Boarding out a loft

[OldKettle]

Hi,
I am planning to board out the loft of a house (please see pictures below), so that I can store household goods up there.

Do I simply need to buy some boards and screw them to the joists, or is there more to it? (I will be checking and possibly replacing the insulation, if it is not thick enough)

How would I select the correct boards for the job?

The loft is about 50m2. How much do you reckon the materials should cost?

Any thoughts would be much appreciated.

 

[Doggit]

You want a bit more insulation up there first. Add some 4x2 on top of the joists, put in 170mm of rockwool, and squash it down, and then board the loft out. Someone's already got a board up there, so you can get long boards in easily, but make sure they end on a joist so that you don't put your foot on an unsupported end, and go through the ceiling.

 

[Diver Fred]

As you are talking about using the loft for storage you also need to decide do you want a cold or warm loft storage.
If cold then do as Doggit suggests in #2.
If warm is your preference then you ought to use cellotex or similar on the underside of the rafters, I see that there is some peices of what looks like mineral firestopping sheets affixed to the rafters. Check that there is ventilation from the edges of the roof before you do that though.

Once that is complete then you can either use your choice of loft flooring panels, T&G flooring or 19/22/25 thick timber planks. Fix with 1&3/4inch No8 screws. don't trap electrical cables.

 

[OldKettle]

As you are talking about using the loft for storage you also need to decide do you want a cold or warm loft storage.

Thanks. After Doggit's post last night I had a look online regarding insulation and came across the cold/warm loft issue. I think that I will go for a warm loft.

In that case, am I correct in thinking that I need to remove the insulation that is between the joists before laying the flooring?

Check that there is ventilation from the edges of the roof before you do that though

Thanks, I hadn't realised that I needed to check for this. What is the best way to check?

Once that is complete then you can either use your choice of loft flooring panels, T&G flooring or 19/22/25 thick timber planks. Fix with 1&3/4inch No8 screws. don't trap electrical cables.

I want to make sure that the flooring is decent, but don't want to over-engineer it or spend more than I need to.

Would something like this be OK (for about £8 per sqm)? http://www.wickes.co.uk/Wickes-Chipboard-Loft-Panels-320-x-1-22m-Pack-of-3/p/116420

Or are there any better/cheaper options?

 

[Doggit]

Woah, slow down OldKettle. With the cost of Cellotex nowadays, this job could become an arm and a leg. You don't normally bother creating a warm room, unless you want to occupy it, and if you're just after storage, then leave it at a cold roof. Creating a warm roof just for storage is way over the top, and completely unnecessary.

It looks as though you have felt under the tiles, so you'd need to start battening out the rafters sufficiently to allow a 2" air gap under the felt to give a good airflow up and over the Cellotex, and with the ridge board stopping that flow at the top, you've then got to create a mini roof to get past that. You don't have a lot of height in the roof, and battening the rafters would lower it even more, plus you've raised the joists. The caveat here being that you wouldn't need to go for 135mm or cellotex, and could get away with maybe 60mm (and wouldn't need to batten), but you'd still need to up the insulation between the joists, or you're heating the loft space for no beneficial reason.

So take a step back, sit down, and take careful stock before you go any further.

As to the loft panels; they're easy to use, but will they sit on the joists properly. I did a small loft last year, and glued all the short edges because the loft was so small, that no one would ever stand upright in there, but I don't think that would be appropriate for you. Go for 18mm T&G chipboard, and just trim one end every now and then, or put a couple of noggins under the ends to support them, and keep the T&G going.

 

[OldKettle]

Thanks Doggit. I appreciate the recommendation for the flooring. Looks good.

As for the warm/cold loft issue, I always have an eye to future proofing. For now, I am probably just going to store standard household items, but I may also store electronics up there and it would be good to future proof it if I decide to make other use of the space.

However, if I understand correctly, then for warm storage I would need to insulate between the joists too, but not if I wanted to use it as a room.

