stiffest building board

[sm_jamieson]

What do folks think is the "stiffest" building board, or composite of 2 building boards, to have max thickness 25mm ? Stiffness being a measure of least deflection against a given force on an unsupported area of the board. In other words, the board with which you could build a partition wall using the least amount of studs and still have it stable enough to take tiles. It must also be strong enough to support lightweight shelves etc. Ideas: 25mm MDF, 2 sheets of cement board glued together, fermacell, plywood + cement board. Etcetera. Cheers, Simon.

[Phil]

25mm marine ply. The price will make your eyes water though.

[meow2222]

1" fibre reinforced cement sheet, undoubtedly. You'd have to pour it yourself though. Ply is tough stuff, reckon an inch of that would be tougher than any of ther others, but 1" ply is pricey. 2x half inch sheets of anything wont be nearly as rigid as a solid 1" sheet. If you need to use 2x half inches, gluing them together all over their faces would help.

I worked out the thinnest partition wall with so-so performance a while ago, but I cant quite remember what it was. Probably 3/4" ply faced with thin PB on each side.

NT

[sm_jamieson]

Do you reckon you could create 1" fibre-reinforced cement board by rendering it up in layers onto a substrate, to have the same final effect ?

Simon.

[meow2222]

You could do that of course, but it wouldnt be as strong as cast-in-one fibre reinforced board. If you want to make it in situ, maybe make a mould, poly line it and pour. Thin plaster skim is all thats needed (airbubbbles, bending of mould)

Casting 2' wide 8' high 1" sheet is not hard if youve got a flat 8' sheet to do it on.

NT

[sm_jamieson]

What cement mix and what fibres would you use ? I'd try a sample and test it for stiffness ! Cheers, Simon.

[meow2222]

3:1 is the strongest mix that doesnt microcrack during setting. 5% alkali resistant chopped glass fibre is one reinforcement. Asbestos fibre is frowned on these days.

NT

[dg]

The stiffness, and adequacy of a wall does not rely solely on the boards, but will depend on the timber studs and bracings. The studs control other movement of the boards, not just their flexing

I can't see why you would want to construct a wall with fewer studs and thicker boards. It will be pointless and potentially more expensive to construct.

dg

[Chris Bacon]

It's more than frowned on, it's illegal in new stuff. Polypropylene is widely used.

[meow2222]

Use tough boards and you can make it studless

NT

[<me9]

Gyproc laminated partitions (I can't find them anymore on their wibble) consisted of a 25mm perimeter frame with a 12.5mm plasterboard skin, and a core of gyproc plank (19mm plasterboard) They were bonded together with bonding compound (dot & dab stuff) (applied with a dustpan brush) in vertical strips about 400mm apart. I installed some about 15 years ago where there was limited space, and I've had no complaints. They need timber strips inserted wherever you need to apply heavy loads, like cisterns, and kitchen units, in order to take the loads Light loads just drill and plug as per plasterboard, but /dont/ use screws longer than 50mm, or you will be able to hang your coat on the other end.

[sm_jamieson]

They are now calling it Gyproc SolidWall. It looks like this idea is the way to go. Boards laminated and glued across their whole surfaces will probably give me the stiffness required (no funny comments !) Simon.