Hi,
I have a question about patio drainage and opinions about constructing both the patio and drainage.
In the back of my house I removed a patio – basically pavers laid on top of soil. 10 feet in back of the house is a stone/cement retaining wall about 4’ high. This is the area where I need to create a new patio; so the patio will be 10’ wide by 40’ long. About 15’ of the patio will extend past the house (if you were looking at the site from the air.)
I plan to excavate down 12” and rebuild with gravel, stone dust, etc. My question (a bit long winded) : once I excavate down 12” I will compact the soil. One contractor told me he would put down a layer of EPDM across the back and drain the water toward the side of the patio that extends past the house and then use a French drain to move the water from the back of the house, along the side to the front. The EPDM would be used to catch the water that rains on the patio. Does the EPDM solution sound like the right way to go? It seems like a lot of water that the French drain along the side of the house will have to handle. I’m worried about redirecting the water to another side of the house and having it find it’s way into the house on that side. However, I am trying to figure out how to catch and moved the water that falls on the patio, works it’s way down to the compacted soil – I don’t want to just move it to the side of the house and create a problem with drainage over there.
I live in Boston MA.
I plan on doing this work myself……….I can attach pictures if it would be easier to see than conceptualize….
Any thoughts are appreciated!
Joe
Replies
Patio drainage
Start by looking at the whole site, see which way the ground already slopes, and use this to get rid of the rain.
There are two ways to deal with this, the first is to lay the patio with a slight downwards slope not more than 3 degrees, this will shed the water, the patio will still appear flat/level.
If you are expecting a lot of rain, then lay as above, then have two inch gaps between the slabs and fill the gaps with pea shingle, this will aid the run off.
There is no need for a French drain as long as there is somewhere for the water to go once it is off the patio.
I have a similar situation and I found a possible solution here on FH that uses the EPDM as a sort of foundation gutter to catch rain water and direct it away from the foundation. Sounds like a sound plan and is alot less labor intensive than a full excavation of the foundation and installing perimeter drains.
My rear yard is basically level and perhaps even slopes a bit toward the basement foundation walls which causes water seepage down the wall to the floor/wall intersection so my hope is that by getting the water away from the walls the problem will be solved. The house is on high ground so it's highly unlikely that the seepage is caused by a groundwater issue.
I haven't decided whether or not to go with the optional french drains at the yard edge side of the EPDM to direct the water to the side of the house. If I do I'll send it to a daylight drain down a slope.
Is that your plan or is your drain going into an underground drainage field at the side of the house. Or going into an above ground swale or retention area.
Response to jerseyjimer
Hi,
The surface of the patio is going to be partly thermal cut (2" thick) bluestone - the kind that has squared edges, not the rough edges (behind the house) and partly a deck that will be set on the stone dust at the same level as the bluestone. Deck will be PVV boards.
I haven't decided where to send the water. Either a drywell that has a pop up vent for overflow or, most likely will route the water (including drainage from the roof) to the front of the property. In the front of the property the is a very large cement retaining wall (3 feet thick and 35 feet long) that is our parking area. The retaining wall has a huge amount of gravel backfill so the contractor who told me about the epdm also said I should route the water to that area and let it drain.
One of my concerns with the epdm was that I was thinking is would be under the "bluestone" part of the patio and not the deck part, since the deck part is not directly behind the house. But then I was thinking that sending all that water toward the deck isn't getting the water far enough away from the house and it would just drain to the side of the house and foundation - that is why I was thinking a french drain......
Your comments have been helpful!
Keep 'em coming!
Joe
JJ, that EPDM plan is precisely what we do with underground houses. No perimeter drain is necessary if you extend the "umbrella" far enough from the foundation. For Passive Annual Heat Storage, we normally extend the umbrella out 20', but that is for a reason other than drainage. Some, myself included, chose to install a footing drain anyway. Never a drop exited, long since plugged.
Good luck.
Reply to VaTom
Hi,
I am planning on using thermal cut bluestone 2" thick slabs with square edges on the part behind the house and pvc decking at ground level for the part that extends away from the house.
What is PAHS?
Also, someone else mentioned to me that there is a polymer (?) product available that I can use to fill the gaps between the bluestone - supposed you brush it between the cracks, water it and it hardens nicely.
Has anyone used that before?
Thanks!
Joe
PAHS: Passive Annual Heat Storage. Puts excess summer heat into the mass (cooling the house), storing it for winter use, entirely passive. The book was published in 1983. Applicable, with design tweaks, for almost any climate and almost any architecture.
The reason I mentioned drainage speed is that many jurisdictions require slow drainage, helps prevent minimal storm systems from getting overloaded. In our small city we had that requirement for a commercial property, used pavers that were permeable, stored what the city considered a significant amount of runoff for slow release.
My nephew had a dry well installed that fixed his problem, until it was full. Hard to have one too large. Best is to plan where all the runoff will go.
Your polymer I don't know, but that's a traditional application for pavers.