New kitchen- builder wants to leave wall unfinished behind base units is this right?

[sunglasses]

We are replacing our kitchen in same location as our previous one with a few changes. The wall behind the run of units is an outside wall- single layer of brick ( old victorian house). Kitchen is freezing and we get mice! I would like the kitchen to be as sealed up as possible to help with both these issues so we are tiling wall to wall, under the cabinets and installing underfloor heating. The wall where the old cabinets were is a mess. Exposed brick sloppily half cemented over behind where washing machine goes and plaster that is a bit cracked and broken in places near the floor. We have moved some electric sockets( above worktop level) leaving voids where the old ones were. The builder says they wouldn't usually fill these ( we are covering with a splash back ) but what if we wanted to tile? presumably wall would need to be flat so not sure why he is saying he wouldn't 'usually" fill in. Also the wall that is half cemented with brick showing- he says he can tidy up with sand and cement but not plaster because will draw in moisture. Am I being picky to want this wall to look perfect- flat with no holes even though it won't be seen? Is there any reason why it cant be?? Does anyone know more than me about such things? Please help as its really urgent

kitchen fitters are notorious for leaving an untidy shambles out of sight behind the units. It is particularly distressing when shoddy plumbing and electrics are left.

If it was my house, I would want the wall at least filled and rendered with sand and cement to reduce rain and pest entry through gaps and make it look neater and easier to keep clean or to tile. It is easier to do than plastering, which most people can't do to an acceptable standard.

I would also consider fixing 25mm rigid foam insulation slabs to the wall behind the units. Celotex, Kingspan or Knauf boards are better than plain polystyrene,

Thanks Piglet John- would fixing insulation reduce floor space ? Most of the wall has plasterboard (skimmed I think) and above the units has been painted for our previous kitchen. Would you just put insulation behind base units? If we don't have insulation would it be freezing even with underfloor heating? How would you ideally tackle the wall before installing the kitchen? You always sound very knowledgable

the board is available as thin as 25mm, so not much thicker than plaster. But it has much more insulating power than brickwork. Walls behind kitchen units can be very cold.

This sort of thing
www.wickes.co.uk/Celotex-25mm-High-Performance-Insulation-Board-1200-x-2400mm/p/190545

Thicker if you have room for it.

Great thanks. Would we need to insulate whole wall floor to ceiling? Or just behind base units? And can it go over the plaster board already there? How does it work with electrics and plumbing cables and pipes. The first bit of the electrics work has been done and plumber coming soon to do pipe work. Sorry for so many questions!

if the room has already been plastered, it's a bit late now. But it can get very cold behind the units, and the cold air will pour out over your feet when you open them. It also encourages condensation on the cold wall.

If you ever want to plasterboard a cold room, you can get a bonded board made of foam+plasterboard.

Ok so probably too late for us. Will at least make sure the wall is finished to the best it can be. Thanks for all your advice.

Not sure if this will help but I've lived in a house with a really cold kitchen, three outside walls and a concrete floor. We put loft insulation under the base units, it really made a difference.