Struggling to decide lime vs cement pointing

[CharliePD]

Hi I feel a bit embarrassed coming onto this forum as my house is just an ex council house in a rough-ish area, it's not one of these lovely old historic buildings.

But I happen to know it was built in 1922, & I'm concerned about the use of modern cement mortar which is being recommended for some significant & deep repointing on my house (chimney & lower level of house around the bitumen DPC line).

I had a builder out who i trust generally - not to rip me off & to be professional, he's done other work for me that I've been happy with, & I respect him & the firm. So he was my first port of call.
He looked at the masonry & said that lime mortar isn't needed in my bricks because the bricks are hard modern bricks & therefore cement mortar will be fine, lime is only needed for old brickwork which is softer.
I'm disabled lady with a lot of health problems, not much money & even less energy, so his recommendations are appealing in many ways. I want to just 'trust the expert'.

However I've done some research online & I'm concerned about the potential both for damp internally & also damage to the masonry over time if mortar with different porosity/flexibility than the original mortar is used.
While he will guarantee his work, I dont want to end up in the future having to hold him to it if I get blown brick faces, or even worse, to be in a position with internal damp that I cant easily prove is due to the cement pointing. I just couldnt cope with it.

So now I'm not sure if I'm worried for no reason (i do lean towards anxiety), or whether I need to be getting other builders out to give their opinions & if so then who on earth to contact... ???

Do you think any builder can tell by looking at the bricks, whether it's lime/cement?

Am hoping for advice, anything really, but particularly if anyone knows an expert in my area (nottinghamshire) who they could recommend to help me (builders or anyone really).
Can anyone offer any advice please. I've attached a couple of photos but i dont imagine they will help

Thanks in advance

 

[stuart45]

The general rule for repointing is to use the same mix as the original, only a touch weaker. As walls are constantly expanding and contracting a stronger mix is more likely to either crack or damage the bricks. As your wall looks like a 9 inch solid one, the joints would benefit from being more breathable.
The 1920's was a time when lime mortar was still in common use, but some builders were starting to gauge cement into the mix. Cement and sand alone makes a virtually unworkable mix.

 

[Cubist]

No need for embarrassment most her are only too happy to help. What has your builder recommended in terms of specific action rather than materials?

Your photos suggest to me that the pointing of those walls in much better condition than might be expected so I would expect your builder to only be recommending some small repairs in very specific areas where the mortar has been lost.

Regardless, it's never a good idea to use cement mortars to make such repairs as it does not bind well to extant lime based mortars and can induce future problems. If repairs are essential I would strongly recommend you follow @stuart45 's advice and insist a lime mortar issued.

If you can please share any photos of the damaged areas you are concerned about. I, for one, am not convinced that much work may be needed.

 

[CharliePD]

Your photos suggest to me that the pointing of those walls in much better condition than might be expected so I would expect your builder to only be recommending some small repairs in very specific areas where the mortar has been lost.

Hi thanks, sorry I was trying to show undamaged areas of the original mortar as i thought that'd be more helpful for seeing what the original was like. There is extensive mortar failure to one side of the chimney & around the base of the house, it's quite a mess. It's had some dodgy repairs in a few places done by my grandfather decades ago, where he just did what i think is called 'scam pointing'? with cement where it was just the very outer edge which is now mostly just falling off. I originally assumed the reason it fell off was his poor unprofessional technique but i now wonder...

So it's only on chimney & bottom areas of the house that need doing & he's planning to "rake out and replace" loose & failing mortar on chimney & around the bottom where it's loose. There are some areas with significant gaps, where the mortar has just fallen out, & to my knowledge the chimney has never had any work done on it since it was built, certainly doesnt appear to have had.

I'll put some photos of the areas that need work up as soon as i can get outside - I'm not well at the moment. But yes the area needing work is obviously in need of attention, big holes in some places so something needs doing for sure

Edited: for sense!

 

[CharliePD]

As your wall looks like a 9 inch solid one, the joints would benefit from being more breathable.

