Behind the Build: Basement Concrete Floor
An overview of the Scott Simpson Design + Build process of creating a basement concrete floor for a new construction custom home – the make-up of concrete, how a screed machine and hand finishing while on kneeboards make it smooth as it sets.
Alright Tom Kenny here at Scott Simpson Design + Build. Today we are pouring the concrete floor here at 1020 Butternut. They’re rolling the concrete out of the truck, down the chute, and the guys are using concrete rakes to kind of spread it. They put it around the perimeter where there’s a red grade line so the guys can see what’s going on. There’s a laser set up, and when he holds it up to the exact right height it’ll begin to beep. That’s how they can figure out what the grade looks like.
Concrete is made up of four basic things: fine aggregate which is sand; coarse aggregate, which are rocks; cement and water. We’ve also added this really fine fiber to the concrete. You know, in the old days when they did plaster, they added horse hair to the plaster to make the plaster really strong and keep from cracking, It’s exactly the same principle because as the water actually dissipates and evaporates, the concrete volume gets smaller and tends to crack, so these fibers are designed to hold it together.
The blue paper, which has been taped down, is the vapor barrier that keeps water that’s below the actual slab from seeping up through the concrete. The concrete’s curing right now so it’s a bit of a race against time. If they take too long, it’ll actually cure up so fast that they can’t finish and it’ll stay rough. The boxes that are inside of the concrete slab right now are forms that are keeping the concrete out because we’re going to set steel columns there.
This concrete floor is designed to carry 4,000 pounds per square foot, which means that this little 1,400 square foot floor is designed to carry 5.8 million pounds of load if we ever need it.
So, he’s working the power screed in the back. It’s like a weed whacker with a long aluminum screed on it and what they’re trying to do is flatten the concrete.
The fun part for the homeowner is they actually got to design what goes into this basement. Over there you can see the plumbing for what’s going to be a basement bar. Right in this region there’s going to be a small powder room with a little shower. The owners’ designed a movie theater section. There’s an area for a future wine cellar.
When we’re done we’re going to have a finished nine-foot ceiling, so when you go down into their basement you’re not going to be feeling like you’re in a subterranean space.
They’ll work their way out the window, they’ll pull their knee boards up outside the window, reach down from the window, finishing screeding it, and then they’re done.