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Masonite for concrete forms

Glenburn's picture

I've got a project that requires a 5" concrete slab with multiple, compound curves.  Normally I would use 2x6's, cut a few kerfs and bend the forms where I need to.  If I do that on this job, I'll be cutting kerfs for 2 days - not an option.


I've used 5/8" plywood in the past for gentle curves, but there are some tight ones on this project.  The next thought is to use Masonite. 


My question is what thickness of Masonite would you recommend???  I've seen it used before, but I've never had the need.  Specifically, I've seen 1/2" Masonite used to pour a 4" slab, but this pour is going to be 5", and I have some skepticism about using 1/2" Masonite to form up for a 5" thick pour.



(post #90095, reply #1 of 5)

 Hardboard siding, it comes 1/2" x 10" is primed both sides, and comes in 16" lengths. Tale it and rip it into 2-5" widths.

(post #90095, reply #2 of 5)

My local plywood shop (not a regular lumber yard) stocks bendable plywood in 4x8 sheets.

I'm sorry, I thought you wanted it done the right way.

(post #90095, reply #3 of 5)

 We find the problem with 8" lengths is that a joint always falls in the bend on compounds, that's why we opt for the 16' strips of each his own.

(post #90095, reply #4 of 5)

I second the hardboard. Used it for curved forming on an 8" slab and it worked great. That was suggested by the finishers. They use masonite (I think) on lesser curves, but use hardboard on the tighter curves.

(post #90095, reply #5 of 5)

I put my vote for curve-a-board. It is the brand name for a bendable plywood. It is two to three times more expensive per sheet, but hey, tell the architect that!

scares me, and I'm fearless

scares me, and I'm fearless