Construction Site Question

[ChrisLBren]

Hey Group,

I am currently building a 48 inch long by 16 inch wide build board for LGV.  Both the 3/4 inch birch ply and 3/4 inch MDF are not dead flat.  I am hoping that by screwing either board into 3 inch by 1 inch battens on the underside it will remain flat.  Does one board over the other have an advantage as far as no future warpage ?  Also it is my understanding that sinking screws into MDF may not be the best idea - I could be wrong here.

Thanks

[allanyed]

2 hours ago, ChrisLBren said:

I am hoping that by screwing either board into 3 inch by 1 inch battens on the underside it will remain flat. 

My main two boards do have a frame work of 1X2 around the periphery plus two in the center running in the short direction.  No warpage and they are both over 10 years old.   One has 3/4" plywood for the top and the other pressed composite "wood"   One has two grooves running length wise in which metal channels are screwed to allow use of an overhead bridge that I learned to make from member and author Ed Tosti.   

Allan

[Charles Green]

Look for a source of ply and MDF that stores their inventory flat.  Buy and start with new flat pieces.  If no one in your area stores their sheet stock flat, ask permission to cherry-pick from what is available.

Flattening warped sheet with battens, sheet that will be the foundation of your build, should be a distant 2nd choice.

Even when starting with flat sheet stock, using battens to keep them flat is a good idea.

 

Screws into MDF is not a good idea for commercial or residential building construction.  I will hazard a guess it is against code.  Screws through MDF, into a solid substrate, is acceptable.

[Paul Le Wol]

Hey Chris, you could buy a 4’ x 4’ sheet of half inch ply, cut it into 16” x 48” pieces and glue the pieces together so that the wows cancel each other out. I’ve had pretty good luck with that in the past. Last year I picked up what Home Depot calls a project panel. They are made of 3/4 inch 1” x 2” pieces glued together. I bought one that is 12” x 36” and it is still straight. Here’s a few pictures of it

 

 

 

[kurtvd19]

35 minutes ago, Charles Green said:

Screws into MDF is not a good idea for commercial or residential building construction.  I will hazard a guess it is against code.  Screws through MDF, into a solid substrate, is acceptable.

Absolutely against the National Building Code - Residential and Commercial.

[Roger Pellett]

Chris,

 

Wood, and wood products are not stable.  They expand and contract with changes in humidity.  Craftsmen, working with veneer, have learned to “balance” their work by adding a second veneer to the bottom of their work.  Sellers of veneer sell cheap veneers especially for this purpose.

 

We can use this same technique to our advantage when constructing a building board.  The attached photo shows a small building board that I recently built for an upcoming project.  The top surface is balance by the piece on the bottom.

 

Roger

 

 

 

 

 

 

Edited October 21, 2022 by Roger Pellett