hardboarding bathroom floor - waterproofing?

[brettjbuckley]

Having hardboarded the bedroom floors before carpetting, I now want to hardboard the bathroom floor before laying lino.

I can seal the lino around the edges but know that water will still find a way in. Will this rot the hardboard? Should I perhaps varnish it?

 

[gcol]

Why don't you use exterior ply?

 

[brettjbuckley]

Exterior ply would (I presume) only come in thicknesses greater than what I have used to hardboard the reast of the upstairs floors.

 

[gcol]

Which was what thickness?

 

[gcol]

Taken from diydata:

Exterior grade plywood (WBP - Weather and Boil Proof) is specially made using a water-resistant adhesive to withstand a certain amount of moisture and can be used for outdoor constructions - sheds etc. and is sometimes used as a cladding material, particularly for insert panels under windows. WBP does require additional protection (paint or varnish) to protect the outer veneer.

Internal plywood is of a similar quality as Exterior grade but it does not use water resistant adhesive. It can be used for wall panelling, flooring and furniture.

Shuttering Ply is used in the construction industry for making shuttering boxes for containing concrete while it goes off. Although water resistance to a degree, the sides of this material are not finished with a decorative veneer and is generally not suitable for use where a quality finish is required.

Marine Plywood is made with waterproof adhesive so that it will stand immersion in water, the veneers themselves will not last forever under water so the material should still be finished with paint or varnish.

Plywood is normally available in 2440 x 1220 sheets (or subdivisions) and in thicknesses from 3 to 35 mm.

Hope this helps,
Gcol

 

[brettjbuckley]

I think that the hardboard measured only about 5mm thick - I can check as the carpets have not gone down yet.

Looking at the data you kindly posted, it does mention varnishing plywood to make it water proof. Maybe I'll have to have do an experiment with some hardboard to see if that works too!

(I would tile the blummin floor but I worry about the need for access if I get a leak...)

 

[gcol]

You can definitely get 6mm ply, and if you say the hardboard is 5mm there's no way you'd notice the difference when the final flooring is fitted.
Personally, I would shy away from using hardboard anywhere near water but that's your decision.
If you do decide to get ply then get exterior ply regardless.
Good luck,
Gcol

 

[jlflooring]

hardboard is compressed cardboard and swells when damp or wet, 4mm or 6 mm ply is easily available and is a much better option.
the thickness of ply that you use, really depends on the condition of your floorboards, take care when nailing (18mm ring shank nails at 100mm centres) trying to avoid the joints in the boards as nail heads can rise leaving unsightly pimples in you floor covering

 

[Scrit]

Hardboard is normally 3.2mm (1/8 in) thick.

 

[Plumbfit]

6mm ply is what you need end of