New Room Insulation

[Dereekoo]

25mm Celotex between rafter and 50mm over top before plasterboard .
Personality would have knocked it down and rebuilt , always going to be chilly in there .

Yep double glazed window U value is around 2.5 so lots of heat to be lost through the walls

 

[GrahamLinton]

25mm Celotex between rafter and 50mm over top before plasterboard .
Personality would have knocked it down and rebuilt , always going to be chilly in there .

They would have loved it to be knocked down and had a decent extention but there's no chance on their budget.
Sorry to be dense. The rafters are 70mm deep, you mention 25mm Celotex which would leave a required air gap of 45mm but then they are putting up T&G as the roofer said putting up pb would me too wavy because of the huge drop one side to the other.
How do I put 50mm over the top of the existing 25mm as I'd have to nail each T&G board into the rafters?
Hope it isn't a stupid question.

 

[foxhole]

They would have loved it to be knocked down and had a decent extention but there's no chance on their budget.
Sorry to be dense. The rafters are 70mm deep, you mention 25mm Celotex which would leave a required air gap of 45mm but then they are putting up T&G as the roofer said putting up pb would me too wavy because of the huge drop one side to the other.
How do I put 50mm over the top of the existing 25mm as I'd have to nail each T&G board into the rafters?
Hope it isn't a stupid question.

100mm nails , t&g will be just as “wavy” as plasterboard to uneven timber .

 

[Deluks]

It's a sh*tshow. What's your part in all this? Tell them to do it properly or walk away, just throwing good money after bad.

 

[GrahamLinton]

It's a sh*tshow. What's your part in all this? Tell them to do it properly or walk away, just throwing good money after bad.

It’s my sons house I am not there a lot but the roofer has been paid now and won’t return to fix snags

 

[Deluks]

An air gap between insulation and roof deck won't be of any use unless it's vented to the outside.
If you put insulation up as stated above, you will need ventilation between each rafter, which really should be cross ventilation, a vent at each end.

I don't now how handy you are, but the longer term fix here would be to strip the roof covering, raise up the front of the roof so that it's more flat than it is now. Infill between the top of the windows and the joists, maybe a very short stud wall.
Then a stick down vapour barrier on top of the roof deck, insulate on top of the deck, new roof covering (felt/rubber/fibreglass) and flashing. It will probably need the joist depth upgrading too, although you'd probably get away with glueing and screwing 2x2 to the underside of the existing joists.

As it is, you'll probably see the roof deck starting to rot within about 5 years.
If 5 years is long enough to save up for a new extension then crack on.

 

[Deluks]

the roofer has been paid now and won’t return to fix snags

No, don't get him back!

 

[GrahamLinton]

For the time being I will put some vents in the top plate to allow air flow on each rafter and drill some holes in each rafter at the top end to allow cross ventilation. How does that sound?

 

[Deluks]

It may not be enough, but it's better than nothing! The top plate above the windows may be compromised by having holes drilled in it, (the amount of holes you will need to be effective anyway)
You may not get adequate air movement.

 

[GrahamLinton]

I have added a video. Where I am concentrating on are gaps where you can see outside. He said they were supposed to be there forr airflow.
Video

 

[Deluks]

I have added a video. Where I am concentrating on are gaps where you can see outside. He said they were supposed to be there forr airflow.
Video

I doubt that, probably easier for them to just leave it like that and take the money.
If you like wasps nests it's a great feature.

 

[Deluks]

One option is to fit a vent at either end, in the triangular sections. This will add cross flow ventilation, if it's airy you will reduce condensation build up. Get the kitchen door reinstated to make it exterior to the house, and treat it like a lean to.
Block those open gaps at the front.
Insulate the roof however you please.

At the moment, with it being open to the house means that all steam from kettles, cooking etc will condense in this space.

 

[Deluks]

If you wish to keep it open to the house as it is, then you can cover the gaps at the front with stainless steel insect mesh.

Insulate as suggested, 25mm between, 50mm underneath. Making sure the gaps at the front aren't blocked, and allow air to enter above the insulation.

Then fit an abutment vent, this will require the flashing to be removed and reinstated, and the roof deck cut away from the wall by about 25mm

Sandtoft Top Abutment Ventilation System - 6mtr pack

The Sandtoft top abutment ventilation system provides a neat and discreet way of ventilating the roof space at a top abutment. The system comprises of 1m vent units that click together, fillers can then be attached to the vent units for profiled tiles. Once the vent units are fixed in place a...

www.roofingoutlet.co.uk

 

[GrahamLinton]

Thank you so much for all your work you’ve been really helpful and I really appreciate it

 

[flameport]

Whoever cobbled that roof together is a moron.
The plywood isn't fixed to the supports - yellow
The supports are not properly over the wall plate, but have had 90% of their already flimsy dimensions cut away, the tiniest of remaining slivers shoved over the wall plate and then tacked in place with a nail. (red)

Then there is the question of whether that plastic framed glazing is suitable for supporting the now significantly increased load of the timber, plywood, fake-o-tiles and whatever else is intended to be shoved on the inside.

The whole lot needs to be demolished before it falls down and kills someone.