I always thought a 4-inch slab was fine for a driveway, but a county code book proved me wrong

I was looking through the updated building code for Johnson County last week, and it said the minimum for a residential driveway is 5 inches of 3500 psi concrete over a compacted base. I've been pouring 4-inch slabs for years on driveways, thinking it was standard. The code book specifically noted that 4 inches is only for non-vehicular pedestrian areas. It made me realize I was setting up clients for potential cracking under heavier trucks. Has anyone else had to adjust their standard specs after checking local codes?

4 comments

4 Comments

aaron85427d ago

Yeah, the "compacted base" part is actually a huge deal too. A 5 inch slab on soft ground will still fail. I've seen guys pour to code thickness but skip proper gravel and compaction, then get callbacks when it sinks under a delivery van. The base prep is like half the battle, lol.

logan52527d ago

Wasn't there a study showing like 80% of slab failures are from bad subgrade prep?

the_leo26d ago

Honestly this happens everywhere, not just with concrete. People just do things the way they've always seen them done without checking the actual rules. Like @aaron854 said, even following the thickness code doesn't fix it if you skip the other steps. It's a good reminder to actually look stuff up instead of just guessing.

price.ben1h ago

Remember when we all thought thickness was the only thing that mattered? This thread really shows how wrong that was.

-1