Fitting window to new lime mortar wall

[thias]

We're thinking of replacing our current bow windows with something more traditional, narrower and taller sash. To do so we'll need to cut some of the brickwork top and bottom and infill some of the brickwork on both sides. It's a 9" solid brick wall and needs doing in lime mortar.

I know lime takes an age to dry - how soon after building the new opening can a window be installed in it?

 

[^woody^]

Next day with foam

 

[stuart45]

Which lime are you using? NHL 3.5?

 

[thias]

Which lime are you using? NHL 3.5?

Yeah, or a premixed NHL mortar like this - https://www.lime-mortars.co.uk/b2c/lime-mortar/non-hydraulic/coarse-stuff/25kg

 

[stuart45]

The one in the link is non hydraulic. This one takes longer to cure than NHL 3.5.

 

[thias]

The one in the link is non hydraulic. This one takes longer to cure than NHL 3.5.

You're right, I had a senior moment. NHL == Natural Hydraulic Lime, not Non Hydraulic Lime

We'd be using NHL 3.5

 

[stuart45]

You will probably find after about 3 days the outside of the joints are quite hard, but under the top inch or so will still be a bit softer.
I would give it at least a week, maybe 2 if it's still a bit green. Depends on how big the screws are. Frame fixings are quite big.
Forgot if you're putting a sliding sash in the fixing is different.

 

[thias]

You will probably find after about 3 days the outside of the joints are quite hard, but under the top inch or so will still be a bit softer.
I would give it at least a week, maybe 2 if it's still a bit green. Depends on how big the screws are. Frame fixings are quite big.
Forgot if you're putting a sliding sash in the fixing is different.

Yikes, 3x longer than ^woody^ 's suggestion?

I did expect next day for cement mortar and longer for lime, unfortunately.

 

[stuart45]

You would have to use your own judgement at the time. If you think it's gone off enough and you are careful after a few days you might find it's OK.
NHL goes off quite quickly when you point with it, but with building it's slower. You don't want to risk breaking the joints for the same of a bit more time.
It's worth keeping the brickwork damped down for a while, and protect it from the sun.

 

[lostinthelight]

Not possible to fix ties to the frame and build it in as you go

 

[stuart45]

Not possible to fix ties to the frame and build it in as you go

I read it as a sliding sash window, but if not building in would be the better method.

 

[^woody^]

Whilst locally, mortar may be a little soft, as a whole the wall will be restrained and supported on all sides, so generally firm. The fitting of a frame with foam should be OK to the surrounding.

But practically, you would normally build the frame in as the wall is built, and so could use frame ties.

Obviously make a judgement afterwards on using any casement for a while, but that should be ok.

 

[stuart45]

If it's a traditional sliding sash box frame you probably won't be able to use frame cramps and build it in.
You often find when building with lime you can't even do the joints for a few days, depending on the weather and type of bricks or stone used.

 

[^woody^]

Oh well, there may well be some specific options relating to the specific work then, but in principle I can't see why a frame can't be built in or fitted after with a foam and secured properly at a later date.

 

[stuart45]

Maybe he could if he's careful. He will have to use his judgement on it the next day if the frame needs to go in for security.