Flooring in a loft

Hi I am intending to lay some flooring in our loft, as I am fed up with hopping from joist to joist when putting things in there for storage (I know, if I threw them away there'd be no need to go up there but ...).

It's a 1930's house with joists 100 mm x 50 mm, about 4.2 metres long at 350 mm centres, lath & plaster ceilings. I don't think these will strong enough to take the load without deflecting enough to crack the ceiling underneath, even though the local Council (Building Regs office) say they are OK for the static load. So I want to strengthen the joists before laying the flooring (V313 chipboard T&G four sides). However I am not sure how to do it. I initially thought about screwing some 50 mm x 50 mm on top of the joists, then thought I should make it 50 mm x 75 mm (or even 50 mm x 100 mm) so that I can have a nice depth to upgrade the insulation. But I'll need some really long screws to get through 100 mm and bite into the joist underneath, and will probably wear out the cordless drill doing it! Anyone able to suggest some alternatives?

Also - before putting starting I intend to coat the existing joists with wood preservative, just in case condensation under the floor becomes a problem. However, I am worried that any preservative which gets on to the plaster will cause staining underneath. Anyone with any experience of doing this? The new timbers will be pre-treated.

Many thanks

LS

Reply to
LS
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I did a 1930's loft a short time ago. I didn't consider this loading to be a problem to be concerned about - if you use flooring grade chipboard panels which you buy in the DIY sheds then the load is going to be spread over a couple of joists anyway - these boards don't flex more than a very small amount which is next to immeasurable.

With regard to condensation, I think maybe thou doth worry too much :)

Loft flooring isn't generally wall-to-wall with no gaps - you just fill the roofspace with flooring board so that you can't put your foot thru the ceiling below. There are always gaps where air can circulate. Leastways, there are in the lofts that I do flooring for - I'm not being paid to provide a work of art, but to give much-needed useful storage space.

Generally speaking loft floors aren't like floors elsewhere in the house, where gaps would look very unsightly. Up in the loft all you are doing is providing floor space to stand junk on (stuff that you feel you can't throw out). You don't live up there, you aren't going to carpet the area, and no-one in their right mind is going to be critical about the small gaps here and there. And those small gaps allow air to circulate and thus eradicate any moisture issues.

PoP

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Reply to
PoP

Which is exactly how I did mine. I bought some 2.4 m bundles of 100 mm x 22 mm rough-sawn timber from B & Q Warehouse in Slough (dirt cheap), then cut lengths to straddle a couple of joists, spacing each plank by 40 mm from the next one. I initially used nails, but the plasterboard under the joists cracked in one or two places, so I continued with wood screws instead, just one each end to keep the plank in place.

Works a treat, looks neat, you can walk across no problem, or stand boxes on. Cost about £40.

MM

Reply to
Mike Mitchell

Sounds like another good solution Mike ;-)

I was thinking though about the bits that you are bound to drop between the planks and *will* vanish into the insulation ;-(

Apart from affecting the ventilation I wondered if you could lay some strong paper down first (netting might be nice but not sure you could get some cheap) ?

Funny isn't it, we go from large sheets of chipboard to T&G chipboard loft flooring, plain chipboard, T&G wooden flooring, planks side by side to planks spaced apart.

I love it when you go in someones loft and you can't tell under the dust if it's cardboard or steel on the floor!

All the best ..

T i m

Reply to
T i m

In message , PoP writes

Me neither. Ands I have similar joists. and if my ceilings are anything to go by they became cracked long ago..... But I've noticed no problem.

Indeed, I think mine are probably 3 inches deep as ISTR that I put battens on top so as to fit in the 100 mm insulation. Fixing substantial timbers to the top would be pretty expensive, and unless it went right to the ends so that the load was taken by the supports wouldn't the load just be transferred to the other joists anyway?

Well the bit that I have boarded has few gaps in, and spreads across the central area of the loft. There will be little ventilation to the central section as the insulation fills the space. Some here have advocated putting down polythene sheet between the joists as a vapour membrane. I didn't bother. I had cause to lift a bit of the floor in the winter, and saw no evidence of condensation.

Reply to
chris French

You make a habit of going in people's lofts?

Perhaps you are a tradesman though and have good reason.... ;)

PoP

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Reply to
PoP

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