Internal insulation of an old flat roof

[Nicebutdim]

Been watching hubby struggling to insulate bedroom ceiling and could do with advice to prove what a helpful wife he has! He's using Superquilt, has successfully stapled it over nasty artex ceiling. Then tried screwing 2 inch sheets of Celotex to it but this tears the foiling of the quilt and kinda defeats the object. Plan to plaster board over top of this. Reluctant to use nails as boarded ceiling in last house sagged after about a year. Any suggestions please??

 

[freddiemercurystwin]

You're saying you have an existing flat roof with artex on the plasterboard beneath the joists. To the face of the plasterboard well-meaning hubby has stapled superquilt and now wants to fit a layer of celotex

Firstly superquilt is designed to have an air gap either side of it not get squashed between a ceiling and some celotex so bit pointless using that superquilt tbh. You can just stick some aluminium tape over the screw heads but he really shouldn't be hammering them up tight you just need a few to hold it in place until you get the boards up. The screws holding up the plasterboard that screw into through the celotex into the joists will be doing al the work.

Hope the void between the existing ceiling PB and the underside of the roof deck is gonna be properly ventilated otherwise condensation (and timber decay) will occur.

 

[Nicebutdim]

Thanks for your reply!

"freddymercurystwin" You're saying you have an existing flat roof with artex on the plasterboard beneath the joists. To the face of the plasterboard well-meaning hubby has stapled superquilt and now wants to fit a layer of celotex

Yes, that's correct. As far as we're aware there was no insulation at all above existing plasterboards (could feel wind blowing through hole around light fitting), don't know what ventilation is up there but suspect very little, it was built in the early 80's. The roof was recovered externally 2 years ago which stopped the leaks but the room is still freezing cold.

Just to be sure - are you suggesting using a few nails to secure the Celotex to the joists (with the new quilt and old plasterboards in between them) and then screws to hold the new plasterboard over all of this?

Many thanks!

 

[freddiemercurystwin]

Well I wouldn't use nails to hold the celotex up there, you will just shake the existing ceiling/artex to pieces!

Just a few screws per sheet of celotex enough to hold the celotex in place until you fit the plasterboards. Then your plasterboard screws need to be long enough to go through the plasterboard , celotex and (now squashed) superquilt and get a good fixing into the joists.

 

[samdawson3018]

hi there, just to add up, there are several types of insulations available: standard, which also provides good sound insulation, and new technology, which is quicker and easier to install.
How it works

Standard – insulated plasterboard is attached to your ceiling, usually adding about 40mm to its depth
New technology – thin flexible coverings similar to wallpaper (usually around 10mm thick) are attached to your ceiling, providing a finish that’s often more aesthetically pleasing than standard
How it’s installed

Standard – insulated plasterboard is fitted onto 25mm thick wooden battens, attached to your ceiling, requiring the removal and re-fitting of any ceiling roses and coving
New technology – flexible insulating coverings are attached to the ceiling using a special adhesive and then rendered or covered with wallpaper or tiles to your taste

 

[Nicebutdim]

The insulation and plaster boards are up - hooray!

Tried a few screws to support the celotex as per Freddiemercurystwin's suggestion but we couldn't hold the quilt still enough as the screw went through, so it completely shredded the quilt. Considered using clout nails but couldn't get hold of any long enough to go through all of the layers (2 inch celotex, superquilt and the original plasterboards) to the joists.

Ended up fixing thin batons over the superquilt using shorter, sharp dry wall screws. The batons held the quilt taught. Then used 6 annular nails with washers over them to support each sheet of celotex. The nails didn't wander in the celotex as the screws did and the washers stoped the nails just disappearing into the soft celotex. The plaster board was then easy using long dry wall screws to properly hold it all up - the quliting didn't shred as was held tight under the batons.

Not the best use of superquilt or the most elegant of solutions but it worked and hopefully this will be the warmest room in the house come winter. Lots of lessons learned and we won't be using the quilt on the next ceiling we need to insulate!

Thanks for all of the advice and suggestions!

 

[freddiemercurystwin]

I thought the superquilt was already stapled in position before you ever lifted any celotex up there?

 

[Nicebutdim]

It was (but perhaps not tightly enough?). The staples didn't hold it still enough to prevent the foil tearing and the fleecy inner wrapping around the screws when he tired screwing up the celotex.