Window Cavity closed with mortar?

ravendude

Hello,
Have some windows and sliding door etc going in imminently.
A few of the reveals/opes were previously closed over with mortar. It's almost like the insulation at the end of the cavity was skimmed over with a thin layer of mortar. The ones that are like his are all very large windows and a large slider opening. These particular cavities were previously like this for the most part, but the cover of mortar was broken in places, just as part of pulling put the old windows etc.

Builder has since filled any missing sections of insulation but the mason also has patched the parts where the mortar came off.

Wondering if this is a no no with thermal bridging etc?
Should I be insisting it is all stripped off? It is a pretty thin layer to be fair and may be there to stop insulation from pouring out.
All the other windows have just the cavity which is showing the insulation, so wondering why these might be different. This section of the house was pumped with bonded bead in the past.

As I say, they were mostly like this from previous builders, just wondering if it is something to be fixed or not?

BryanF

Insulation should be continuous. Plaster on inside reveal should be maintained for air-tightness

What does you detail show?

There should be a a cavity closer around reveals stopping beads this is often a piece of PIR insulation.

ravendude

BryanF wrote: »

Insulation should be continuous. Plaster on inside reveal should be maintained for air-tightness

What does you detail show?

There should be a a cavity closer around reveals stopping beads this is often a piece of PIR insulation.

Thanks for the info.
All the cavities have insulation pir boards packed in. In most of the other window openings this is exposed. I can see the cavity packed with pir board. In these few the effectively concreted over with a thin layer of mortar, if that makes sense, so there doesn't seem to be a thermal break at the cavity as such. I know there is pir board packed behind the layer/scrub of mortar, but you cant really see it now, as the cavity is covered over with the mortar. My concern is whether the mortar over the cavity will be a thermal bridge or maybe its not really something to worry about...
The layer/scrub of mortar closing the cavity is just a few millimetres really.

The walls are stripped back to bare blocks at the moment but will be plastered with airtight plaster.

Bdjsjsjs

ravendude wrote: »

Thanks for the info.
All the cavities have insulation pir boards packed in. In most of the other window openings this is exposed. I can see the cavity packed with pir board. In these few the effectively concreted over with a thin layer of mortar, if that makes sense, so there doesn't seem to be a thermal break at the cavity as such. I know there is pir board packed behind the layer/scrub of mortar, but you cant really see it now, as the cavity is covered over with the mortar. My concern is whether the mortar over the cavity will be a thermal bridge or maybe its not really something to worry about...
The layer/scrub of mortar closing the cavity is just a few millimetres really.

The walls are stripped back to bare blocks at the moment but will be plastered with airtight plaster.

I cant advise on what is optimal here but I can say from experience that reveals can be remarkably cold. I have observed plenty of sills that are chilled to a lower temperature than the modern double glaze they hold, which is pretty remarkable given that windows are always u value weak spots. So I get the impression thermal bridging is a common problem there but perhaps other contributors could add more.

BryanF

Insulation should be continuous.

So remove skim of plaster at insulation.

Insulation should butt up to and ideally overlap the window frame.

Some set back the inner leaf to help the overlap