so where do you get the 3.5m maximum span?

half of 8.2 is 4.1, am I being dense?

Does this help.

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The big thick line is the main bean, and the little lines are walls below.

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ahhhhh, thanks.

well 2x4 will probably be ok, but it you are going to all that effort, why not go 5X2 so you have that much more strength there.

fitting them with joist hangers is exactly the same ammount of work, and the cost in materials is a negligable difference.

Where abouts are you, I have 3 full boxes of joist hangers just sitting around that would do this, (were going in a skip on a job I was on over a year ago), you could grab what you needed for a drink.

oh, ok I just saw your location, probably too far :)

Assuming that the walls below would take the load, for a proper domestic floor load (of 150kg per m2) you would need 6x2 joists @ 400centres to span 3.5m.

Scaling this down, (load capacity is approx proportional to depth squared):

a 5x2 would give you 25/36 of 150kg = 104kg per m2
a 4x2 would give you 16/36 of 150kg = 66kg per m2

This sounds a lot, but for perspective 66kg per m2 is equivalent to 36mm of dry sand! It depends on what you plan to store. Don't get too carried away since the load will be carried by your stud walls and ultimately by the 1st floor joists.

I would suggest putting the new joists at the side of the existing, ensuring a full 100mm bearing on the wallplate. If you need to remove any ceiling binders (timbers that span the opposite direction on top of the ceiling joists) or hangers, you must fix the new joists to the old to stop your ceiling sagging.

If you have no vapour barrier below the ceiling insulation, ensure you leave a ventilated gap between the top of the insulation and the underside of the boarding otherwise you will get mold on the underside of the boards.

Hope it helps,

Steve

Cheers for the help lads it's much appreciated. It's been a bit of a funny one because of the original setup.

I would have suspended the whole thing from the neigbouring walls with 5x2 / 6x2 but I can only really get a length of 4.2 into the loft without going through the roof which seems like a hasle for whats it's going to be used for.

Steve it's only going to be for storage. I did think about doing the whole conversion a couple of years ago when renovating but it will probably need rsjs and and a full over haul to be honest.

The storage is only going to be used for things such as christmas decor, camping stuff, golf clubs etc y know the usual stuff.

I can walk around it it at the moment ok (and that's 3x1) but it's not boarded and I think the extra weight may be a little too much. plus the insulation we've just had put down is 10 inches thick.

I don't particularly want to go to 5x2 mainly because the floor to floor height will increase to over 10ft (5x2 would probably have to rest on top of the beam) which is too much for standard loft ladders. (does anyone know where I could get longer ones without spending an arm and a leg).

The other thought that I had was to hang a 3x2 joist directly above the existing ones with a hanger and put a wedge in every 4 ft if that makes any sense (every 4ft would be supported be exisitng joists). Would that be suitable??

Finally would everyone use the chip board or OSB/sterling board? for the flooring. I was thinking OSB cos it's lighter.

Cheers again for all of the help.

BTW Cheers for the offer of the hangers python but it would be cheaper me just buying them up here.

Why, you can but joist hangers for any size timber.

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I didn't want it to go over the height of the central beam

Having slept on it think I'll definitely have to use the 4x2 and sit them on top of the central beam. Does anyone know where I can buy loft ladders which will do a floor to floor of between 320cm - 350cm?

Most are limited to 300

I would think the governing factor would be the outside wall height and the level to the center beam.

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I'm going to have to have a look into that. I may not be able to rest a beam actually on the wall.

The whole thing is a bit of a nightmare which ever way I look at it.

Anyone got any ideas if I can't do that?