suitable mortar?

[Robbox]

Fitting a recessed gas box and I need to fill in around with some mortar to match the house pointing.
The house is constructed from Portland stone precast blocks and the builder used a very light beige mortar.

The box is almost installed, just need to squirt some foam in the sides. Then I wanted to rake out some of the foam around the sides and finish off with mortar pointing.
What about local builders sand, hydrated lime and white cement? Or sand and hydrated lime? Don't know a lot about different mortars and their qualities.
I could just trim the foam and paint, but kinda prefer to keep the sharp lines of the box.

 

[Blagard]

Getting mortar to match existing is a tricky business! - Colour can vary especially on the sand used. You can't tell its colour until it has set and dried out so mixing some as a test is one way to find out but really over the top for a little job. You need to get your hands on some light coloured sand and for such a small job you may want to consider even sand used for plastering if it is light. Certainly no problem using light coloured cement and lime. If using lime a 1:1:6 mix should be OK. Building sand has clays in it that help make it workable, plastering sand will not have clay in it (sfaik) but the lime will help.

 

[Robbox]

Getting mortar to match existing is a tricky business! - Colour can vary especially on the sand used. You can't tell its colour until it has set and dried out so mixing some as a test is one way to find out but really over the top for a little job. You need to get your hands on some light coloured sand and for such a small job you may want to consider even sand used for plastering if it is light. Certainly no problem using light coloured cement and lime. If using lime a 1:1:6 mix should be OK. Building sand has clays in it that help make it workable, plastering sand will not have clay in it (sfaik) but the lime will help.

Is foaming the gaps then raking out a bit, a good way to get the mortar to stick and fill the gap?

 

[Blagard]

Is foaming the gaps then raking out a bit, a good way to get the mortar to stick and fill the gap?

That is one way of doing it, just make sure you get it deep enough, say not less than 20mm

An alternative might be to foam it and rake out only a little say 6mm and use a coloured sealant. The sealant can be tooled to look neat. With silicone sealants you need to keep your tool wet all the time so it does not drag the sealant. However unless you have worked with silicone before I would suggest you do a practice on a throw away mock up as tooling silicone is a skill albeit a fairly easy one to get used to.

 

[Robbox]

Thanks, I think I will use mortar, feel more comfortable with that. Some of the gaps are about a cm wide. I have made up mortar that gets reasonably close to the original mortar, white cement, hydraulic lime and a local buff colour sand, 1:1:5.
Thing for me is with mortar, I can always rake it out and start again if I make a mess!