New Roof Covering - A couple of questions.

[Woody3]

We are just about to embark on removing lots and lots of concrete tiles from the roof and replace them with slate. I just want to clarify a couple of points:

1 - Insulation

Building control are involved and want me to insulate the roof.

It's got around 300mm of fibreglass up there already (on top of the flat part of the ceiling), but where the ceilings slopes towards the eaves, there's just a 75mm gap between the felt and the lath & plaster.

As I'll be using breathable membrane under the slates, I can get away with a 25mm air gap between the insulation and membrane in these areas. Am I ok to use normal PIR insulation or is there something special that we need to use? My CO has gone AWOL, so no help there I'm afraid and we are cracking on in the next couple of weeks.

2 - Kneelered Gable end coping stones

We have coping stones on top of one of the gable ends and they need to be taken off and rebedded. What mortar should we be using? I'm thinking NHL 5 like one would with a chimney stack is this correct? Would you also use a metal dowel to help secure them in place as I can't work out what would stop them from sliding down?


Property is GII Listed 1720's farmhouse plus labourers cottage with original oak roof structure.


Cheers!

 

[kreyszig]

Have they actually specified that you need to insulate between the rafters? I would have thought a cold roof would be acceptable as long as you have enough insulation between your ceiling joists?

 

[MatthewC]

Building control are involved and want me to insulate the roof.

I don't think that this is their call. When I did mine in 2010, you had to involve building control if you were re-doing more than 25% of a thermal element, as I recall. BC then can insist that you lay a membrane but they surely cannot insist that you insulate as well. I think you also need LBC for the membrane (which I forgot!) and especially for the insulation.

PIR insulation? Not very traditional! I used Thermafleece on the ceiling joists in the loft, and had a cold loft space.

For the gable end coping you need a galvanized bit with a right angle and (usually) a curly bit on the end and I've forgotten what it's called! Probably a "roof iron" or something similar. This is fitted under the bottom piece of ridge tile to hold it all up. Available at Travis or Wickes, I think.

I would use NHL5.

Matthew

 

[Woody3]

Thanks for the replies!

I've got LBC for the breathable membrane, just no specification for the insulation, as I was hoping that we wouldn't have to touch it, but BC won't budge! My CO has since changed - it used to be under the Borough Council, but now it's the County Council and the new chap as disappeared off the face of the Earth (won't respond/answer to phone calls/emails etc), so I'm on my own. :roll:

I'll get some bags of NHL 5 ordered and will look into the alternatives to PIR!

 

[a twig]

Building control are involved and want me to insulate the roof.

I don't think that this is their call. When I did mine in 2010, you had to involve building control if you were re-doing more than 25% of a thermal element, as I recall. BC then can insist that you lay a membrane but they surely cannot insist that you insulate as well.

Matthew

Afraid BC are well within their rights - if you are replacing more than 25% of the roof it is notifiable and they very much do have to insist on improved insulation. From here: https://www.planningportal.co.uk/info/200130/common_projects/47/roof/3

If you want to carry out repairs on or re-cover less than 25 per cent of the area of a pitch or flat roof, you will not normally need to submit a building regulations application. You will need approval, however, if:

• You are replacing/ repairing more than 25 per cent of the roof area, in which case, the roof thermal insulation would normally have to be improved.

If you are doing a cold roof, do your 300mm insulation over the main ceiling, then put as much into the eaves as you can while still leaving the requisite ventilation gap and you should be fine...

 

[Flyfisher]

When I did mine in 2010, you had to involve building control if you were re-doing more than 25% of a thermal element, as I recall. BC then can insist that you lay a membrane but they surely cannot insist that you insulate as well.

I got LBC to strip our roof and install a membrane. There was no mention of any need to involve BC so I didn't 'trouble' them. I suppose I could have argued that our roof was not a 'thermal element', given that it was open to the great outdoors in many places :wink:

But if you have BC already involved then I think you'll have to play by their rules.

 

[kreyszig]

For the gable end coping you need a galvanized bit with a right angle and (usually) a curly bit on the end and I've forgotten what it's called! Probably a "roof iron" or something similar.

That's a hip iron, if I remember rightly.