Mortar Mix for 1930's/early 40's Ex telephone exchange

[Alex37]

Hi, first post on here

I am doing some minor repointing work and some cracked brick replacements in the late summer on a 1930's built ex telephone exchange constructed of LBC Rustics in what may be a lime mortar of sorts.

Im am trying to match the mortar but am unsure what mortar it is, It is a crumbley to the touch in the way a true lime mortar is.

May be able to post pictures later but does anyone who may have worked with similar buildings know what mortar mix they used for these buildings when they constructed, if they were a pure lime mortar or a Cement Lime and Sand.

 

[noseall]

Probably a lime based mortar.

Does it matter as long as you re-point in sympathy with the building? You just need to make a note of your (gauged) mix so that you end up with a uniform finish.

 

[SFK]

If it is lime mortar there are companies who will match the colour for you.
I have used www.lime-mortars.co.uk
My only sadness was seeing the delivery guy having to carry the heavy box containing the sand and mortar.
SFK

 

[Alex37]

Thanks for the reply guys, I have Attached some pictures of the mortar in question to match to a reasonable degree for some repair work in the summer.

Any thoughts to what it might be (see pics) and what is the most suitable mortar for this.

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• Alex37
• 16 May 2015
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• Alex37
• 16 May 2015
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• Alex37
• 16 May 2015
• 1

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• Alex37
• 16 May 2015
• 1

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• Alex37
• 16 May 2015
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• Alex37
• 16 May 2015
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[SFK]

I think that looks like Sharp Sand cement based mortar. But I am not sure.

In my house I have builders sand lime mortar (soft and can scratch out with screwdriver and drops as sand), builders sand cement mortar (hard, but can scratch out slowly using screwdriver, and sharp sand cement mortar pointing (difficult to make scratch mark).

So looking at your brcks this looks pointed in cement based material (my old lime mortar does not show the sharp marks from the pointing tools). The coarse mixture of sand grades suggests it is not builders sand. So my suggestion above.

My question is how hard is that sample you have pulled out? Do you have to snap it or does it easily break into two.

All please shoot me down if my guess is wrong as I only have dig experience from one house.

Sfk

 

[Alex37]

The little chunk of mortar that I prized out was underneath a brick that had cracked adjacent to gable end. Similar situation diagonaly opposite at the other end.

The weathred Mortar that I raked out when I did some pointing that was badly needed was quite soft and not hard. The chunk I pulled out is quite hard in the sense I would need to apply a lot of presure to break it in half.

Attached Picture below showing more weathred Mortar above a DPC Joint to be repointed in the matching mortar.

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• Alex37
• 16 May 2015
• 1

This weathred mortar is quite soft.^

 

[SFK]

Uhm... I am worried that I am giving poor advice. On my phone the mortar keeps looking different. Perhaps like me you have lime mortar with cement pointing?? (Which others suggest is a bad idea). Sorry to say, but I feel I should admit to my ignorance, as suggest others should comment, or you send a sample to the web site (or similar) and get them to recommend a mix (which is what they did for me).

Sfk

 

[Alex37]

Restoration can be a mind boggling task and alot of effort but worth it in the end if done sympathetically. Thanks for your suggestions SFK all usefull. I will probably next week send the pictures over to some Lime Mortar companies and ask for a recomended mix.

If anyone else here has suggestions then please drop them by