Loft boarding weight concerns

[simchan101]

Hi

I'm planning to board an area of loft space (about 3m x 3m) in my Victorian house for light storage - suitcases, boxes, etc.

I've read some articles advising battening at right angles to the exisiting joists but I'm concerned that the combined weight of the battens, the boards, and then the stuff I want to store is going to place a lot of load on joists originally designed to support the weight of the ceiling below.

The battens are meant to spread the load but won't the interlocking loft boards themselves spread the load?

In terms of battens, what dimensions should they be? I'm reading about people using 2 x7 or 2 x 8 to create clearance for insulation but that sounds like a lot of extra weight. Could I get away with 2x2 timbers, or are they not required at all?

Any guidance would be greatly appreciated as I have nightmare visions of the whole lot coming down on our heads if I don't do this right.

Thanks,
Sim

 

[tony1851]

If you're not concerned about compressing any insulation, just put the boards on top of the existing ceiling joists. Additional battens do not really do much to spread the load across the joists. Just be sensible in where you put the boarding (try to keep it centred above any load-bearing wall below) and what you put up there - only light, bulky items - suitcases, decs., kids plastic toys etc.

 

[simchan101]

Thanks, Tony.

And if I do decide to add to the insulation, I should use the method you described of additional 4x2s fixed atop and in-line with the existing joists, not at right angles? And this will increase strength and rigidity of the span?

I'm a little concerned as the boards will be centred over the middle of my bedroom ceiling, with the external walls as the only support.

 

[freddiemercurystwin]

tony, what about a very large bulky suitcase full to the brim with plastic toys?

 

[tony1851]

And if I do decide to add to the insulation, I should use the method you described of additional 4x2s fixed atop and in-line with the existing joists, not at right angles? And this will increase strength and rigidity of the span?

Yes; if you can screw 4x2s along the tops of the existing joists (say at 12" c/s) this will increase the strength considerably. You wouldn't need to go end-to-end with the additional timber either.

And yes, with that arangement, FMT, he would be able to cram as much stuff as possible in suitcases - maybe even store an anvil or two up there as well.

 

[simchan101]

Thanks again.

Although I noticed on another thread that FMT disagrees saying there would be no strength gain unless the new timber is perfectly mated with the old joist so it acts as one unit, and that it should be cross-battened instead!

As always, conflicting advice and confusion abounds but what you are saying makes sense to me, so thanks for taking the time to respond.

 

[tony1851]

Thanks again.

Although I noticed on another thread that FMT disagrees saying there would be no strength gain unless the new timber is perfectly mated with the old joist so it acts as one unit, and that it should be cross-battened instead!

As always, conflicting advice and confusion abounds but what you are saying makes sense to me, so thanks for taking the time to respond.

I don't know what your existing ceiling joists are, but let's say 3x2. If you simply laid a second 3x2 along the top, then height-wise the combined joist would be 6" deep. However, it would not act as a solid 6x2. The 2 pieces would both bend equally, and the lower surface of the upper 3x2 would slide over the upper surface of the lower 3x2.

What would happen if we could clamp the two timbers together so tightly that friction between the two surfaces did not allow them to move relative to each other? We would have effectively turned the beam into a much stronger 6x2.

In screwing the two pieces together (say, using 4" screws in counter-bored holes), the screws provide the clamping force to hold the pieces together. The screws can easily accomodate the horizontal shear force at the interface between the pieces, so you have effectively created a much stronger beam. It won't be excactly equivalent to a 6" deep beam because of the holes you would need to drill, but it would be as near as dammit.

(Phew! I feel exhausted now!).

 

[simchan101]

Haha, yes, that was a full explanation!

I understand exactly what you're saying and it makes more sense to me than the cross-batten approach.

How deep should the counter-bores be? I can't seem to find the thread with your picture now!

 

[tony1851]

Untitled

• tony1851
• 23 Apr 2013
• 1