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swindmill 06-11-2013 02:45 PM

Tearing up ground level deck to deal with drainage issues at rear of house
This seems like the most appropriate sub-forum, since it concerns a foundation issue...

I'm going to take up my decking and replace it but part of my objective in taking up the deck is to put proper drainage underneath, so I'd like to plan that before I start. The deck is no more than 10" off the ground, and I actually have no idea what's underneath it now, although my guess is mud. My house is over 100 years old, although the rear is an addition and has a concrete foundation. Within this part of the foundation is crawlspace, and the foundation does not go more than 12" - 18" below grade. I'm getting water in this part of my crawlspace, and I'd like to do what I can to remedy this. My guess is that the water is coming up from the soil, and I believe the only way to deal with this from the outside is perforated drainage pipe and gravel. That's about where my knowledge ends. If I'm correct to this point, I'd like some advice on what to do once the deck is torn up. I also have 2 downspouts that meet at the rear corner of the house, so I'd like to integrate those into the drainage system if possible. This is a shotgun style house, so the house and the deck are no more than 23 ft. wide. I guess my plan is to take up the deck; remove as much soil from underneath it as is necessary; put in a drainage system; and replace the decking. Any advice on how to properly put in this type of drainage system would be great. And if I'm totally off the mark, please let me know that too. The deck framing is in good condition, so I'm only planning to pull up the surface planks.

nealtw 06-11-2013 03:45 PM

The foundation will be sitting on a footing, generaly the perimeter drain will be at that level or below or atleast deeper than the fill inside the crawspace. If you have it dug up I would waterproof the foundation too, available at any lumberyard and the foundation will have metal ties thru the foundation for the form when it was poured, somethimes hard to find but there is a sealer for that too. If you can work it out run a seperate closed pipe for the down spouts. When you run them together the perferated pipe disperses the water around the foundation. There is also a special paper to put over the gravel under the fill to keep the mud out of the pipe. Lots of work, good luck.

WindowsonWashington 06-11-2013 04:24 PM

Whats the grading and gutter situation?

Most, not all, water issues that we see now can be handled with proper gutters and grading.

On those more indepth situations, they will require what neal is detailing.

swindmill 06-11-2013 06:55 PM

There's a gutter running the length of the back of the house, and it's fairly new and doesn't leak. There is a cap on it, which I think causes some water to run over and onto the deck. I will probably remove that. The addition has a sloped roof that runs up to the original roof, which is much higher. So, there are no gutters on the sides of the addition. I guess a picture could help, and I will post one if so.

There is not much grade to speak of. The lot is pretty much flat.

It wouldn't seem like much water would get under the deck if the gutter is performing well, but it seems to find its way there. When you step off the deck, which is about 8 ft from the house, you're on a paver patio with 6" of gravel beneath.

WindowsonWashington 06-12-2013 05:36 AM

What kind of cap is on it.

Most caps allow for overshoot in heavy rains and that can be a real issue with poor grading.

Ditch the cap like you are getting ready to do or get a much better cap that will capture all of the water all of the time.

swindmill 06-12-2013 11:25 AM

Here's a picture of the cap; I'm not sure what this style is called:

And, while I'm at it, here's the deck and anything else relevant to my questions:

WindowsonWashington 06-12-2013 01:48 PM

Ditch the cap.

That gutter is close enough that it could be easily cleaned and you are getting overshoot with that type of reverse curl system and you getting a bunch of water on the patio.

swindmill 06-12-2013 02:06 PM

OK. Ditching the gutter caps and I guess I'll look into digging a trench down the back side of the house and do the perforated piping and drainage rock. Would it make any sense to put some sort of waterproof material under the deck and grade it out towards the patio? Maybe a thick plastic or PVC liner? It won't be seen, obviously, and would take almost no time to put in place. That could help divert water that falls on the deck, even if it's only several feet further from the house.

nealtw 06-12-2013 02:37 PM

Anything that takes water away from the foundation is a good idea.

WindowsonWashington 06-13-2013 06:15 AM

I would start with the gutters first and re-evaluate the water issues.

You might be surprised that it fixes the issue from the outset.

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