Poorly insulated loft that has been boarded over

[adamb4321]

Hi,
I have a house bulit Circa 1999/2000 that has had pretty much all of the loft space boarded over, as 8'x4' boards have been used it must have been done by the builder. I thought this was great till I happened to notice that there is maybe only 50mm fibre glass underneath that doesn't cover the ceiling below properly. The area not boarded has around 250mm
1)Can any one tell me what the minimum depth should have been in the building regs back in 1999.
2) I'm thinking of pulling up the boards to re-insulate, if I counter batten with 3"x2" to increase height for insulation whats the best way to fix the battens to the existing floor joists? (i'm assuming that the battens are positioned with the 3" side verticle?)
3) Would I be able to claim against the NHBC warranty for this?

adam

 

[freddiemercurystwin]

1) Probably about 150mm
2) Screws I would think would be the cheapest, banging in nails will have your ceiling cracking
3) I'd be amazed, NHBC is more for major defects like subsidence etc

 

[adamb4321]

hi freddy,

so just screw through the 3x2" into the joist?

 

[freddiemercurystwin]

Or screw it through the side at angle to save having to drill through the full 3" depth of your battens if you see what I mean. Presumably there'll be a few fixings to hold the boards in place too so you only need to stop the battens/boards moving about, not create a big beefy structural frame.

 

[Deluks]

I think generally speaking the 3x2 is meant to be wide side up, with this in mind you'll probably be fine with 3" screws, like Freddy says the screws will only be preventing lateral movement, gravity will be doing most of the work.

 

[adamb4321]

Is there another insulation product that will offer as good a thermal value as 270mm of fibreglass but with less thickness? I only ask because I'd like the benifits of the better insulation but can't really raise the loft boarding by the 8" required as I assume that all that extra timber used would put too much load on the roof timbers (which after measuring last night are only a shade over 3")

 

[Deluks]

Well removing some of your insulation is a side effect of boarding the loft anyway. But your 50mm is a bit thin. You can get tri-iso type stuff which is claimed to be very efficient and is only an inch thick. Pricey though. As your existing floor is only 3" I'd be very wary of putting anything much more than christmas decs up there. Although we store our garden furniture cushions up there too so you've still got useful storage space for any large, bulky but not too heavy items.

It's possible that the existing floor is structural, providing a diaphram which keeps all the trusses in place. As this could be the case I'd be careful to remove and replace as you go along, don't remove them all at once.

You could for example put down some kingspan/celotex type sheets on top of the existing floor, then overboard these with 12mm chip or 9mm plywood, for storage and access.

 

[adamb4321]

Thanks Deluks,

I'm starting to wish I never looked in the loft at all lol.
I only have a collection of cardbord boxes in the loft at the moment, so weight isn't really a problem.
Can I put insulation over the boards without taking them up, as I only need access to half the loft anyway or will this cause other problems (condensation etc)?
Otherwise this is going to be a big job

 

[Deluks]

Thanks Deluks,

I'm starting to wish I never looked in the loft at all lol.
I only have a collection of cardbord boxes in the loft at the moment, so weight isn't really a problem.
Can I put insulation over the boards without taking them up, as I only need access to half the loft anyway or will this cause other problems (condensation etc)?
Otherwise this is going to be a big job

Yes you can put insulation over these boards, If you read my last paragraph in my previous post then this won't be a very big job at all.

 

[adamb4321]

Thanks again Deluks,
Think I'll put down fibreglass over the half that I don't use as it's the least expensive and celotex and more boards on the half I do use.
Do i just lay the chipboard over the celotex with no fixings?

Adam

 

[Deluks]

Do i just lay the chipboard over the celotex with no fixings?

Adam

I would make a frame of 2x2 marking out the area you want to board over, screw these into the existing floor with 3" screws. Then fix more 2x2 inside this frame in one direction only, spaced 600 apart, screw these down. The celotex comes in 1200 widths, cut this down lengthways. You will then have 600mm wide lengths of insulation, perfect for getting through the loft hatch, and will fit inside your framework. The new chipboard can go on top of all this screwed into the 2x2 frame. The screws are just to stop it all from sliding about, the celotex will take the weight of everything.

 

[adamb4321]

Hi Deluks,

Thanks for all the help/advice,


Adam