The beginning of framing: How I used concrete to prep my walls for wood studs!

In the beginning I thought the framing would be one of the easiest parts in the building process [complexity wise], but I was certainly wrong. Maybe it's just too damn hot outside.

On the bright side; so long as you're creative, there's a way!

The first thing I discovered with the inside framing is that the metal studs on the inside are built into an inch deep trough, and comes up above the wood flooring about a half inch. That's a problem for traditional 2x4 framing as I needed a level surface to place the wood studs on, and I didn't want to cut or bend the metal lip since it seems to be the base plate for the metal studs and is necessary to the structural integrity. Plus I doubted I could get it flat enough had I bent it.

Originally I planned to cut some wood pieces [1inch x 1inch] and place them into the inside trough, and nail some 1/2inch on the outside to level them out. Unfortunately, I couldn't find wood the size I needed and I didn't have a way to rip the wood to the width I needed. So I got creative.

I thought about using leveling compound and pouring it into the trough, but when I looked more into that I found out an inch thick pour is a bit much for leveling compound. [And boy is it expensive.]
Spray in foam might work, but depending on the type of foam it's prone to shrinking over time.
So how about concrete?
I know a lot of people worry about weight for their build, but the GVWR for my truck is about 11,000lbs and I figured it's worth the added weight. [I used about 1 1/2 bags, so about 70lbs worth.]

I bought this brand of concrete because it allowed me to dry pour the concrete and then soak it, which was very helpful considering I don't have water on site where i'm working. Fast setting indeed; since it was so hot outside and the metal of the truck was hot, it set almost immediately. Plus it was only $4 for a 50lbs bag at Home Depot

• I started off just filling the troughs to the top of the lip so I could get the concrete into all the small crevices:

• Originally I mixed it in a bucket thinking I could pour it in more quickly, but I ended up pouring it in dry and then soaking it. Worked way better! There were a lot of rocks in the mix, but the top ones can be brushed off when it's dry - leaving a level surface. Once all that set, I started to saw some of those 2x4s I had left over after I took down the shelving that was inside the truck when I bought it:

Who needs a chop saw when you've got stubbornness and arms of steel amiright?

• I screwed those to the wood floor and made sure it's level.

Now we're ready! 

 

Then I used a water bottle to pour in the water, leveling it immediately. It sets quickly!

The corner of the walls in the back are curved, making it a bit more difficult to frame had I used wood instead. Luckily the concrete filled up the space perfectly.

 

I was thinking of adding wood shims on top of the concrete to give me something to screw the back of the 2 x 4s for the walls into, but after it dried a bit I double checked to see if it was level and found a 2 x 4 stud fits in there perfectly and level. I think i'll be toe-nailing the studs to the floor 2x4s in the front of the stud, and that should work great.
[But not before I add my waterproof barrier to the walls! I'd rather not worry about condensation from the metal rotting my insulation and studs later on, which seems to be a big (reasonable) concern.] 

 

It turned out there must have been small holes inside the troughs I didn't see, as I saw a small amount of water drip out to the ground outside. That was a surprise bonus using concrete for this, as it will act as extra insulation and cannot rot. The vibration of the vehicle might crack the concrete over time, but the walls won't be weight bearing so that shouldn't be a problem.

All in all, it's been a lot of work just to get it prepped for the wall and floor framing. 
But as the saying goes: They never said life was easy. They just said it would be worth it.

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If you found this interesting or have any questions, please leave a comment or message. Thank you for reading and I'll be back with updates soon!

Sincerely,

Kelli