Insulation advice

[simibr]

Greetings all
I stumbled across the forum earlier in the week while doing some research.

I bought a late 19th century grade 2 listed property earlier this year. Leasehold in a converted property 3 1 bed flats and my 2 bed maisonette. My bedrooms are in the roof of the property.

Due to the recent cold weather and knowing my stop cock is in the roof space, I've been investigating a little bit to see what insulation is in the roof and surrounding areas.

It's in an interesting state, so I've been looking at options available to me. I have a load pics that will show more than my limited abilities to describe.

Building was converted in 2006/7 with the roof tiles lifted (some point in the last 10 years) and a modern roofing membrane installed. There is a 50mm ish gap between the membrane and plaster. Rock wool in the eaves and also in the ridge space (barely). There is no ventilation that I can see in the eaves/soffit or at the gable ends as it's in a terrace. So I'm struggling to understand how it all works and fits together in terms of cold/hot roofs and what I could do. There is no problems with damp spots or the like. But I've only just gained access to the ridge/eaves to monitor any condensation issues up there.

It's all in a poor state as you can see, just working through my options at the moment, so any thoughts, advice, knowledge etc is great appreciated. Any questions please ask. Thanks.

I've included a bonus Video of what they hid away behind a studwall when they converted the building.

 

[malcolm]

For breathable membranes you don't need additional ventilation if the ceiling is air tight. For an old house that has been poorly converted your ceiling isn't likely to be air tight so eaves ventilation is good to have.

Insulation is very much easier to add above sloped attic ceilings while the roof is off. I've got 40mm celotex between the rafters in my roof which gives an air gap above. It needs to have no gaps to be effective so shoving bits up won't work well. It would be a shame to remove the ceiling as it looks like lime on hazel lath, but that's probably the easiest way to add insulation. For the flat bit on top 300mm rockwool is easy maintaining a gap to the felt, maybe a bit of celotex at the edges where you don't have the room.

 

[a twig]

You sure your stop cock is in the roof space? Unless you are living in the side of a hill that’s pretty unusual, more likely just to be an isolation valve

 

[Lacan07]

Not the nicest of jobs, and I know its probably quite cramped up there, but maybe I'd clear all the cr*p out and start and again, give it a good vacuum and re-lay fresh insulation to a depth of 25 - 30cm if you can. As Malcom has said I'd imagine the roof is pretty leaky ventilation wise.

Do we think that wall has been repointed? Those joints look pretty fat.

 

[simibr]

You sure your stop cock is in the roof space? Unless you are living in the side of a hill that’s pretty unusual, more likely just to be an isolation valve

It's the 'stopcock' for my water is all I can say. Looks like it comes up from the flat below.

Edit: my jaw did drop a little when I was shown how to access it.

 

[simibr]

Thankyou all, just the type of questions/information I'm after.
The place is a bit of a Hodge podge of modern plaster board and lime n reed/lath. The ceiling above the eaves is all original, the walls modern plaster board over the original in places. My initial thoughts are making a new access hatch to the eaves on both sides and clearing out the old insulation and clearing out any debris etc. Then replacing with new.

The ridge space I would look to do the same. But I have my doubts about the ceiling strength. So it will all depend on what I find up there and how delicate I am.

The slopes ceilings are a bit more problematic. As you said Malcolm I can't slide any up/down as it would be pointless. My only real avenue here is to remove the plaster and start fresh. This could also be necessary on the ceiling too if it doesn't hold up. Any modern or original plaster I remove I'd like to replace with lime based replacement. So either lath or ....... Something you guys could recommend?. On the sloped ceiling I could potentially put a small/thin amount of something between the rafters then mount more below the rafter. Losing a bit of room space but worth it.

The roof has no dedicated ventilation but feels well ventilated . The ceiling/room is definitely not air tight (can it be called airtight considering it's a breathable lime based system ?? )

Is it advisable to use some form of netting/mesh between the rafters to stop the insulation touching/breaching the air gap below the roof membrane ?.

 

[malcolm]

If you can get a board up there you can spread your weight over a few rafters while you insulate.

Woodwool board is a good base for lime plaster. But in the loft space when you aren't plastering an external wall plasterboard would work too.

You definitely don't want any insulation to touch the roof membrane as it'll pull water inside. Netting shouldn't be necessary - if the insulation doesn't touch when it is installed it'll only settle in time and won't touch later.