How to thicken 9mm mdf cupboard doors

[Barry_Convex]

Hi, some advice would be brilliant.

I'm panelling a nook for a client with 9mm butt and bead cladding made from green MDF.
They want a shelf recess turning into a cupboard with the same material.

The question is how to thicken this stuff to make it thicker and more able to take hinge screws?

I tried laminating with 5mm ply over the weekend but it has banana'd by an inch (different materials/expansion? Under floor heating?)

Do I just need a better flat surface than the (unbeknown to me, heated) floor?
Should I think of framing the back with 15mm battens instead?

Dunno, what's the best approach?

Many thanks.

[dewaltdisney]

Glue same to same. Another piece of 9mm glued on makes up and 18mm thickness which is ideal. Use a non water glue to avoid any bending. If you have a router you could make your own panels up using a thicker board. The cutter is the biggest expense though.

DWD

[big-all]

cut and store in the same room for several days to acclimatize to reduce the expansion risk to a minimum
it may be easier to remake in 12mm mdf

[Barry_Convex]

Hmmm, thought you might say that. Guess I'm off to buy more panels then...

Thanks.