I am going to put a brick porch on an old house. I want the mortar to blend in with the lime mortar of the house.
I don't want to use the real M'Coy, just something that looks a similar colour.
I propose to use white cement/lime/sand and am seeking advice on the ratios.
mark
Ive used 50:50 white/lime and about 3 times as much sand as cement/lime.
Why not use lime? It'll look the same, be the same and age the same. Only downside is you need to build slower, as it takes time to strengthen. For diy work that's usually quite practical. Don't forget to match the sand.
1:1:6 is the (white) cement option, how well it'll match... shrug.NT
Do you need lime at all? Hopefully you aren't expecting your new structure to move. If you do, the cement:lime ratio should be 1:1 - many other ratios don't work.
The other thing is the sand - most builder's sand has loads of iron oxide in it (which is what makes it yellow/orange) and it will end up looking bright yellow through to dull orange regardless of any white cement/line you use. You can get better washed sand which is lighter in colour (silver sand), and you should look for that. Don't use sandpit sand - it can be too rounded off to bind well (to reduce scratching in eyes).
The sand originally used with lime mortar will not have been graded as accurately as sand is today. To match it, you should mix sharp sand with some finer sand (such as silver sand) to get a broader particle size and shape. Sharp sand also tends to have less iron oxide than builders sand, which will help avoid it being yellow/orange.
The typical soft ratio for using with a lime mortar building is 1:1:6 cement/lime/sand, but that is soft enough to eventually allow things like moss growth. As this isn't repairing a lime mortar building, I would go for something like 1:1:3 to 1:1:4, or a no lime mix 1:0:4+plasticiser.
Pretty easy to wash out the yellow (ochre rather than oxide I think). The sand settles quickly and the yellow stays suspended in the water for several minutes, so is easy to pour off
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