Living in the wet upper Midwest, rain and drainage causes some problems. Fortunately I've tried to learn a bit about how to manage runoff but I do have a question. Last week I finally had a new driveway poured. 4" over compacted sand and crushed gravel. Rebar of course. Now that the forms are removed I'll need to backfill. But as the previous driveway broke up due to water getting beneath it, I'm wondering what to use as backfill. Nearly everyone says a sand/ gravel mix works for drainage. But our soil here is clay. I was thinking of using the fill / clay graded away from the driveway pads to extend the water runoff. OR, should I fill the first inch of two with sand/gravel then cap with the clay fill? I do need to look closer at the overall water drainage but wanted some input to prolong the driveway life.
Sand/gravel is different than crushed limestone and gravel (2b modified). The modified is pretty impervious to water, as would a good clay soil. You want to manage the run off such that it is directed away. You want to use dense fill like clay or the modified and pack it well.
I would throw down some Geofabric, over the clay, then backfill with 2b top dress with 1b if you want a softer look.
+1 only thing i would add is some drainage pipe so that the water moving into/ through the 2b has a clear path "away" from your driveway investment. best of luck
If I understand you correctly, lay down the clay fill first, Geofabric, then the 2b gravel. Would I lay down the clay as a 'ramp' against the thickness of the cement pad, so it diverts water away from it? Would this create anything weird with the expansive quality of clay? My second thought was to use the clay in a similar way, but after filling the gaps in the current gravel with sand etc, to avoid settling from what's already there.
Wouldn't this promote water running along the side of the slab? I would think you would want to back fill along the side with some type of impervious fill, like 2b modified or straight up clay. A porous fill could promote water wanting to get under the slab again. Sent from my iPhone using Tapatalk
Good Drainage /run off = proper grading and slope. Expansive quality of clay = movement during freeze thaw cycles. I would put the fabric down just to keep the clay from swallowing the stone.
So, to reiterate: Lay down the clay fill first, Geofabric, then the 2b gravel or similar. Would I lay down the clay as a 'ramp' against the thickness of the cement pad, so it diverts water away from it? Would this create any concerns with the expansive quality of clay?
We have a bit of rain over here in UK. You don't say how long the drive is or what your budget is. I'd look at a French drain, lay 3 or 4" perforated pipe (perfs up) over some clay, than back fill with coarse gravel, say 20/50 (that's the mm size). The bigger the gravel size the faster the water drains through to get picked up by the perf, which needs to be below the base of your drive. You just need to arrange grading so it all runs off to be someone else's problem.
The other advantage to this is that it will collect driveway runoff and divert it away from the yard to keep nasties (oil, grease, fuel, salt, soap, etc.) from permeating the ground on either side.
Set up a swail to bleed the runoff water off the back of the lot as well as down parallel to the driveway. I have enough angle to install a French drain though this is the 'open' version of it. Sand backfill against the driveway slabs to 2" below driveway plane. Fill 1-1 1/2 " with 21aa gravel then top with heavy clay fill for runoff. Set grade 12" beyond edge of driveway, swail line.
Thinking it will work. Dingbat next door neighbor has a garden 4' from the lot line. No problem with the garden itself but she's got a French drain lying 1/2 above her grade. Not sure how she thinks that 'should' work. Since I've extended the runoff with the clay cap into the swale I'm guessing I'll have little to no problem with my backfill washing out.