Old uninsulated roof

[leucothea]

Hi!

I was looking for some advice on insulating my roof, which I'm planning to get re-laid in the spring.

The clay tiles are at least sixty years old—perhaps a lot older—and in reasonable condition. The main roof timbers date from 1740/41.

I'm thinking about getting a waterproof membrane fitted, adding some insulation between the rafters, adding some insulation on the inside and then plastering.

I've been thinking about wood fibre board—perhaps Lime Green Warmshell—for the insulation. And lime plaster.

But there seem to be millions of options for insulation, which I was hoping someone could help me narrow down.

Any advice at all would be appreciated!

 

[Kearn]

Are you planning to replace / remove the tiles?

If not, then you don’t have too many options. Most sensible would be a vapour permeable membrane which would have to be on the underside of the commons (instead of the top) you could either have this taut then add insulation on the inner side then cover with wood wool/wood fibre boards and then lime plaster, making sure any batoning out doesn’t damage the membrane where it’s fixed which will be a challenge. However, this will make a decent dent into your internal volume for a meaningful depth of insulation.
You might get away with having the membrane loose enough to push into the gaps between the commons and use this void partially or solely for sheepswool insulation depending on depths available vs required for your usage. But you’ll need airflow under the tiles to minimise condensation.

Are the undersides of your tiles torched heavily is it a more complete lime barrier acting as a membrane?

I ask as we have exactly that, which isn’t common at all. Basically the entire roof was lathed over the top face of the commons and then lime rendered on top before the tiles went on. This means we can approach ours slightly differently as the tiles aren’t coming off and I won’t be disturbing our interesting external lime.

Some useful starting pointers here…

Rafter-level insulation

This is the installation of thermal insulation at the level of rafters – the inclined timber members that form the top of the frame supporting a pitched roof.

www.spab.org.uk

 

[leucothea]

Thank you Kearn!

Yes, that's the plan—to re-lay the tiles.

The context is that the house needs a re-render—cracking and de-bonding botch-job cement on lime rubble—and I was advised to re-lay the older half of the roof at the same time. The thought is to re-lay it with the same tiles, adding a membrane and insulation. The roof is untidy but I'm not 100% convinced it needs re-laying.

The roof is kind of weird in that it has slate on the back and tiles on the front (slate is the local material).

Anyway, the tiles look to be heavily torched, rather than laid onto lathing and lime.

It's certainly nicely breathable—there is quite a breeze through the attic on windy days!

Thanks for the link!