Hearth Lower Tray

[bruced]

I have a couple of questions before I begin assembly on the hearth form. Can anyone tell me if there is a standard method that is used to attach the 2x4's for the bottom tray? I don't see any problem with supporting the tray, but I want to make the box sturdy. I also wondered how it is disassembled after the concrete is set. It seems that it would be difficult to get it out from the inside, or I guess it could just be cut and pulled out? I plan to use Hardibacker, so I only need to remove the form.
Thanks from a construction novice.
Bruce

[SteveP]

If you are talking about the bottom form for your heart layer, then you can precut the plywood into two pieces that can be easily pulled out from under the hearth. You can join the seam with masking tape which will prevent any slurry from dripping out. The 2x4s can be screwed together at the ends. I put strapping completely around the form so that the sides would not bow out. If I didn't answer your question, then review the build photos from many of the builders; I'm sure you will be able to find your answers there.

[bruced]

Thank you Steve. I didn't think to use tape to seal the edges. I actually searched through forum photos and descriptions and could not find any that showed how they attached the inside frame walls. At Home Depot I spotted some 1.5" corner brackets with perfectly sized holes for wood screws. That should take care of it, and will also be easy to disassemble after the floor is set.

[wlively]

If you are using Hardibacker and planning to leave it in, you don't need a form. You can just cut 3 2x4s to stretch the length of the form and then support each spanning 2x4 with 3 2x4 legs. When cured, simply knock out each leg and remove the 2x4s.

[bruced]

Thanks Wade. Once you said that it seemed it should have been obvious to me. Since the Hardibacker will be supported by the block stand, why would I need a frame? I laid the sheets across last night to check, and I can see that it will be very solid once the 2x4s are in place. I will try to salvage as many legs as possible from the boards I prematurely cut.

[bruced]

Any advice for holding the support legs in place? It seems they could topple before the weight from the concrete takes over to snug them up. If I raise them enough to be firm, it tends to lift the Hardibacker.

[fxpose]

Originally Posted by bruced

Any advice for holding the support legs in place? It seems they could topple before the weight from the concrete takes over to snug them up. If I raise them enough to be firm, it tends to lift the Hardibacker.

The easiest way to hold them in place is to stack cement blocks up against them.

[GianniFocaccia]

I placed three 2x4's across the width of my support slab form and supported them with 4x4" posts I had laying around. I just cut them to fit and they remained in place nicely. Turns out the weight of my pour caused the bottom of the form to sag ever so slightly (almost un-noticeable). If I ever do this again I will place a row ofsupport posts right down the middle of the form.

[Neil2]

"Any advice for holding the support legs in place?"


Glue gun.

[ckdickerson]

The only support legs I used were in the center of the form to prevent sagging. I used tapcon concrete anchors to fasten 2x4's around the inside perimeter of my stand and layed prywood on that. It was very solid and easy. The tapcons even came with a masonry bit.