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Boarding out a garage for storage - any structural engineers here?

Community Veteran
Posts: 6,822
Registered: 27-10-2012

Boarding out a garage for storage - any structural engineers here?

I have a technical question regarding loaded weights.
We have a fink truss roof and want to put some chipboard over the middle part of the garage for light-medium weight storage. According to our plans, the bottom member of the truss is designed for  a "ceiling and nominal insulation of 0.25 kN/sq.m (5lbs/sq.ft.) and a superimposed load of 0.25 kN/sq.m (5lbs per sq.ft)". I've been told this basically means it's not designed for storage.
So what are my options? Is there any way of strengthening things or putting some kind of independent beams in?
Thanks!
8 REPLIES
WTF
Grafter
Posts: 673
Thanks: 1
Registered: 14-09-2012

Re: Boarding out a garage for storage - any structural engineers here?

Non-techical response: could you double up the layers, with the 'grain' crosswise?
Community Veteran
Posts: 6,822
Registered: 27-10-2012

Re: Boarding out a garage for storage - any structural engineers here?

I don't think that would work unfortunately.
The joists sit level either side of the garage above the brickwork. So I could only bolster them up above, but there are joists tied in with nail plates above so I couldn't span the whole length.
WTF
Grafter
Posts: 673
Thanks: 1
Registered: 14-09-2012

Re: Boarding out a garage for storage - any structural engineers here?

How about bracing between the joist?
Of course, given the amount of wood and work that would require, you might be better off buying heavier gauge chipboard  Undecided
CX
Grafter
Posts: 745
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Registered: 16-09-2010

Re: Boarding out a garage for storage - any structural engineers here?

Does it currently have a ceiling and insulation?
I'd just use the lightest (thinnest) board you can get away with without it flexing too much, and don't put too much up there.
(although the other argument is that thicker and hence heavier boards properly fixed down, as opposed to a lighter board just laid over the joists, may not have much detrimental effect as the increase in dead load would suggest)
If it were me, I would board it out in a way that you don't need to physically climb up onto the board, so have a central (or several) openings for lifting up boxes.
I'm not a structural engineer, I just play one at work.
Community Veteran
Posts: 38,239
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Registered: 15-06-2007

Re: Boarding out a garage for storage - any structural engineers here?

what is the distance between the walls
what is the wall construction and is there sufficient headroom to consider an additional beam or beams just under the existing truss which could be supported from the walls
there are several ways of doing that depending on the construction
Community Veteran
Posts: 6,822
Registered: 27-10-2012

Re: Boarding out a garage for storage - any structural engineers here?

@WTF I think the chipboard would act as the brace anyway.
@ CX  No ceiling/insulation at the moment. I would have thought that the 0.25 kN/sq.m would be designed for plasterboarding the ceiling anyway? I think our main loft space is the same and we have boarded that out without any issues. But we do have a fair few internal walls in padstone so I think the weight is better supported.
@ Oldjim It's a big garage - 9.1m x 7.2m. I don't think you normally get structural timber in that length (7.2m) so what they have done is put two lengths of 3.1m (4x2") joined with a nail plate. Walls are breeze blocks at the sides/rear and an RSJ on pillars at the front.
Community Veteran
Posts: 38,239
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Fixes: 54
Registered: 15-06-2007

Re: Boarding out a garage for storage - any structural engineers here?

In which case you would need to consider steel joists and a professional installer as they would be heavy
Community Veteran
Posts: 6,822
Registered: 27-10-2012

Re: Boarding out a garage for storage - any structural engineers here?

I'm not sure if I would be able to put in another steel joist as the front of the garage already has a 6m rsj and and 3m catnic rsj on pillars. I was looking at some kind of engineered joists or glulam joists on here http://www.jji-joists.co.uk/index.php/technical_info/interactive_span_table. But the braces across the bottom chords would be in the way (I think).