Insulating bay window with adjacent piers

[samiebon1]

Hi all (first post), I'm looking at insulating our ground floor bay window and have scoured pages to look for a similar arrangement to ours.

The bay window has adjacent 'piers' (walls) at the end of the curve, I'm wondering whether I should/need to also strip the plaster back on these walls as well or I can just insulate the curve at the bottom of the bay.

Photo attached, many thanks in advance!

 

[JohnD]

Full-length curtains would be easier.

How old is the house, and what is the bay made of?

(Above and below the window)

Bays above ground floor may not be brick.

What is above it?

 

[^woody^]

Yes you would need to insulate up the reveals, unless you add a section of window board wide enough to disguise the step caused by the insulation.

 

[samiebon1]

Hi @JohnD house is 1907, rest of the house is solid bricks (220mm) so I assume this is the same - its brick on the outside. Above the window there's a small roof before the rest of the house, though unsure for certain the makeup of it.

@^woody^ by wide enough window board, do you mean the window sill? I had thought about just blending it in to the reveals and living with a slightly pronounced lower bay. Also was hoping to not touch the room-facing reveals as one side has the gas meter and the other the broadband/TV inlet.

Thanks both!

 

[JohnD]

Thanks

The existing plaster is likely to be thick lime. If you hack it off you could probably use insulated plasterboard of much the same thickness and it would not be noticeable. The area of brickwork is quite small on the plinths so not much benefit from going thicker.

However, IME the little roof is probably totally uninsulated, and losing much more heat through its ceiling. You might find that by lifting the floorboards in the room above you can access it enough to get your arms in. I once had a cat go in while I was working. It is rather difficult to place insulation, so this may be a case for a sack of expanded polystyrene or loose lay. Next time the roof needs retiling would be a good time to add as much insulation as you can and a permeable membrane.

Full-length curtains really would make a big difference.

BTW when the windows are set to the outer face of the wall, the wooden board in the reveal is called a window board. You probably have a stone sill on the outside. In parts of London and nearby, the window is set to the inside face of the wall, and there is no window board, but there may be a decorative moulding. This tradition dates back to 1666. Your splay windows look like that.

 

[samiebon1]

Thanks again @JohnD . We do have a stone sill outside. Our house is up in that there Manchester.

My thought was to take the plaster off, batten, insulate between, vapour layer and board. It's just the reveal bit that's stumping me. On the attached photo, I was thinking to hack plaster off below the line - below the window and on the first reveal. Does this seem wise?

 

[JohnD]

You could run an ornamental moulding to hide the join.

It won't show once you get those long curtains.