Thanks. Yes the bricks are 9" long & it's solid not cavity wall i believe (or at least thats what we were told when we looked into govt funded cavity wall insulation when that was all the rage - dodged a bullet there!) My family has lived here since the 50s.

So from what you're saying, you think lime mortar would be better even if it was cement or a cement mix originally?

 

[stuart45]

I doubt It'll be sand/cement mortar. I'll be either lime/sand or cement/lime/sand.
An NHL3.5 or 2 would probably be OK. The bricks look like pre war commons, so wouldn't need a really soft mortar.

 

[CharliePD]

Thanks Stuart.
I must confess I really dont understand all the different mixes/ratios etc. I'm an old lady & while I can grasp the general principle that bricks built with lime originally, need lime for repointing, if I'm honest beyond that it's all a bit over my head.

So if the consensus here is that standard "cement mortar" is no good for my brickwork, & that lime, in some form, or some ratio mix is needed, then I will have to source a different builder.
I definitely wouldnt feel confident enough to tell a builder what to use & to take responsibility for the choice. It would have to be something they were happy with & ideally something that they would recommend.

So my current dilemma is whether to trust the guy who says it doesn't need lime, full stop, & that cement mortar will be fine.

OR whether to find a different builder who knows more about it, someone who specialises in use of lime mortar or something, perhaps? I dont know. Would appreciate advice on that in terms of how to find someone.

The bricks look like pre war commons, so wouldn't need a really soft mortar.

This sounds similar to what he said - that they're hard bricks so dont need soft mortar, therefore standard cement mortar will be fine to use.

But it sounds like people here think thats definitely wrong then?

 

[stuart45]

Thanks Stuart.


This sounds similar to what he said - that they're hard bricks so dont need soft mortar, therefore standard cement mortar will be fine to use.

But it sounds like people here think thats definitely wrong then?

I wouldn't say he's definitely wrong. It depends on what the original mix is, and what strength of mix he intends to use. For the chimney stack a breathable mix isn't as important. You could suggest using a 6/1/1 sand/lime/cement mix as a compromise for the stack and below DPC.

 

[CharliePD]

I wouldn't say he's definitely wrong. It depends on what the original mix is, and what strength of mix he intends to use. For the chimney stack a breathable mix isn't as important. You could suggest using a 6/1/1 sand/lime/cement mix as a compromise for the stack and below DPC.

Interesting thank you. I'm a bit confused, I thought it was a hard & fast rule that if its lime mortar in the original build it must be the same or as close to it as possible, in a repointing job. Is that not the case then?

At any rate, I wont be suggesting anything myself to any builder because I'm very wary of the scenario of something going wrong - eg mortar craking failing or whatever, & them saying "well you wanted that mix"! And not having the underpinning knowledge it would be nigh on impossible for me to argue it. And I'm too ill to cope with that anyway.

I contacted a heritage buildings specialist i found online to ask a question & they offered to look at a photo & said that it's definitely lime based 'slaked quicklime & sharp yellow sand, may have cement mix but as it's going soft crumbling in places more likely just lime with a bit of coal ash or trass'.

So unless anyone here thinks its unwise, I'm going to contact the SPAB to see if they know a builder locally who is experienced in lime use.

Would it be ok to come back here to ask for a list of questions you adise me to ask them when they get here?

 

[CharliePD]

@Cubist here are some photos as promised.

A selection of photos, 1 of the chimney & the other 3 are of the base of the house, it's like it all the way around the base, worse some areas than others but almost none of it is sound up to about 2 ft high, mostly along & below, the DPC. The grey cement is just popping out/off in most places.
There have obviously been some repairs done over the yrs, with cement, which I think hasnt been helpful. But there must have been some original softening/crumbling/gaps, in order to prompt the cement repairs that were done (at least 30yrs ago).

 

[stuart45]

When it was previously repointed, the existing joints weren't raked out deeply enough.