plasterboarding loft space

[john59]

I need to plasterboard my loft space, any pointers would be of help.
Best regards.
John

 

[masona]

Okay, why do you need to plasterboard the loft space ?

 

[john59]

OK thats a fair Q. basicly I plan on making it into a games room (no i'm not planning on putting a full sized snooker table up there)
so a 28" tv a carpet and a couple of bean bags so my two lads can play their play station the floor is already down and there is a light up there, I have insulated the roof next to the roofing felt with standard loft insulation(is that ok ? its a tiled sloping roof) so I need to know what kind of plasterboard i need to get.
Regards.
John

 

[masona]

I have insulated the roof next to the roofing felt with standard loft insulation(is that ok ? its a tiled sloping roof)

It is okay providing you have at least 50mm airflow at the back and roof ridge vent for air circulation. Important otherwise condensation problem.

Roofing felt > 50mm gap > 50mm insulation slab > plasterboard on a 4"x2" roof rafter.

A standard plasterboard size depending on your loft trap measurement size, I prefer to use 6' x 3' sheet which is easy to handle if you're working on your own. I would go for 9mm plasterboard and use plasterboard screws instead of nails to prevent knocking or breaking the roof tiles.

I have to ask, have you got the correct size floor joists or following building regulation plans ?

 

[mildmanneredjanitor]

I have to ask, have you got the correct size floor joists or following building regulation plans ?

Can I take a guess?

 

[masona]

Can I take a guess?

I hope you're wrong

 

[john59]

Point taken regarding building regs and the answer is no plans are being followed, but then again the shear weight of rubbish and such that accumulates in most lofts that I removed is nowhere near the weight that the floor will be under when finished. I also have to add that for some reason when they built these houses (they are the type with a flat roof over the back and front bedrooms and bathroom, dormer type) the ceiling joists are 16" centers and the total width of the area that will be used is 6'4" and directly beneath the ceiling running the lenght of the loft (from gable to next doors dividing wall) is a supporting wall so does the above info make a difference regarding putting stronger joist in place .
Best regards.
John.
PS Am I correct in saying that I should use foil backed boards?

 

[masona]

Am I correct in saying that I should use foil backed boards?

Best to, the foil backed plasterboard will give a reflecting heat in the summer and maintaining temperature in the winter.

Are the floor joists 4"x2" ?

Any chance of a picture of your floor joists ?

PS: You should really follow building regulations for safety reason such as if there a fire below how are the lads going to get out but having said that I don't know your loft layout.

 

[legs-akimbo]

Ordinary rockwool insulation in the rafter space is asking for trouble whether an air gap is left or not, unless you have very good through roof ventillation. Foil backed Kingspan or triple R is the best method, bearing in mind that even conversions with p.p are strictly not allowed the use of mineral wool insulation between rafter as it attracts damp and sweats. Also consider the fact that in the summer the roof covering of your house can reach temperatures of around 60 degrees which would be like sitting in an oven, the double foiled rigid insulation prevents this heat from penetrating, it is excellent stuff. If you have packed the insulation in tight against the underside of the roof then take it out immediately, if you leave it in and plaster over, come the winter and when the central heating warmth meets the cold damp air outside you will know exactly what I mean,,,,left unchecked it willcause untold damage.

 

[oilman]

Ordinary rockwool insulation in the rafter space is asking for trouble whether an air gap is left or not, unless you have very good through roof ventillation. Foil backed Kingspan or triple R is the best method, bearing in mind that even conversions with p.p are strictly not allowed the use of mineral wool insulation between rafter as it attracts damp and sweats. Also consider the fact that in the summer the roof covering of your house can reach temperatures of around 60 degrees which would be like sitting in an oven, the double foiled rigid insulation prevents this heat from penetrating, it is excellent stuff. If you have packed the insulation in tight against the underside of the roof then take it out immediately, if you leave it in and plaster over, come the winter and when the central heating warmth meets the cold damp air outside you will know exactly what I mean,,,,left unchecked it willcause untold damage.

I was going to quote part of this, but the whole post applies. I insulated our roof with rockwool between the rafters, up against the felt, 20 years ago. The house (original part) is 120 years old, with a tile and felt roof,The house is 3 floors, with the top floor built into the roof space. I got a council grant to do it, and a guy came round to inspect it with the comment he would be happy to see more jobs like it as most are badly done. We have no heating upstairs, and there is generally loads of ventilation around the place. Euphemistically called draughts. As far as I know there is no problem, and on the new part, the insulation is fitted behind foil backed plaster board. Again as far as I can tell there are no problems.

Is this a case of an automatic panic response to insulation, or does it only present a problem in overheated, underventilated houses?

 

[masona]

Is this a case of an automatic panic response to insulation, or does it only present a problem in overheated, underventilated houses?

I have a room in the roof and insulation on roof rafter with air-flow at back and ceiling joists insulation which you shouldn't do. You either can have roof insulated or floor joists according to building control but I never has any problem so far but having said that it's very well ventilated. In the loft area it's very draughty and you can feel the air blowing in your face, possibly the reason because I lived very near the seafront which is breezy. In all the years in the carpentry I never come across rot condensation problem in roofing but mostly I've done is floor joists rot. I would say the problem start in overheated house with poor ventilation. I never have central heating at 25 C temperature, I have it a lot lower temperature with more clothing on and feel more comfortable and maybe that help as well. Also I think a lot depends on your property location and which way it's facing.
The building control are now insisting a minimum 250mm ceiling insulation in new home which doesn't make any heating saving at all, barely noticeable. I wish I has a draughty lead windows and open fireplace, so no problem there

 

[Studders]

The building control are now insisting a minimum 250mm ceiling insulation in new home which doesn't make any heating saving at all, barely noticeable. I wish I has a draughty lead windows and open fireplace, so no problem there

250mm is just daft for this country. Do they insist on triple glazing?

PS I can let you have some draughty leaded windows, so long as you have some nice DG ones to fill the holes left behind.

 

[legs-akimbo]

Not an over reaction by any means.....I am speaking from experience oilman as I have done many a loft conversion and building control have not allowed rockwool fill (though this has not allways been the case)where I lived in Nottingham at the time and have also been in and ripped out self conversions where the rockwool has been packed in tight and boarded over to an un ventillated and fully heated roof space, the insulation was absolutely sodden throughout and only became apparent in the depths of a cold winter, to my mind any ventillation is self defeating anyway if the insulation is packed tight enough so as not to allow the air to flow freely.

 

[chappers]

have to agree you can't get enough rockwool between most rafters now to comply with u-values any way, plus it is a nightmare for trapping moisture.
You have two alternatives to insulating between rafters you either leave a 50mm air gap over your insulation and vent it to the outside or you don't and then you must use some sort of vapour barrier between the room and the insulation to prevent moist air entering the space some local authorities will allow foil backed plasterboard some insist on a plastic membrane

 

[oilman]

You have two alternatives to insulating between rafters you either leave a 50mm air gap over your insulation and vent it to the outside or you don't and then you must use some sort of vapour barrier between the room and the insulation to prevent moist air entering the space some local authorities will allow foil backed plasterboard some insist on a plastic membrane

So it looks like I'm alright then as I have foil backed plasterboard in the new part of the building. And the old part has resident gales. From this it appears It's an automatic panic response, or have I missed something?