pretending it is not an issue. This is not a good solution, but a surprisingly common one. Applied sealants will NOT keep water from getting where you don't want it to go. And water sitting there for any period of time will cause rot, mold, bugs, all variety of things you don't want.

2. Tear it up, and replace it with a properly sloped pad. Yeah, that will make you unhappy when you pay the bill.

3. Mud-jacking, where a professional drills small holes into the slab, then (slowly) injects material under pressure through the holes. This causes the slab to rise up in a controlled manner. When the injected material hardens, your slab is now properly set to move water away from the house. A good contractor can do this without cracking the slab at all.

4. Cut the slab away next to the house, and run a drain that will pull the water away. Don't expect this to be a cheap solution, and even if you do the work yourself, it will only work if the water has someplace to go. That may involve a sump pump, a bad long term solution (IMHO) because pumps always fail when you most don't want them to do so.

I'll bet that the mud-jacking solution is the most economical one, as well as the solution that will leave you most happy. Find a reputable contractor.

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+1 for Mud-Jacking. – Tester101 Oct 21 '10 at 14:10

I assume you're getting a noticeable depth of water in a puddle against the house. We've had similar problems at our house, and they're pretty common around our area. You really should deal with this because it can cause all kinds of problems, like damaging your foundation. I also assume you have wood studs and supports somewhere behind the stucco, and if that gets soaked by standing water, it can rot or warp or do other damage.

Short term, you can get an electrically-powered utility pump and pump the water away. I've done that using an inexpensive 1/4 hp manual sump pump and a garden hose. You can find them at home centers or on Amazon, and they'll suck a puddle down to a small fraction of an inch. The downside is you have to be around when it rains to start and stop the pump manually. (For what you're doing, don't want an automatic pump with a float; they're designed to work in holes that fill with water, called "sumps".)

Long term, a lot depends on what things are like around your house. We live on a slope with a lot of "hydrostatic pressure", so our long-term solution was putting in a French drain uphill from the house to route the water away. Friends of ours used to live in a lowland area, and their rain problems happened because the water table would rise and flood their lawn; the solution was to dig a French drain, drop in a huge sump pump, and pump the water away. Since you're not super-experienced, I'd call a pro.

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I have encountered a similar situation in a house I am buying for my elderly parents. The house has a concrete pad up against the house that connects to the asphalt driveway and has no slope. The adjacent basement wall is bowed 3". A licensed foundation expert indicated the hydro-static pressure caused the wall to bow. He recommended the concrete be removed and re-poured to slope away from the house as well as ensure all downspouts are directing water away from the area. The thing I'd be concerned with in regards to concrete lifting (slab jacking) is the fact there will probably be re-bar installed to fasten the concrete pad to the house. In my case the seller is covering the expense so I'm happy with the concrete replacement option.

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Slope the ground away from the house, forget the paint.

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The patio is the reason for the water collection, can you revise your answer to address this? – HerrBag May 22 '13 at 15:40

My current home has a walkout basement that had a concrete slab for a patio. The rain gutters were too short allowing the rainwater to back flow against the basement wall. This also caused the dirt against the house to settle several inches below the concrete slab. The sump pump would eventually remove the water, but that was not a good situation. What I did was buried and routed the downspouts to the back of the yard and rented a jackhammer and broke up the concrete, which had also cracked. I then sloped the dirt way from the house and added patio pavers. I think it looks nicer, and the whole thing only cost me about \$600. I have absolutely no water issues now.

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I had a terrible problem of water accumulating next to my house on a small concrete slab just outside the garage side door. However, the water turned out to be coming from an A/C + heat pump outside unit which had been placed on another concrete slab on top of the first one. The bottom slab did not have the correct slope (it angles ever so slightly toward the house, instead of away).

The inspector had a simple solution: insert a shovel, using it as a lever, to hoist up the upper concrete slab (on which the AC unit rests) on the side toward the house, where the water was running down, and then insert an appropriate sized piece of wood, stone, or whatever other strong material. We did so, and it only took about 2-3 inches of lift on the side of the house to make the water drain away.

We are now very happy, as the water drains away from the house, and without spending any money at all.

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