Old timer told me to wet the subgrade before pouring

Guy named Rick with 30 years in the biz swore up and down we needed to hose down the dirt before the pour on a driveway job in Austin last month. I thought it was a waste of time and water, but he insisted. Ended up with way less cracking and the slab held moisture better during the cure. Has anyone else run into old school tricks that actually work better than the modern way?

3 comments

3 Comments

the_lucas2mo ago

You ever see a guy just dump water on a hot slab and it turns into a steam bath? That happened to me on a patio pour in July. I figured the ground was dry enough, but after we poured, the bottom of the slab sucked the moisture out way too fast. Ended up with hairline cracks along the edges. Next time I wet the subgrade down real good, let it soak in, then poured. Slab came out smooth, no cracks. Sometimes the old timers know what they're talking about, even if it feels like extra work.

rodriguez.diana2mo ago

I get what you're saying but I had the opposite experience. Wetted my subgrade too heavy one time and ended up with a muddy mess under the slab. Took forever to get the concrete to set right and it left a rough texture on the bottom side. I think there's a fine line between damp and soaked. If it's just a light misting with a hose that's fine, but soaking it for hours like some guys do? Not for me.

terrybennett1mo ago

Rodrigo's right that too much water is a mess but the trick is timing. I've found that if you wet the subgrade the night before and let it drain overnight, it's damp not soaked by morning. That way the ground has moisture in it but it's not soupy. For a hot July pour I'll even use a sprinkler for about 20 minutes the evening before, then check it with my hand the next day. If it feels cool and damp about an inch down you're golden. The key is letting that water soak in deep, not just sitting on top. It's like watering a plant you don't just dump it and walk away you give it time to drink.