Shed floor - about to put the T&G down

[subhuman]

About to put the T&G down for my shed/cabin floor.

Base is 6x2 timber. Polystyrene sheets wedged in between to give a bit of insulation, stop any draughts.

During the construction phase I laid a sheet of black DPM over the top, mostly to keep the rain off.

Should I remove this before laying the T&G, if I leave it will it cause problems? (thinking condensation maybe?)

Also - T&G is untreated. Worth giving it a coat or two of wood preserver on the underside before nailing down? Or a waste of expensive preserver?

Cheers

 

[big-all]

you need to get air to the timbers to allow moisture to escape

is your flooring at least 20mm thick??
i assume its softwood planks ??

you would not be wasting preservative on exposed timber

 

[subhuman]

Righto. Will take the DPM up then!

Boards are 18mmx90mm T&G. Not expecting too much bounce as the joists are at 350ish centres.

Worth going to the effort of preservative on the underside of the boards? They're not exposed to the elements as such. They are in contact with the tanalised joists though of course. Top will be a hard varnish, possibly carpet on top (it's one of those shed/log cabin things)

 

[big-all]

i assume your joists are not in contact with the ground

 

[subhuman]

They sit on concrete blocks about 6inch away from ground. DPM in between block and timber.

 

[big-all]

excellent good news

 

[JohnD]

I always use Cuprinol top, bottom, edges and ends, on outside timber, even if out of the rain, applied before fixing so you can protect ends and cut edges. Otherwise, it will be very prone to worm, and dampness will encourage rot.

Hard varnish can crack due to movement as humidity changes. You might consider a Decking stain or oil instead.

I have recently started using decking timber for outside work, as it is pre-treated and non-slip.

 

[big-all]

i always set the end off the floor joists 1" in an 1" clear on the sides
i also overlap the sides 2 to 3" to cover the floor and and give some protection to the joist ends
you need to make sure you have at least 2" clearance between the ground and the sides