Frame for bottom tray

[jimkramer]

The instructions say to make the frame for the bottom tray out of 2x4 turned on it's side. From the photos, it looks like that means resting on the widest (3.5") side. Is that right? Okay, dumb question: how do you nail them together at the ends? 4" nails? 45 degree cuts nailed near the corners?

[ggoose]

Bottom tray...?

[dmun]

it looks like that means resting on the widest (3.5") side. Is that right?

Yes, that's right: you want to end up with a 3.5" thick support slab.

how do you nail them together at the ends? 4" nails? 45 degree cuts nailed near the corners?

I'd use butt joints, no need to get fancy. If you have 3" drywall screws, use those, less likely to pull out under the weight of the concrete, and easier to get out when you want to break down the forms, but nails will do fine if you don't.

[Tman1]

Dmun,

I think 'resting on the widest (3.5") side' is incorrect. (Hence the question about 4" screws). It needs to be resting on the 1.5" edge so it is standing giving a 3.5" depth (allowing for your suggestion of 3" screws).