Home DIY

The gravel keeps the Sun, and its UV radiation off of the bitumen-based material that forms the (barely) waterproofing layer of your roof. Bitumen has poor UV resistance, and even the 'best' roofing felts come with only minimal guarantees.
Most gravel isn't the matt black colour of bitumen so reflects some sunlight, and absorbs/radiates the warmth from the Sun, rather than the bitumen heating up, expanding/flowing leading to thinning & holes.
The gravel also helps to displace (some) standing water from any low points.
Sounds like there is a territory-marking stand off on your roof.

Sounds as if the cats mistake it for cat litter. :)

Get up there and lay one of your own to end the turf war and mark it as your own, once and for all?

I put a couple of drops of lavender oil on my doormat, no cat poos since. Citrus peels and lion dung are also supposedly off-putting. But sprinkling some lavender oil about the place won't look bad. Remove as many cat poos as you can first, spray their areas with antibacterial spray.

Where would one procure some lion dung in south east London?

Asking for a mate...

internet

https://www.aspinallfoundation.org/port-lympne/wildlife-park/

Do they let you into the lion cage with poo bags to collect it?

I'm guessing you need a mate in his own motor who drives past the pile of poo,
and,
at a safe distance*, chucks out some whiffy carcass,
whilst you jump out the Z4 and speedily shovel up the lion poo.

(* there is no distance that is safe).

Or,
phone and ask if they 'Off Sales'?

I had already come to that conclusion - just waiting for the neighbours to go to bed and off I'll go.

So...
Am I being crazy?
Cold rooms yeah. External wall.
What's stopping me from knocking a frame together, putting insulating material (loft stuff), putting sheet of plywood over frame. Painting.
Is that mad?

You can do it. Downside is you lose useable area in the room. Rigid insulation board probably better than floppy loft stuff. You want to try and prevent water vapour getting into the frame/ onto the wall though, otherwise you will get condensation against the cold wall and hidden mould. Foil-backed insulation board is a thing intended to make vapour resistance easier. Tape the joints.

Obviously want to avoid the mould.
How easy, can a builder do it, should I get an expert insulator?

interested in finding out what you do think i need to do the same.

Google dot-and-dab internal solid wall insulation. We had our external walls lined with insulated plasterboard. I doubt it would be that hard to do DIY, though I’m sure there a tricks that’d make it easier.

With this plasterboard, hanging shelves and pictures - do you use gripit / those self screw thibgs or go straight through and into the brick?

I've done it - although my walls are cross bonded, not cavity.

I used rough sawn 2x2 for the frame, with 2 inch standoffs to the wall (because damp), fleece insulation held up by battens, and vapour panel plasterboard.

I also added airbricks through the external wall for ventilating the void behind the stud.

If your walls are cavity, and you have no damp, you probably don't need the ventilation. You should probably have a vapour membrane though, because of sweaty breathing kids.

Is there plasterboard against the wall already? If there is, you could strip that, batten the wall, and attach filed & insulated plasterboard to that.

Have used kingspan or celotex in a flat that was badly insulated and had gas supply issues so heating was an issue. Then drylined the flat.

Better to let the wall breathe than seal.

This is all super helpful, I'll have a chat with the builder when he comes around. At least I'm informed. There's no way I'd have the time/ability to do this.

Still looking for an electrician for some part p work.

Cost of this = £1500 for one room? (builder plus materials)

How much room would I lose, approx 15-30cm from the wall?

Just trying to get some background information, if I can stop throwing money out the wall I'd be happy.

Cost depends on the size of the wall.

Insulated panels are 2400 x 1200 and around £70

Tape is cheap, battening is cheap, you can get someone to skim for £100 a day

Removing old plasterboard is a massive drag, depending on your local tip's plasterboard policy

What is the outer wall made from, is it 'dead flat'? You can get insulation ready bonded to plasterboard which can be glued to a flat wall.
You're in a flat, so unlikely you can avoid thermal bridging/ cold spots (eg. If you line the wall, the floor/ceiling/other walls are still in direct contact with the cold external wall, depends how they are constructed though). So no point going super thick, in my opinion. Doing a single room is very different to, for example wrapping a house completely in external insulation. Even 50mm will make a massive difference to heat loss as well as comfort, plus board, you could lose less than 100mm from the room.
If you cannot ventilate a void (to the outside), don't have a void. Insulation as close as possible to the wall. Vapour seal between room and cold wall as much as possible.
If you don't like all this synthetic vapour barrier stuff you could go sheep's wool/wood wool and hemp render... but good luck finding a builder.