Overkill? Nah, just saving headaches down the road.
That’s the truth. I once thought a 4" gravel base was enough under a garage slab on clay—looked fine for a year, then the first wet spring hit and the cracks started. Now I always overdo drainage: geotextile, minimum 8" washed stone, perforated pipe at footing level, and a proper vapor barrier. Might feel like overkill, but it’s just smart when you’re dealing with unpredictable soils. Skipping steps to save a few bucks up front usually means paying double later.
Now I always overdo drainage: geotextile, minimum 8" washed stone, perforated pipe at footing level, and a proper vapor barrier.
That’s pretty much my checklist too. I’ve seen too many “good enough” slabs buckle or heave because someone underestimated the soil or skipped the vapor barrier. Ever tried using rigid foam under the slab for insulation? It’s not always necessary, but in colder climates it can make a big difference in comfort and longevity. Curious if you’ve noticed any downsides to going that route?
I went back and forth on the rigid foam under my garage slab—mainly because of the extra cost. Ended up skipping it, since our winters aren’t brutal, but I did wonder if I’d regret it. A neighbor did use foam and swears his shop stays warmer, but he also mentioned some minor settling near the edges after a couple years. Not sure if that was the foam or just his soil, though. For me, the vapor barrier and drainage seemed like the best bang for my buck.
Ended up skipping it, since our winters aren’t brutal, but I did wonder if I’d regret it.
I’ve seen that edge settling a couple times, and it’s tricky to pin down the cause. Sometimes it’s the foam compressing, but more often it’s just poor compaction or drainage at the perimeter. Did your neighbor mention what thickness foam he used? I’ve noticed 2" seems to hold up better than 1", but it’s not cheap. Vapor barrier and drainage are definitely the basics—hard to go wrong there.
- I’ve always wondered if the extra inch of foam is worth the price, but I guess it depends on how much freeze-thaw you get.
- Perimeter drainage is one of those things people skip, then regret later when the edge starts to sink or crack.
- I did 2" foam on my last slab, but only because I got a deal on leftovers from a commercial job. Otherwise, yeah, it’s pricey.
- Did you end up compacting the sub-base yourself or rent a plate compactor? I’ve seen folks try to skip that step and it never ends well...