It must be that time of year.
The snow is melting, the site is unfrozen and it’s time to start setting boxes.
I’m getting the same question in my email over and over again right now. I’m also seeing the same questions asked in other places on the web, from “DIY to Specialty” blogs.
So, let’s address a question about HOW you attach the ISBU to the ground;
Are you a Ninja? I’m just wondering because… oh, never mind.
(Editor’s note: No, I’m not a ninja, wise guy. I’m “The Man Of Steel.” Corten Steel. )
You’re constantly talking about putting ISBUs on pilings. You’ve even explained in great detail how to make them out of Sonotube casings.
But what if you want to just put the ISBUs on a poured concrete slab?
You know… not all of us want our ISBUs up in the air.
I want to just pour a slab and then possibly even embed some twistlock bases into them and then drop the boxes onto it. I do know how thick the slab needs to be, as I hired an engineer to calculate it for me, so it’s all good.
If I set the boxes at a distance, say about 20 feet apart, I can get a pretty good size house for cheap. I know that it’s true, you say it over and over again.
Man, you do tend to repeat yourself. 😉
In fact, after I visited an ISBU Pool House you built in Fort Myers, we decided that we’re going to build a house like the “Shindig House” you showed on your blog. It’s exactly what I have in mind.
(Editors note: He’s talking about an ISBU Pool Cabana /Guest House we built a few years back in somebody’s back yard, in South Florida. Essentially, it’s a pair of 20′ ISBUs with a common center section, covered by SIPs and SSMR. I think it even made a few magazines.)
Here’s what I don’t get;
The guy who wants to pour my slab keeps telling me that we have to grade the area and then cover it with plastic before we add sand to pour the concrete on top of.
Won’t the plastic keep the slab from drying?
Then after he gets done, we can’t use the slab for at least a week. In fact, he says he needs to send somebody by to water it.
I’m trying to work as fast as I can. Is he right about this? Or is he just padding his bill?
Your concrete guy is absolutely right.
Grading the site keeps stuff from puncturing the plastic he’s going to line your slab form with. You want to start with a smooth, clean surface and you want your slab thickness to be consistent.
(You ARE dropping some rebar into it, right?)
You WANT to keep that slab “wet” for as long as you can (within reason). The plastic (usually 10mm sheets of visqueen or something similar) will help that happen.
This may confuse you even more, but then WET sand is usually added on top of the plastic, trapping in even MORE moisture.
THEN… you shoot your slab.
The idea is to keep the concrete wet to help it “cure” slowly and evenly. The end result is that this method produces a MUCH stronger slab.
When we shoot slabs for ISBU homes (or any other kind of homes or structures, for that matter) , I have people “water” them at least twice a day, (and sometimes even more depending on geographic location), just to keep things going the right direction. THAT is why he wants to revisit your slab. He doesn’t want your ISBUs to break it.
TIP: Depending on the end purpose of that slab, sometimes I’ll even shoot some sealant over it, to further slow down the drying process.
And you MUST wait at LEAST a week before you start playing on that slab. Two weeks is even better. If I can wait a month, I will. The last thing you want to do is damage it by banging on it or loading it up, too soon.
A 40′ ISBU weighs about 8,000 pounds. A brittle (uncured) slab will cause you nothing but grief, once you set that big hunk of Corten Steel down onto it. Trust me on this.
So stop your crying and write that check.
BTW: You owe your concrete guy a frosty cold one. He’s looking out for you.