Flooring a loft

[pinnerite]

From around the beginning of February, Mrs P and I will be moving into a bungalow that is in need of lot of work. I do not yet know how old it is but I am guessing from between mid-60s to early 70s.

The loft has glass-fibre insulation and is only partialy boarded. I intend extend the boarding. I boarded my current one with bits of chipboard let over from work done years ago. Well that was 5/8" board.

Now (soon) I shall need to buy new. It looks as though 18 x 600 x 2400 is the default today. The thing is I always aligned board edges along the centre of the joists. So that would require joists at 600mm.

My house wasn't completed until May 1972 and its joists are at

16" (406mm) centres. The "new" bungalow may be the same age. Should I be concerned if I intend to lay them at right angles to the joists?

TIA

[Tim Lamb]

In message <rnk94u$ffh$ [e-mail], pinnerite [e-mail] writes

No. I use polyurethane glue to bond the joints but you might need to consider access for moving/re-wiring light fittings etc.

Might be good to top up the insulation while you are there. I prefer Rockwool. Much less irritating for a similar performance.

The electricians will be along shortly worrying about power cables buried in insulation:-)

[Andrew]

Above the new 'flooring', or squeezed into the 4inch gap under the flooring ? :-).

Wickes sell special extension supports that lift the boarding up so that the requisite 300mm of insulation is possible. I made my own from inch thick plywood, cut into 300 mm long by 100 wide strips, glued and bolted vertically to the horozontal bars of the trusses and with 50x50 slot cut into the top end allowing a 3.6 metre length of 47x47 timber to be carried from side to side, spaced 600 mm apart and fitted the loft boards to those new rails.

[Theo]

You can get 'loft' boards, which are handy if access is tight, but doesn't address your immediate problem:

I think traditionally you lay the boards at right angles to the joists, so your 2400mm covers 6x 400mm-spaced joists. The joins are therefore at joists where they can be screwed down.

As mentioned, it's worth thinking about putting in some extra timber to raise the level and bump up the insulation while you're there.

Theo

[John Rumm]

You would normally run the long axis of the boards perpendicular to the joists. So you would only potentially need to trim an end of a board if the joist spacing is out. The board to board joins have the T&G profile and so don't need extra support.

(you can make them stronger still if you glue them, but that is usually overkill).

[Andy Burns]

Stagger the joins, but a 1/4" tongue of weetabix doesn't have much strength, so only tread where you can see screws into the joists unless you're slimmer of the month ...

[Dave Liquorice]

True but the T&G on weetabix is more like an inch and half with quite on offset between sides and the toungue/groove tapered.

[Andy Burns]

My loft boards are 3/4" (green flooring chipboard is 22m or occasionally

38mm).

[Tricky Dicky]

Because the pitch of our roof trusses is a mere 22deg there is no part of our loft that you can stand up in. However, to enable me to crawl easily about the loft to do wiring I boarded the central portion so that I could easily crawl without getting tangled with the rock wool. I simply fastened 3 X 2s to the side of the trusses at 300mm above ceiling height and used chipboard loft boards as the floor. It did mean shortening every one of them and losing about 300mm each time also not helped by the uneven spacing of the trusses. It did reduce head room considerably with me just about able to kneel in the very centre but it made subsequent work so easy. Once we complete work in the loft which will involve dropping a couple of cables into the bathroom and providing a ventilation system for the bathroom I have no intention of using the loft.

Richard

[Brian Gaff (Sofa]

My loft now only partly boarded has the insulation over the boarding as it has to be a certain thickness and many houses simply do not have that space unless the joists are mega thick!

Brian

[Dave Liquorice]

Er, so? You can clearly see the T&G that is much more than 1/4", maybe nearer an inch on those boards, and the taper.

[Andy Burns]

How do you get a 1" thick tongue on a 3/4" thick board?

[Max Demian]

Make the extra insulation polyurethane foam and provide extra sleeping space.

[Dave Liquorice]

>> 18mm-3-pack_p404607>

Ah, I see. 1" long, if you like. Less a easy to flex and spreads the load.

[John Rumm]

Do you take similar care walking over a floor in a modern house? Because the same arrangement of floor boards exists there.

Remember you are talking about a 2' wide board adjacent and interlocked with another, spanning one joist space - so there is no reason for it to give at the edge.

[Andy Burns]

Chip floorboards are 22m or 38mm though, compared to 18mm for loftboards.

I have certainly managed to crack the odd tongue off my loftboards

[The Natural Philosopher]

18mm is also ok for floors

[Tim Lamb]

ISTR 22mm is required for ground floor.

>

[Andrew]

My 1976 house has trusses and a 37 degree roof pitch, but I still managed to get full size 8x2 t&g 18mm flooring chipboard through the loft hatch.

It's a lot stronger than those 'weetabix' loft panels that B&Q sell.

[Andrew]

When the supporting joists are spaced at 450mm. New houses these days have a 600mm spacing so they use 22mm chipboard flooring.