Roof/Ceiling Joists

[sam8364]

Hi,

My in-laws have just moved into a 1980/90s build modern house having (like me) always lived in victorian properties.

I nipped up into the loft for them yesterday to see if had been previous boarded (which it hadn't) and was horrified to see that the joists (the ones to which the first floor ceiling is attached) are only about 2-3 inches deep. I guess that this the modern building method but I concerned about how much weight can be put in the loft.

They intend to board it out and use it for general storage - but where we are used to chucking any old thing of any weight, anywhere in the loft , do we need to be more careful on what it up there and how it is distributed?

Any advice greatly received.

 

[masona]

I nipped up into the loft for them yesterday to see if had been previous boarded (which it hadn't) and was horrified to see that the joists (the ones to which the first floor ceiling is attached) are only about 2-3 inches deep.

Sounds like thjey are roof trusses gang nail plate, can you see the plates?

I guess that this the modern building method but I concerned about how much weight can be put in the loft.

The idea of the cleverly design of the gang nail roof trusses is to save timber wastages plus labour saving.

Let us know what type of roof you have then we can help you.

 

[sam8364]

Yep, looks like that sort of roof - certainl very busy with diagonal bits of timber unlike the relatively clear victorian roofs.

We are not wanting to use the loft for anything other than general attic type storage but was just a bit concerned about how much weight these joists will take. This horizontal timbers that support the ceiling can only be 1.5" x 3"

 

[JohnD]

Those engineered roofs have been carefully calculated to use the minimum timber at minimum cost, and to be (just) strong enough to hold the weight of the tiles and the ceiling and withstand reasonable winds. When a fat builder clambers about on them they bend.

You will probably find that if there is a water tank up there it has extra trusses or spreaders to take the weight.

You can counterbatten (lay new timbers at right angles to the trusses) before boarding, this will help spread the weight of spot loads (and also give you more depth for insulation) but it will not be strong enough for a habitable room or anything heavy.

Look for where the intermediate walls are, and try to centre any weight over them, not in the middle of an unsupported length.

It will be OK for storing your Xmas decs though

 

[sam8364]

Cheers chaps, we were not intending to use it as a habitable room. If boarded without counter battening will it be strong enough to hold my 14 stone when clambering about in the loft storing things?

When you say will not take anything heavy? Is that with or without the counter battening - and how do you define heavy?

How should you attached counter battening? With what size timber and at what space intervals?

 

[JohnD]

The counterbattening will not make it stronger as a whole, but it will spread the load, so if you stand on it, your weight will be on three timbers instead of one.

You can counterbatten with pretty well anything handy. My local merchant had a lot of 35mm x 70mm construction timber going cheap, so I used that. Other people use 100mm x 25mm or 50mm x 50mm. The deeper it is, the more room you have for insulation between the ceiling and the loft floor. You have to fix with screws (drill pilot holes first) as hammering nails in will probably crack the ceiling plaster. If you use second hand timber I would treat it, and the loft, against woodworm. The more firmly it is all screwed together the more rigid it will be and the better it will spread weight. But remember that the flloring itself increases the load up there.

My preferred spacing is so that you have a batten half under the edge of each board, and one in the middle. So if your loft boards were 900mm wide, you'd put the outer ones at 900mm centres. and one (about) the middle. The spacing of the middle one does not have to be precise.

Packs of T&G chipboard slabs for loft floors are sold at timber merchasnts and DIY sheds. If you can carry an 8'x2' piece of flooring chipboard into the loft (they are quite awkward) it will be cheaper, and, having fewer joints, perhaps a bit stronger too. Chipboard does not stand up to damp but a newish house is likely to be felted.,