Which screws to use for loft boarding?

[perlmonkey]

Hi all,

I'm new here and also new to DIY.. I'm just about to get started on boarding out my loft but I'm not sure what size and type of screws would be best.. the boarding is purely for light storage space.

My joists are 1.5" x 4.5" and I'm laying 34mm x 34mm battens across the top. The boarding is standard 18mm chip board.

I assume standard wood screws will suffice but what length and type should I be using?

I thought perhaps the best way would be to first screw down the battens into the joists, and then screw the boarding into the battens, that way I can avoid using massively long screws, and it will be easier to avoid screwing into cables or pipes. Does that sound right?

(Additional Note: I should also perhaps be careful about using too many screws and/or going too deep into the joists, to avoid weakening them, as I have no additional support on the joists. A structural engineer has assured me it will be fine without, since my storage weight is fairly low..and he's given me a 20kg per m2 limit.)

 

[big-all]

113+34=147mm or 5 3/4"

screwing 34 would use 70mm4.5mm or 3" 8s
for 20mm board 50-60mm 4.5mm or 2 1/4" no 8s
see youve edited your post since earlier lol[20x44]

 

[perlmonkey]

113+34=147mm or 5 3/4"

screwing 34 would use 70mm4.5mm or 3" 8s
for 20mm board 50-60mm 4.5mm or 2 1/4" no 8s
see youve edited your post since earlier lol[20x44]

Thanks I can place my order for screws and an impact driver now from screwfix, maybe get started this week.

I asked the timber yard to give me 47mm x 22mm but they actually sent me 34mm x 34mm and it says on the invoice 38mm x 38mm but I guess there's always a bit of variation wood is not precise is it, shrinkage etc.

Anyway.. this now raises another question about whether 34mm will provide sufficient clearance for my piping in the loft.. I'm going to have to post a picture and take some measurements... perhaps then your good self or someone else can advise me whether I should be yelling at the timber merchant

 

[big-all]

if its planed timber then thats the stock size [3-6mm smaller] thats why 2x1" planed is 21x44mm

1 1/2" waste pipe is 40mm
you cannot risk notching your timbers

but would be happier with a 7mm slot under the flooring as its only storage and iff any cracks appear cover with 12mm ply between joists on top off the flooring

 

[JohnD]

maybe it is overflow pipes from the tank? 18mm or so? if you notch or drill your counterbattens it will not be so bad as you are not weakening the roof structure.

Modern trussed roofs are designed and manufactured to use the minimum possible cost, material and strength that is just enough.

btw the 45mm is deeper, stronger and more rigid than the 34mm stuff they sent you. It's wrong. Send it back.

 

[perlmonkey]

Thanks for the replies and help guys, I appreciate it.

Well it seems I sort of made a slip up when I placed my order for the timber I said if you have 38x38mm send that, if not, send 47x22mm.. I knew looking at these dimensions they would provide sufficient height and be strong battens, but without adding too much weight..

So it seems the timber yard supplied what they thought was closer to 38x38 but as you say, it's been planed so it's now 34x34.

Anyway, I've just been in the loft with my ruler and camera to see how much clearance these battens provide over the pipes.. (not sure if the pipes are gas or water, perhaps someone can tell).. the clearance is pretty close (see below) but since these pipes are only in a small area of the loft I guess I could mark them off and avoid storing anything or sitting on them.

As for the batten timber itself, as John said earlier they are not that strong compared to 47mm..but light storage and someone light (9.5st) walking on them such as myself shouldn't be a problem? I will be putting the battens a foot apart under the sheet and the joists themselves are 22 inches apart.

Here you can see a junction thing on the pipes which stands a bit higher than the pipes themselves.. resting a credit card on it I measured to the top of my batten which is flush on the joist...the batten gives just 5mm clearance from this junction thing. You can't see the actual clearance height too well on this photo from this angle but at least it makes it easier to see what I'm on about..


Measuring the same way from the top of the pipe using a credit card, the battens provide 1cm of clearance.

So what do you guys reckon? Do you think it would be ok just to go ahead and use them, or should I definitely get more clearance and get some 47mm battens?

 

[Monkeh]

Are those cables black, or is it just the light?

 

[perlmonkey]

Are those cables black, or is it just the light?

Yes those big black cables are heavy duty power cables.. there's quite a few of them over the joists in various places but the battens provide loads of clearance over those..

 

[Monkeh]

Are those cables black, or is it just the light?

Yes those big black cables are heavy duty power cables.. there's quite a few of them over the joists in various places but the battens provide loads of clearance over those..

Flat and black suggests VIR. Also, you shouldn't be hiding inspection joints and junction boxes.

 

[big-all]

metalic pipes are electrical conduit [trunking]
you should mark everywhere theres an access plate on the pipes thats assuming the conduit is still in use

 

[Monkeh]

black pipes are electrical conduit [trunking]

Definitely not trunking.. And I see galv, not black enamel.

 

[perlmonkey]

black pipes are electrical conduit [trunking]
you should mark everywhere theres an access plate on the pipes thats assuming the conduit is still in use

I will do as you suggest and mark it all out clearly on the sheet and not store anything there as could be services access needed in future for other flats maybe..

 

[big-all]

black pipes are electrical conduit [trunking]

Definitely not trunking.. And I see galv, not black enamel.

sorry meant the metallic

all joins must remain accessible in case off problems

 

[perlmonkey]

black pipes are electrical conduit [trunking]

Definitely not trunking.. And I see galv, not black enamel.

sorry meant the metallic

all joins must remain accessible in case off problems

Would you avoid screwing boards down over them then? Perhaps I should I just rest boards over those for quick access?

 

[big-all]

the chances are you wont need access but it will save you a fortune when an electrician is fault finding and needs to know where to look lol