For now, I might just keep the existing insulation and partially board out (just enough for my current storage needs), and then decide longer term on whether to make it warm storage/room.

If I did that, do I need to batten down the existing insulation to leave an air gap under the new boards?

 

[JP_]

That's a nice space!
Do you have room for stairs ....

 

[Doggit]

I don't know what the exact regs are, but I believe you still need insulation in the flooring, even if you're creating a warm room. If you're not going to increase the height of the joists, then maybe just add what you can to the exiting stuff, and see how much you can squash in, but you don't need to leave an air gap afterwards. Basically, you need to insulate whether it's a warm or cold room, it become a case of, just how much. Treat the area as a cold storage for now, and then you'll be fine for the next stage, but remember, unless you install proper joists, then it'll never be a habitable room, but gluing and screwing 3x2 or 4x2s to the existing joists, will be a good interim stage, ass you never know how much the next person is going to put up there.

 

[Diver Fred]

OK.
The quick way to check for ventilation into the loft edges is from outside look up to the 'Sofits' (the flat sheets that go between wall and the facias }facias are the stuff the guttering is fixed to{) and see if they are vented. If they are then all wel and good.

The reason I suggested considering a 'warm' roof is from experience, If you are using the loft space for storage then the cold loft will affect the stored items quicker than in a 'warm' loft.
I used celotex in our loft to make it a 'warm' loft as the wife stores 'seasonal' clothing in the loft.

If you do the same then I'd not recommend increasing the thickness of 'on ceiling' insulation. Do reinforce joists if you are going to store heavy items - as others have indicated uping the depth of joists to 6 or 8 inches. Screw the reinforcing to the existing joists at regular intervals.

 

[JP_]

Yeah, of you plan to store books, paper, clothes etc then you don't want it freezing cold, and need to avoid moisture problems.

 

[Doggit]

Actually, it's amazing what can be stored in a cold loft without moisture issues. As long as rain etc isn't getting in, then it should be cold, but not wet.

But Wgt52 makes reasonable sense.

 

[OldKettle]

Thanks again for all of the advice.

I am hoping to get moving on this at the weekend, and have measure the existing joists which are 2x4 and spaced about 40cm apart.

How important is it, that I increase the depth of the joists, if the loft is just to be used for storage (and obviously supporting people walking around)?

If I do need to increase the depth of the joists, would these be appropriate and what screws do I need to fix them to the existing joists?

http://www.wickes.co.uk/Wickes-Sawn-Kiln-Dried-47-x-100-x-2400mm-Single/p/107187

EDIT: Also, are these OK for fixing the boards to the joists? Do I need to pre-drill holes?

https://www.screwfix.com/p/goldscrew-pz-double-self-countersunk-woodscrews-4-x-45mm-200-pack/17178

I also took some new pictures.

 

[OldKettle]

Hi,
Just wondering is anybody can advise on whether I just need to increase the depth of the joists by screwing something like this existing joists?

http://www.wickes.co.uk/Wickes-Sawn-Kiln-Dried-47-x-100-x-2400mm-Single/p/107187

Do I just screw them on-top of the existing ones, like this? Does the new wood need to be continuous between the walls/supports, or can it have gaps as long as it increases the thickness of the joist?

 

[Doggit]

If you're doing the job even half properly, then you want to up the insulation, but you can't do that to regs, and also up the joists to the necessary height. My suggestion is always to add a 2x4 glued and screwed onto the existing joists, and then add another 100mm of cellotex, and then add the boards, or put in 170mm, and sqaush slightly before fitting the boards. It's as much the airgap that traps air to keep you warm, as the amount of insulation, so sqaushing it in theory may not reallly improve on just another 100mm

 

[OldKettle]

Thanks Doggit. Does the new 2x4 need to be continuous between the original joist's supports, or does it still add the same support if there are breaks in the additional 2x4. I mean breaks rather than actual gaps. The span between the supports is just shy of 3 metres, so I'm wondering if I need to add a 2x4 that is at least 3 metres of whether I can use shorter lengths.