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.

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.

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.

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.

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.

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:

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.

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.

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

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.

I got the deck up and realized the deck isn't attached to the house, which I should have assumed, but it changes my plans a bit. Because the structure goes down so low, I can't grade away from the foundation and lay plastic. The only way I can see this being possible is if I were to put a retaining wall where the edge of the deck meets the patio now. Any thoughts or ideas on what I should do would be appreciated.

I included the other picture to show an old drainage pipe of some sort that is sticking out of the ground near the foundation. This is an addition, so that would have been about 10 feet from the original foundation. I currently have all PVC drainage lines, so I'm assuming that whatever this is, isn't connected to anything. I thought it was odd that it was open. If I look down at it, it turns down to the left with no blockage. Thoughts? (The white thing to the left looks like it broke off the top of that drainage opening. House was built about 1900)

So the deck is sitting on the 2x10 that is not rated to be contact with the ground? Get some hooks, chain and some turnbuckles and chain the AC unit to the roof rafters and lift it off the deck and pull the frame of the deck out of the way.

I'm replying to my own post as I think...but, one thought I've had is to run the plastic between the joists and the rear deck foundation, which sits mostly under the dirt. I'm pretty sure I could do this if removed the nails that are toenailed from the joists to the deck foundation. Maybe cut through there with a reciprocating saw. With that loosened up, I could slide the plastic between there and it could run from the foundation to the patio. One weakness would be the screws that I'd have to toenail back through the plastic, but I'd think the water through there would be negligible.

nealtw said:

So the deck is sitting on the 2x10 that is not rated to be contact with the ground? Get some hooks, chain and some turnbuckles and chain the AC unit to the roof rafters and lift it off the deck and pull the frame of the deck out of the way.

Click to expand...

I really wouldn't know if it's rated that way or not, although I'm guessing you would. It appears to be regular pressure treated. I could probably dig out the dirt that's in contact with it.

EDIT: There are 4x4's in the ground with concrete holding those 2x's.

It looks like they constructed it and then put the dirt right back.

I'm learning about deck structure as I go here, my deck structure in particular. What I've found is that there are 4x4's approx. every 6 feet with 2x8's bolted to them. The 4x4s are held in the ground with cement, but it appears that after the 2x8s were bolted to the 4x4, concrete was then poured around the 4x4, locking the 2x8 in with it, if that makes sense. Here's a picture below. I tried to rinse off the concrete so you can see it, but didn't have much luck. There is basically an ~18" radius of concrete around each 4x4 and the 2x8s are set in the concrete as well. I can dig the dirt up that touches the 2x8s, but it would be an enormous amount of work (which I'll do if I should).

Without knowing what rating was bought it would be hard to tell. Usually anything rated for underground or ground contact has been incised for better penitration of the treatment. Incising is the knife cuts that you will usual find on all sides of the 4x4s and 6x6s.
The deck is way underbuilt, a single 2x8 is not enough and no beam at the other end, even Mickey Mouse would frown.
If I was coming to do this job This what I would do.
Find a way to lift the AC up a little and leave it more or less in place.
Disconnect the deck from the 2x8 in the ground and the outer post, grab a few friends and drag it back out of the way.
Dig out the trench along the house and repair or install the drain that is needed there. Bolt a treated 4x6 to the concrete wall at the 1/4" above the level of the 2x8 is now, back fill this only with 3/4 grushed gravel almost to the level of the 2x8. Add another drain in the center of the deck area and reshape the soil so the drain is at the lowest of that area cover that area with 6 mil poly and 1" of the same gravel
I would leave the 2x8 in place to hold the dirt back but it will rot over time so I would just cover it with the poly so rot dosn't get to the other wood.
Get your friends back to set the deck back in place and it will sit on the 4x6 at the the house, bolt it back onto the post on the outer end but then add another 2x8 to the ouside to make that strong enough and add galvinized hangers there for the joists if they are not there now.

I think I follow all of that and I agree that's probably the best I can do without tearing it all out and starting over. When you say 'add another 2x8 to the outside', are you referring to the 2x8 that faces the patio? Bolt a second one to that?

Another idea that's sounding pretty good right now is to tear everything out and just continue the paver patio all the way up to the house. Although, that would leave me with needing a couple steps up to the door, which I'm not a fan of.

Yes the out side should have been a double or there should have been a double under the joists but the way it is, the joist should be in hangers that are rated for treated lumber. Changing to pavers might be a good idea, but there is a lot more prep work, removing soil, replacing it with gravel and compacting. I like a raised deck my self, I find stairs down to deck makes it feel less like it's part of the house and tends to get used less.

I put the existing patio in myself, and in fact, that may have been the first thing I posted about on here several years ago. I used a shovel and wheel barrow to remove 8" of soil from the entire area and then the same to put the 6" of gravel in it's place. I told myself I'd never do that much work myself again. Work aside, I agree that stairs from a patio directly to the door is very undesirable.

I'll add the 2x8 to my list of lumber to order and pick up some joist hangers and all the drainage material that I need. Nothing is ever easy....

You've got some good info here but one thing that wasn't mentioned, except by you, was to change the deck type to a sold surface.
You mentioned putting plastic down under the deck but as you correctly noted there would be holes in that when you relayed the deck.
An option is to put a solid plywood deck down and cover it with a vinyl membrane. This would give you the full drainage away from the house that you want. Not sure if you would want the look of a solid deck surface but it is easy to maintain too. Check out this website: http://www.duradek.com/vinyl-decking/
Disclaimer: I have no connection or financial interest in this product.

Dave Mason