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Joists a bit far apart ....


Araucaria
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I want to replace a ceiling/floor in our hangar. It was over the top of a row of stables, and presumably only had fairly light stuff like straw bales on top. The boards that form the current floor are very wood-wormy. Quite a lot of them are missing entirely (the effect of keeping chickens up there I think).

The joists to support the floor are pretty solid oak, and range in size from a width/thickness of 100mm to 150mm: their height/depth is fairly even at about 150mm (think 4x6 to 6x6 in old money). Trouble is, they are at 1 meter centres. The spans are about 2.5 meters, or a bit less.

I'd welcome suggestions for what to use as the new floor/ceiling. Chipboard would be cheap, but would even 22mm panels start to sag eventually across this kind of gap? Has anyone experience with OSB? Or will it have to be plywood if I can't afford real planking (and I don't think I can)?

I appreciate that at present I am telling myself that I don't need to put anything heavy up there, but I know that over the years the clutter just starts to accumulate until an elephant wouldn't be out of place.

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[quote user="f1steveuk"]I'd be inclined to put some "noggins" in running the other way, but I always tend to over-engineer everything I do!!
[/quote]

I would be inclined to add some more joists, I too tend to over engineer everything I do.

Stirling board sags too as would most sheet material over that span.

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Thanks for the suggestions, but .....

Noggins would be possible, but I'd need to use metal joist-hangers to hold them - at extra expense. The oak joists are very hard indeed and drilling right through them would be tough work.

While the idea of extra joists is sensible, the existing joists are built into a schist wall at either end. In fact, it looks very much as if the builders got up to that level, put the joists in place, and then built up around them. Schist is difficult stuff to cut sockets into.

Maybe it will have to be planks after all - the current wormy ones must be a good 60 years old, and I'd be happy if what I put up lasts half that long.

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I have just replaced all the joists in our lounge and am about to do the dining room ones, my centers are 16-17" so yours are a bit bigger.  I wouldn't use OSB and 22mm ply is about €90-00 a sheet so planks would be cheaper, I have been told boards can be had for €20/m2 if you shop around and are not too fussy about finish.

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Noggins? There is no way I could drive a nail through six inches of 100 year old oak (possibly older). I can't get a nail in more than (about) an inch and a half.

I think it will be planks after all, despite the cost - and that's what it was before.

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If you can afford to lose a wee bit of height, why not run  63 x 75mm chevrons across the existing joists, then lay 18mm OSB or chipboard over them.

If width is 2.5 metres you'll need 5 chevrons on 60cm centres. Brico Depot lists 63 x 75 chevrons of 5 metres at 8€10, so cost is 40€10 for each 5 metres of length of the building, which, with the OSB is probably cheaper (and quicker) than planks.

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[quote user="Araucaria"]IIt was over the top of a row of stables, and presumably only had fairly light stuff like straw bales on top.[/quote]I can't help you with the expert stuff but I can tell you that hay bales are extremely dense and heavy (unlike their straw counterparts) so most hay lofts were pretty sturdy.  The groom would walk along in front of the stack and fork the hay into the mangers below so they had to be able to take humans walking about also.
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[quote user="Araucaria"]Noggins? There is no way I could drive a nail through six inches of 100 year old oak (possibly older). I can't get a nail in more than (about) an inch and a half.

I think it will be planks after all, despite the cost - and that's what it was before.

[/quote]

Not right through the joists "toe nailed" from the joist side?

Of course if you buying enough wood to noggin it all, you could just cross lay the same timber, joist width apart, on top of the old oak joists. Higher floor, but everything has a price.

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[quote user="nomoss"]

If you can afford to lose a wee bit of height, why not run  63 x 75mm chevrons across the existing joists, then lay 18mm OSB or chipboard over them.

If width is 2.5 metres you'll need 5 chevrons on 60cm centres. Brico Depot lists 63 x 75 chevrons of 5 metres at 8€10, so cost is 40€10 for each 5 metres of length of the building, which, with the OSB is probably cheaper (and quicker) than planks.

[/quote]

Thanks Nomoss - I think that is a very good idea. I can afford to lose some height above the floor, as there's plenty of extra space up there, and getting a little extra height below it (between the joists) will be a bonus: the ceiling is fairly low. Presumably the horses didn't mind. And the way you suggest will let me level the floor a bit better too.

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We had Oak beams 1 metre apart and used the chevron idea but at 40cm centres. Over engineered ? don't know, but that was what I read at the time.

The chevrons gave us something to attach plasterboard to whilst still showing off the old oak beams downstairs, and as you say gives the opportunity to do a bit of levelling for upstairs.
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