Will the rafters take weight of PIR and Plasterboard?

[F54Mini]

Hi

Our house has a loft conversion done in the mid 1980s by the previous owner.

At the moment the ‘ceiling’ is just 10mm polystyrene sheets which have been wallpapered over.

The room is not freezing, I guess heat rises from the house anyway but I want to use it as an office so am planning to remove the existing ceiling and re-insulate it with Celotex between the rafters (leaving an air gap) and screwing 12.5mm plasterboard to the rafters.

My concern is whether the roof will take the weight of the boards?

The celotex weights very little so my alternative is to stick some 50mm sheets over Celotex over the rafters, tape the joins and then perhaps get some white lining paper over to so I can paint it. It wont look perfect but its doesn’t need to, its never going to be used as a bedroom etc.

 

[Mr Chibs]

If you are taking down the ceiling and replacing with new boards, don’t worry about the weight, it’ll be fine.

The actual ceiling can be insulated with loft insulation from above, save the pir for the skeilings (sloped bits).
Cover with taper edged boards and you can fill the joints, it will look half decent

 

[F54Mini]

If you are taking down the ceiling and replacing with new boards, don’t worry about the weight, it’ll be fine.

The actual ceiling can be insulated with loft insulation from above, save the pir for the skeilings (sloped bits).
Cover with taper edged boards and you can fill the joints, it will look half decent

Don’t think I explained myself very well. I meant the ceiling in the loft room itself so the sloped rafters.

The floor of the loft room, so the ceiling of the upstairs bedrooms already has insulation and the loft floor is OSB.

It’s the ceiling of the actual loft itself I want to better insulate so I can use it as an office

Thanks

 

[freddiemercurystwin]

The rafters will be fine with the minor increase in weight. Was it an official loft conversion?

 

[F54Mini]

The rafters will be fine with the minor increase in weight. Was it an official loft conversion?

Looking at the plans for the extension, I am going to say no. The house was extended at the same time the conversion was done but the plans make no reference to the loft and no staircase is shown on them despite a proper staircase being there, although I doubt it’s headheight would pass requirements anyway.

I guess it could be permitted development, hence why it’s not in the plans?

Previous owner was a builder and did it all himself. Plans had to be scanned in for me to view and the writing on it is difficult to make out but I can’t see anything relating to the loft.

As you can see from the image, there is a long beam which runs left to right on the front and back which the roof sits on. There are also a couple of additional supports.

just didn’t want to add plasterboard and have the roof start to come down!
Thanks

 

[tony1851]

Was it an official loft conversion?

If it was, the inspector must have been very short-sighted when looking at the balustrade around the stairs.

@op The rafters will be fine to support the additional weight. The ceiling the builder put in will also help to stiffen the rafters.
Why put 12.5 plasterboard in? - 9.5mm will do perfectly well and be easier to fix.

 

[F54Mini]

If it was, the inspector must have been very short-sighted when looking at the balustrade around the stairs.

@op The rafters will be fine to support the additional weight. The ceiling the builder put in will also help to stiffen the rafters.
Why put 12.5 plasterboard in? - 9.5mm will do perfectly well and be easier to fix.

Thanks, the plans for the extension show the 150mm x 50mm Purlins which sit on top of the bricks either end of the room so this seems to be what is supporting the roof I think.

I would guess the loft was converted mainly for storage and to have a bit of extra room, the eaves have sliding doors to hide the storage bits. It’s handy for us as it’s a decent sized space for an office. It’s just a little chilly so I wanted to insulate it as best I can and still have it look decent, I would rather not have Zoom calls at work with foil insulation sheets in the background, hence why I wanted to stick PB on top.

Good point about the 9.5mm stuff, the rafters are at 450mm centres so should be ok for the thinner stuff.

Appreciate the help from those who replied