Polystyrene sheets in loft

[greggx101]

Wondered if anyone could kindly help...

I have bought an old house (1960) and the loft has lots of large polystyrene sheets covering the pitched cieling of the loft if you know what i mean ( the rafters ? )

The floor of the loft is insulated normally and boarded out.

Some of these polystyrene sheets on the rafters on the roof has fell off and some missing, exposing worn felt then in some places the roof tiles.

I wondered.....

1. What is this stuff ?
2. Is it legal now ? Is it a firehazard ? If so...
3. Should i try and source replacement sheets for the missing ones - if so where ?
4. Should i just rip it all down and maybe ply the whole area ?


Thanks Alot

GX
4.

 

[MickBee]

Factors to consider include insulation, moisture and ventilation and roof loadings.

You should either have a “cold loft space” with insulation on the floor (common for a storage loft), or a “warm roof space” with insulation on the walls/roof (for a habitable room); the belt-and-braces approach of insulating both floor and walls is NOT advisable because there is a risk of condensation leading to rot damage. This link http://www.roofingmag.com/news/newsview.asp?id=106 has more info.

I assume that your loft is only to be used for a little light storage (i.e. not as a habitable space, in which case loft conversion rules would apply.) As you say that the floor of the loft is insulated normally and boarded out, it would seem that your best approach is to have a “cold loft space” (above the insulation/flooring) and this space needs to be ventilated to prevent condensation causing mould & rot damage.

The polystyrene sheeting is probably (a) hindering ventilation, and (b) doing little to help insulation, if there is a decent depth (10"/250 mm) of fibreglass on the loft floor.

To answer your questions directly:

1. What is this stuff ? [Can’t tell without a photo (maybe not even then)]
2. Is it legal now ? Is it a fire hazard ? If so... [I don’t know]
3. Should I try and source replacement sheets for the missing ones - if so where ? [NO - for reasons above]
4. Should I just rip it all down and maybe ply the whole area ? [YES to ripping it down and definitely NO to replacing it with ply. The ply would be worse because it would add a significant load to the rafters and would cut down on ventilation, while being expensive and having no particular benefit.]

If you are concerned that removing all the polystyrene sheeting will make the loft space too well ventilated (where the roofing felt has gone) and that there will be too much dust blowing around, you might want to consider tacking up something like gardening fleece or fine mesh netting, which will be light and will still allow some ventilation. [Also, if there is only 2”/50 mm of fibreglass on the loft floor, it would be a good idea to top it up.]