Existing loft conversion - fitting new insulation

Sandy7

I need to have some roof tiles replaced and possibly have the felt replaced at the same time on my Victorian house. I gather that if more than 25% of the roof covering is removed or replaced the insulation has to be upgraded to current government regulations (270mm).



I have a converted loft (converted in the mid 1990’s) and am concerned that there will not be space externally to fit the insulation (I am currently unsure of the amount of insulation). If this is the case, is the only option to remove the plasterboard from the loft and fit it this way?


Many thanks for any advice!

Inch_High_2

Solid insulation such as Kingspan or Celotex is used in loft conversions so no need to use 270mm. You will get the same insulation value from a lot thinner insulation.

Sandy7

Thanks very much, Inch High. And this will be enough for building regs?

Doozergirl

Building Control usually dictate 125mm of solid insulation between and over the rafters.

Sandy7

Brilliant, much appreciated Doozergirl! Can you think of any issues that I might have to consider or questions I should ask roofers when I start to get quotes?

In terms of building control do they inspect the roof before any work commences and then pay a visit after the work has been completed?

Doozergirl

If the roofer is able to organise all the internal works like plastering etc. You insulate from the inside usually, it's not a small job!

Building control will want to see the insulation when it's exposed. They'll want evidence of the roof being formed the correct way with breathable membrane, ventilation gaps etc. They don't come beforehand, only when there are specific they want to see.

Sandy7

Not sure it can insulated from the inside as the loft was converted in the mid 1990's so hopefully no plastering needs to be done!

I just wondered if there are any differences re-roofing a house that already has a loft conversion or anything I should check or ask roofers?

Doozergirl

Someone is probably going to have to make a call to building control to see what they'd accept. Something like tri iso super10 (or whatever is being sold now) can be applied from outside but it depends on what level of upgrade the building inspector wants to see.