Having some building work - lime mortar or not?

[russ_all]

Hi all,

We're about to have some minor building work done (bricking up a window, replacing a door with a window). We're in a 1930s semi detached, and we suspect our mortar might contain lime. We've done a white vinegar test and I think it's fizzing enough to suggest it is lime.

However we've pointed this out to the builder, and they've commented that it's unlikely to be lime as our mortar joints are too wide for this. If we would like to use lime, they'd like to charge us extra.

So my questions - (1), does the mortar joint thickness mean anything re the presence of lime? (2) In a 1930s house with a cavity, North West England, is it likely to be lime mortar? (3) House has 70mm cavity filled with blown insulation, does it matter if they use lime or not for the changes?

Thanks in advance!

Russ

 

[^woody^]

My understating is that the reaction with vinegar and the type of lime used in lime mortar and the type used in cement mortar is similar but different and so it is not a reliable test.

The joint thickness is not related to the use of lime mortar

The cost difference is negligible for small works

It won't matter if cement mortar is used in this type o situation, but the mix ratio should be carefully determined so that it is not too strong and the colour matches the existing

 

[russ_all]

Thanks Woody, had a read of a few of your other replies on other topics, and you seem to seriously know your stuff - what a decent bloke you are spending your time helping us noobs!

Thanks again, have a virtual pint on me,

Russ

 

[stuart45]

The 30's was a time when a lot of builders were still using lime mortar, but gauging small amounts of cement into the mix to speed up the setting.
Mortar using only sand and cement is difficult to work with, unless plasticizer or lime is added.
You could ask him to use something like a 6/1/1 sand/hydrated lime/cement mix. The type of sand used will play a big part in the colour.