Adding a window appeerture to a concrete block wall

[Les Symonds]

Hi...I'm about to knock through a concrete block cavity wall to add a window...where can I get info on how to finish the exposed edges of the blockwork? Issues such as how to close off the exposed cavity, where to add a dpc would be useful, as would a drawing .
Any help appreciated...thanks...Les

[Perry525]

Rather than knocking a hole through the wall, use an angle grinder with a diamond tipped disk to make a clean straight cut, after fixing a piece of wood to the wall to use as a guide.
I imagine you will be fitting a modern plastic double glazed window?
Just make sure you leave enough space round the frame to fit with expanding foam.
There is not much point in fitting an expensive window, if like so many so called professionals you make a poor job of sealing the frame to the wall. Even a small hole can strip the heat from a home.
Use polystyrene sheet to fill the cavity.
Fit one inch thick polystyrene sheet over the reveal and plaster over, this will prevent the heat loss due to conductivity between the outer and inner walls and help to prevent condensation marks on te wall.

[Les Symonds]

Mnay thanks, Perry...I had already bought the diamond tipped disc in preference to just 'knocking through'. The info about insulation was very useful.