Replacing chipboard with plywood, but what kind?

[peterg792]

I'm wanting to replace bedroom 21mm chipboard floorboards (over joists) with plywood (and carpet on top).

But the supplier is offering four types:
- Shuttering plywood
- Exterior plywood
- Marine plywood
- Finish spruce plywood

Some are labelled as ok for "structural purposes" but not others. Is that relevant when used as floor boards? Should I just go for cheapest?

And is it worth paying extra for the 25mm if wanting to reduce creaking?

 

[Burnerman]

Any plywood is stronger than chipboard (not that there's anything desperately wrong with chipboard, so long as it's kept dry)......
If creaking is an issue, make sure it's screwed down well with 50 x 5 screws.
John

 

[JohnD]

shuttering ply is very rough. Marine is expensive, though you might consider it in a bathroom, and it has a good finish on (at least) one side.

Spruce ply is probably the structural one, likely to be T&G and available in about 2400x600mm sizes, which you can carry (2400x1200 is of course twice as heavy and awkward)

I found the spruce to be too rough where exposed, and used 18mm hardwood-faced WBP which (at the time) was a good price at Wickes. The face is good enough to colour and varnish, if you want to have it exposed, and it has good water resistance for occasional spills and splashes. It probably does not have a construction rating but is likely to be better than the stuff that does.

You must put noggins under all unsupported short edges, this is especially vital if you are not using T&G.

If you are going to tile it, use 25mm ply.

 

[AronSearle]

Spruce ply, European manufactured, good quality.

Don't buy Chinese.

Don't buy Chinese.

Don't buy Chinese.

Marine plywood is for building boats, no reason to use it in a building.

 

[ree]

I guess that you want to replace 18mm or 22mm T&G chipboard flooring because there is creaking in the floor?

Are you certain its the c/board - does the floor sag or bounce or sway?

How has the c/board been fastened - at what centres - what type and size of fixings?
Do you know the joist sections and spans?
Have the c/boards been fastened on joists centres ?

Thing is, if you dont know the answers to the above questions you might end up with similar creaking.

Cheap, basic T&G ply is good enough for a sub-floor. Ignore all the ply hype.

AAMOI: ply production is ripping apart the last Asian forests thereby creating more misery for millions of vulnerable people - the poor.

 

[dazlight]

Exterior plywood but don't buy Chinese

The best about in the uk is SP101 by Hanson plywood but you don't really need that as not gluing to it

 

[mattysupra]

Here is something to think about-

Exterior plywood, what location do you think it might be designed for ?

Then lets throw in Interior plywood, again what location do you think this might be designed for ?

The confusing part is the new EN standards can label a interior product as a exterior product. The reason for this is it goes on its highest rating. So you could have a interior plywood that is labelled exterior due to it has a exterior glue bond. However the plywood is dried to a interior climate!

Hard work choosing plywood.

 

[AronSearle]

Here is something to think about-

Exterior plywood, what location do you think it might be designed for ?

Then lets throw in Interior plywood, again what location do you think this might be designed for ?

The confusing part is the new EN standards can label a interior product as a exterior product. The reason for this is it goes on its highest rating. So you could have a interior plywood that is labelled exterior due to it has a exterior glue bond. However the plywood is dried to a interior climate!

Hard work choosing plywood.

All plywood comes out the factory at about 7% moisture content, interior, exterior or whatever. The moisture content in ply hasnt anything to do with it's suitability or interior or exterior use, it is only determined by the glue bond. The end user/specifiyer has to ensure the plywood has a suitable moisture content for the use, or has enough expansion gaps.

Most good plywood uses a class 3 (WBP) bond, cheap crap chinese plywood doesnt, I think it uses spit and mud?

Some of the speciality joinery plywood (like the half mm plywoods, yes half a mm) uses melamine glue instead (normally not an exterior bond), this is because it is a white adhesive and doesnt show through thin veneers.

This is no use to the OP, but I am Mr. Pedantic.

 

[peterg792]

You must put noggins under all unsupported short edges, this is especially vital if you are not using T&G.

For the noggins must it be "treated wood"?

I've already used normal planed whitewood for 3 noggins have a few left to do.

 

[JohnD]

it doesn't have to be, because interior wood is expected to stay dry.

I like to treat all timber under a bathroom floor and under a sink, because things leak.

Untreated wood can get woodworm, as well as rot.

 

[big-all]

it doesn't have to be, because interior wood is expected to stay dry.

to be honest wood will not rot if its constantly changing in its moisture content
it can be soaking one week then drying for 2 weeks then soaking again for a week over several years and it will not rot unless it spends many weeks at around 19% moisture where wet rot sets in
in general this will only happen at ground level where moisture is excessively retained at 19%
this is why sheds and fence posts rot at ground level
and ships and timbers fully submerged last many hundreds off years in mud or water