Re-pointing a 1900-built end terrace: Lime mortar or Cement/Lime mix?

[tolzqyyj]

Hello,

I've been seeking quotes for re-pointing a gable end of a terrace built around 1900. I had read online that using a lime mortar may be much more appropriate than a cement mortar or a lime/cement mix for a house of this age.

Unfortunately it is proving extremely difficult to get any quotes at all for lime mortar. Would it be OK to use a cement/lime mix or should I keep searching for more quotes?

Many thanks.

 

[Joe Malone]

No, there is no point whatsoever in combining a cement/lime mix, doing this would destroy all the limes qualities. Builders don't like using lime mortar because it isn't as workable as sand and cement but there are builders who with experience, just shop around. In all likelihood, given the age, it will have been constructed with lime mortar so use NHL 3.5 lime mortar to repoint. If it was originally sand and cement, you'll do no harm whatsoever by using lime, whereas if it was originally lime and you choose to use sand and cement then you'll cause a number of problems.
Have a look at my blog here on the subject... http://buildingdefectanalysis.co.uk/masonry-defects/seven-properties-one-problem/

 

[stuart45]

Builders don't like using lime mortar because it isn't as workable as sand and cement.

First thing you have said that I would disagree with, but having used both types I would say that lime mortar is much more workable than OPC.
Main problem for builders is that they don't know how to mix it up properly, NHL for example needs about 20 min in the mixer and then left for 20 to fatten up.
OPC is really only workable with building sand, whereas lime can be used with sharp as well.

 

[Joe Malone]

Actually Stuart, in theory i agree, in practice I don't. You are absolutely right that lime takes longer to mix up but builders don't generally understand that and use it prematurely when it is not as workable as it should be. Part of reason they don't like using it is that they don't understand it.

 

[tolzqyyj]

Thanks for the replies. I had actually got one quote for using NHL 3.5 but sadly it was much more expensive (4000+) than the average of the numerous cement mortar quotes I've had (1250). Should I expect such a price difference? Are there any particular ways I could find appropriate builders? I keep finding specialist restoration companies that do work on huge period projects rather than a 2-bed terrace!

 

[Joe Malone]

You should be looking to pay no more than around £75 per square meter including access costs. I know this because I've just completed a tender exercise for an external lime render project.