Pointing mortar around replacement windows

[nigel57]

Hi,

I'm about to replace some softwood windows in a listed stone house and would appreciate some guidance on the most appropriate mortar to use please.

The existing windows are pointed in portland cement though the stone walls are pointed with lime mortar.

I'm guessing that I should use lime mortar but unsure what grade to use please?

Also, any handy tips about how to use the mortar gratefully appreciated.

Thanks,

Nigel.

 

[Roger H]

I've used 3 to 1 sharp sand and lime. Lime either NHL3.5, lime putty or hydrated lime, as you fancy. If there are largeer voids between frame and window (e.g. if the window reveal is splayed), add some stones to build up the junction. I confess to also having used some expanding foam on mine, although mine isn't listed. The foam is concealed inside and out in lime though, and served to securely hold the window in place while the mortar went off. It's also got a couple of metal straps between window frame and wall too.

Traditionally the outer fillet was filled with 'burnt sand mastic' - basically dry silver sand and boiled linseed oil, mixed to a stiff paste and pushed into the gaps. You can dry the sand in the oven apparently - no need to actually burn it.

 

[malcolm]

I'm far from an expert on these things. I understand the house would have been built around the windows. When changing windows I've put new sash windows in with bits of wood wedged in to hild them in place.

For pointing around the window frame in the small gaps between wood and brick I have bought some burnt sand mastic. Flexible, breathable and all that. Haven't tried it yet. Anything next to wood needs to be breathable. I was planning to use a lime/ sand mix which would probably be fine but someome more fussy than myself pointed out it would crack as the wood shrinks. Matters little as it is breathable.

 

[nigel57]

Many thanks for the comments, Nigel.