Can I lay loft insulation over loft boards

badatDIY

I've been given some spare 200mm loft insulation by someone who bought too much for their own loft. My loft is currently insulated to max 150mm with boards on top of that. I could theoretically take the boards up, but before doing all that faff would the insulation still work okay if I just laid it over the boards? Appreciate that "doing it properly" is almost always advised but I'm much more likely to do this bodge in the short term and fix it properly in the long term, but will the bodge be pointless?

grumbler

badatDIY said:

Appreciate that "doing it properly" is almost always advised but I'm much more likely to do this bodge in the short term and fix it properly in the long term, but will the bodge be pointless?

I'm a perfectionist, but I don't see any problems with adding insulation over the boards and this surely isn't pointless. The only problem is that you lose storage space.

To do this 'properly' you need loft legs to rise the boards level, that is a much bigger job.

badatDIY

grumbler said:

badatDIY said:

Appreciate that "doing it properly" is almost always advised but I'm much more likely to do this bodge in the short term and fix it properly in the long term, but will the bodge be pointless?

I'm a perfectionist, but I don't see any problems with adding insulation over the boards and this surely isn't pointless. The only problem is that you lose storage space.

To do this 'properly' you need loft legs to rise the boards level, that is a much bigger job.

Thanks!

Not bothered about losing storage space, we only keep a few small boxes up there anyway.

My only concern is would it affect ventilation? Eaves are clear, but presumably raising the level of the "floor" could stop air circulation?

MikeJXE

Yes you can, do the boards squash the insulation under them, ? If so it's not working how it should 

badatDIY

MikeJXE said:

Yes you can, do the boards squash the insulation under them, ? If so it's not working how it should 

I've not looked that closely but I suspect it does yes

MikeJXE

badatDIY said:

MikeJXE said:

Yes you can, do the boards squash the insulation under them, ? If so it's not working how it should 

I've not looked that closely but I suspect it does yes

The insulation over the boards will work as it's meant to, the insulation under the boards won't work as 150mm is meant to,

if it was me I would take the boards up, remove the insulation, replace the boards then put the insulation on top. Failing that you need to ensure any boarding is higher than the insulation they cover 

FreeBear

Loft legs are often one of two sizes - Either 175mm or 300mm. Assuming you have 175mm legs with 100mm deep joists, I would expect there to be a gap between the top of the insulation and the loft boards of 100-125mm. There is likely to be quite a bit of breeze blowing around in that space which needs to be filled otherwise you'd be wasting your time putting insulation down on top of the loft boards.

BUFF

You can also get a similar product, loft stilts, which are 270mm.
You do want some space for air movement between the insulation & the undersides of the boards.
Imo if you are going to go to the work of fitting loft legs/stilts & boards do the job right even if that means removing/redoing existing.

badatDIY

There's no way I'm gonna do loft legs right now. Maybe in the future, much more likely hiring someone else to do it in the future.

So for now it seems to be the case that it'll probably make some difference to put the insulation on the boards and that'll have to be good enough. Thanks all