Just had house repointed - should mortar be cracking?

[goldeagle]

I have had one side of my house completely repointed last week, as it was in quite bad condition. I asked the tradesman to use a lime mortar as the house in an old Bath Stone building. Although he used a lime/sand mortar I believe he may also have added some cement to help it cure.

My question is - is it normal for new mortar to have lots of little cracks in? I have just been inspecting the work after 5 days and there are lots of little cracks in the mortar everywhere, almost as if it has shrunk whilst it has cured. I have put some photos below although a bit difficult to see. Should I be worried about this? Surely if there are lots of little cracks then water can get in, freeze and damage the mortar?

Thanks

Untitled

• goldeagle
• 23 Nov 2012
• 1

Untitled

• goldeagle
• 23 Nov 2012
• 1

 

[tony1851]

Not easy to see on the pics, but could be either a little too much cement in the mix, or possibly they have not wet the joints first and the mix has dried too quickly.

 

[several]

To most builders 'lime mortar' simply means Hydrated lime/Cement/Soft Sand mix 1:1:6.

I once had my chimney repointed and asked for lime mortar, this is what I got and it did crack just like the pictures you show.

A more suitable mix would be Hydraulic Lime and a well grand sharp sand(no cement). Lime needs to be kept moist to prevent it drying too quickly and the sharp sand will prevent cracks as well.

 

[goldeagle]

Thanks for the replies.

I made sure I did my research beforehand on the mortar mix - and he assured me he used 3.5NHL hydraulic lime mixed with stone sand - think the ratio was 3:1

 

[^woody^]

Lime mortar expands when wet and micro cracking is not an issue, nor will it lead to frost damage.

Adding any cement to a lime mortar wrecks its expansion properties though. It never cures, so I can't see why your builder would add cement

 

[goldeagle]

He said "adding a bit of cement will help it cure quicker". I have read through lots of reading on the net that it can be quite common to add cement to the lime morat - but as you say the moment you add cement to the mix it removes the properties of using the lime.

I did double check what the mortar mix was and was assured it was just the lime and mortar - but I did spot a bag of open cement in the garage when the work was being done so it made me wonder!

 

[HERTS P&D]

Wet the wall with the hose pipe and see what happens.

Andy

 

[stuart45]

Lime mortar suffers more from shrinkage cracking than cement mortar, but it can self heal the cracks, unlike cement mortar.
Adding cement clogs up the pores and affects the breathing qualities of lime.
If using a hydraulic lime it will harden up quicker than pure lime without using OPC anyway.