Loft floor strengthening, I have piccys

[blasted]

Right i have a loft space that would be ideal to bung a few bits and bobs up there. However I am not going for the full on loft conversion, i dont have the money or a suitable space to put a staircase.

I would however like to make the floor stronger and in line with the current building regulations. The money may turn up one day and as such the floor would already be done.

Attached are some pictures of the loft and the floor. The current ceiling joists are 6x2 and are overlapped in the middle above a studded wall to cover the span. The bottom purlin is 6x3 and the top purlin is 8.5x3. Both the top and bottom purlins are resting on the wall blockwork. The ceiling joist are below.

My idea was to use joist hangers off the bottom pulins, and use 8x2 to span the centre section. The floor would be on that and the purlins into the brickwork would carry the load of the floor.

Any other ideas or suggestions chaps?

[esdubu]

Don't use joist hangers on your purlins, they're only designed to carry the load of your roof, not a floor. Including timber and flooring a floor can easily weigh a couple of tonnes. Joist hangers ideally need to be on to the wall plate (internal brick course) It helps if you've got load bearing walls internal to your house as well to help spread the load.

Try reading up and asking a few questions on this forum http://www.ebuild.co.uk/forums/messa...tml?1217926458

I found it invaluable for advice about construction of my floor and tolerances of materials.

[blasted]

Thanks for that,

however I would be unsure as to how i would run bigger joists from wallplate to wallplate, as there is onyl 6 inches under the exisiting bottom purlin.

How about bolting something like 8x2 to the 6x2 but only in the middle section?

[esdubu]

Not too sure to be honest, i'm no expert. Your best bet is try the forum i've linked to. There are a lot of tradesmen and people in the know on there.

[RichardK]

Usually to take the load of the floor steel beams would be run alongside the purlins, set into the wall at each end, and joists fitted between them.

The building regs also require a certain amount of headroom, so you should check up on that too.

I think your existing ceiling joists are large enough to take flooring sheets, so I'd just get suitable grade chipboard sheets and put them down. If you do go for the full conversion later you can re-use the sheets.

It's also worth considering that the building regulations do change, and the work will need to comply with the regulations in place when the conversion is done.

[blasted]

Thanks,

having thought about it, the maximum defection is at the centre, so if i were to bolt 8x2 directly to the joists between the bottom purlins it should be more rigid. I accept that there will be more weight on the bearing ends but i feel the 6x2 may be sufficient if rigid enough.

any thoughts?

[englishrick]

Here you go...
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[blasted]

I can’t see the above image on the works computer, so I will have to wait till I get home.

But in the meantime I have been asking around, and by far the most likely scenario is to use two steel sections just inside the bottom of each binder . The span is 6m and I would need a minimum bearing of 100mm at each end. Also depending on the blocks I may need a pad stone, but I have dense blocks so I may be all right. So that I don’t have to rip a hole in the roof I could split the beam into sections and bolt together in the roof space, providing it complies with the structural calcs. From that I could bolt a piece of wood to the inside web of the beam and use joist hangers to keep the floor as low as possible.

Any one have any experience of this sort of design?

Hi

That bottom purlin is infact a binder which holds the joists together, it is not there to take any weight off the roof. You can cut sections of this out alongside the existing joists and slot in the larger joists, i would go for 8/3 or 9/2 depending on height restrictions. Also yo need to pack the joists up off the wall plates, i usually use roofing batterns for this, this is to prevent the weight of the new joists/flooring/furniture etc transfering onto the downstairs ceiling boards and also makes it easy to run cables under. If you dont pack the wall plates the 1st floor ceilings will crack in time. Also you must not nail/bolt/screw the new joists to the old, again to prevent weight transfer. Depending on the load bearing walls bellow you may be able to use shorter span joists if this is the case you will get away with 7/2. Once the new joists are in you can then fit a new binder behind the original one to keep the joist stable before laying your floor boards. Remember to space your new joists at 400 mm centers to minimise floor board waste.

Hope this helps

[blasted]

Thanks chaps for the advice. Its looking likely that i will go the full hog and do a complete loft conversion. After trudging through many of the potential issues, there isnt that much to really put a stop to it.

The major aspect will be the floor. Thankfully i have enough headroom to insert a posi-joist floor into the roof space with minimal disruption to the roof, in fact the only disruption is a small section of binder where the stair well is.

if i can get a few quid together im gonna have a bash, plus i found out a structural engineer and architect work in the office below me. cough*cash*cough