Loft Boards and cable above joists

[gidrae]

I bought some loft boards the other day, but am finding cables underneath the mass of insulation that sits above the joists. To stop crushing the cables.

I was thinking of cutting small squares (the width of the joist) that I can screw into the joist, then place the boards on top of the squares and screw into them to raise the boards from joists.

Does this seam a reasonable idea?

 

[Gobo]

If there's lots of insulation and you planning on laying over the top, check your not crushing it too much as it could put a lot of pressure on you ceiling.

Best thing to do is to raise batten it, which by your description your kind off planning to do.

but first, I'd check there going to be adequate space for the insulation under the boards before working out how high to raise them, normally a couple of extra inches would be needed.

Gobs

 

[mointainwalker]

If you have any cables under insulation you are at risk of the cables overheating and causing a fire.

In reality the risk with lighting cables is slight, but if you have major current-carrying cables as for an electric-shower then these should ABSOLUTELY NOT be buried.

 

[stevec59]

I have just moved into a new house and am thinking about putting flooring in the loft, I was thinking of using:-
http://www.wickes.co.uk/invt/164516?WT.ac=SP030005

At 2.4 m long I guess thet will be heavy, so I plan to measure the gap between the joist and cut the boards so that the can be easily be lifted in to the loft and to that the end of the bord is in the center of a joist (might cut the board more than 1 place if its too heavy).

I haven't been in the loft as yet, but I guess I will have cables over the joists as well, one thought that I had was tocut a small groove in the Joist and put the cable in the groove, is this not a good idea? I guess the other option would be to screw battens to the existing joist raising the level so that the cables aren't crushed ( is that what you mean in your post), if so, i guess I would need to put a battern on every joist, will they be 4" x 2", if so I guess I will need 2" x 2" batterns.

Also I wasn't sure what sixe screws to use, as the floor boards are 18mm, I guess 30mm? What about head size? 3mm or bigger?

Thanks

Steve

 

[Gobo]

The reason for cross battening is just to allow for the insulation and wiring as an add on, you can chop grooves into the joists if you feel the insulation isn't going to be heavily compacted, just remember to mark on the boards as you lay them where the wires are to prevent screwing into them.

http://www.screwfix.com/prods/13297...rews/Goldscrew-Countersunk-3-30mm-Pack-of-200

Something like this for the screws, pre-drilling the holes with a 3to4mm bit will make it countersink alot easier and ensure the board is pulled tight to the joist or batten.

If you going to end up chopping those boards up in to pieces you'd be better off using, http://www.wickes.co.uk/Loft-Panels/invt/116420. They only work out about 15p more a square meter. In places where you want to leave access you can just remove the lower part of the tongue so it can be lifted.

Hope this helps,

Gobs

 

[stevec59]

Thanks, I did look at that floor board, but the one I have put a link to is on offer if you buy 10 or more boards and its P5 grade (whatever that means) and water resistant, with the green top, I thought it might be extra water resistant, not that that matters I don't think!?

Also, i was talking to a friend of mine the week end, who said that you aren't supposed to board out lofts, it puts extra stain on the joists and lofts aren't desinged for storage..Any Thoughts?

Thanks again..Steve

 

[Gobo]

If your only using it for storage it should be fine, cross battening it would give it some extra strength where your planning to put the boards down. You just don't want to be jumping up and down up there. How old is the property?

New builds a generally built to be strong enough up there for storage and access, older properties also have the strength for access as most at some point or still do have a heavy expansion/overflow tank up there for the central heating which would need to have safe and adequate access for maintenance etc.

 

[noseall]

if you have major current-carrying cables as for an electric-shower then these should ABSOLUTELY NOT be buried.

I find this difficult to believe.

Surely the cable would need to wound tight, bunched up or clumped together to achieve this?

 

[mointainwalker]

Just ask on the electricians forum noseall, this is a reasonably frequent topic.

Cables give off heat: if they cannot dissipate it, as when under insulation, this degrades their ability to carry current and can lead to overheating if they were initially rated as being in free air.