lime mortar

[Anonymous]

Following a helpful response on this forum re replacing some brickwork on the flank wall of a semi detached 17c. cottage which had deteriorated and leant outwards I now have another question to put before you all:- The wall in question is some 5m long and 8 courses deep onto ground which is best described as gravel. The sole plates sit on top of the 8th course. The top 3 - 4 courses are above ground. My bricklayer said he had no problem using a lime mortar. He has used soft sand and (Rugby) powdered hydrated lime probably around 3 or 4:1 . The upper courses and surplus mortar have hardened well over the two weeks. On some of the lower courses and in particular on the front corner where 6 courses were replaced the mortar is still soft. The new sole plates arrive next week and I'm quite worried as to whether the mortar is correct and or adequate. It would only take a morning to redo it if necessary. Any ideas?

 

[Anonymous]

Whilst lime mortar has to cure it also has to dry. Wet lime mortar will probably never cure. So, at this time of year itis always tricky using lime outside.
I know others have faith in hydrated lime but personally I would not use it. Give me proper putty anytime. Mike.

 

[Anonymous]

What advice does the building regs department of your local councl have? They will doubtless inspect the work, and if it's not up to scratch, insist that it is taken down and redone to their specifications.

If your mortar won't set, what's the point of it? Have you sought the advice of a structural engineer? Do even the most ardent cement-haters insist on lime below ground?

 

[Anonymous]

I wouldn't use bagged hydrated lime anyhow ...

Why cement though? It's not what would have been used originally.

 

[Anonymous]

Thanks for the response. I have no doubt that my local council would probably want a 1metre footing to comply with modern building regs! The house has stood for nearly 400 yrs with 8 courses on what would appear to be a stable base of gravel like ground with a well drained topsoil. What I am doing is, I think, repair work on an old but not listed building. If it lasts another 400 years that'll be fine. I'd like a good workable solution without resorting to the rigidity and weight of modern building techniques applied to an older but workable structure. If a portland, lime and sand mix will suffice then I will use that; however much of the advice I have received has all been lime mortar orientated hence the request to my bricklayer to use lime. I now suspect his knowledge in that department is more limited than he had indicated. Sounds like I'm back to square one, but an extra few hours redoing three courses of brickwork will save alot of problems further on, it's just a question of what mix the mortar should actually be.

 

[Anonymous]

It's very late in the year for lime - frosts and it does take time to 'cure'. Although some people do use hydrated bagged stuff, it wouldn't be my first choice, and it has to be fresh or it's useless altogether. Maybe a putty with a pozzolan, or a feebly hydraulic, may be a better bet at this time of year.

As time is so short, I would suggest a call to a lime supplier for a chat - Mike Wye or Rydale, for example - and ask what they would recommend. See also what other posters have to say later, and there is also the free SPAB helpline. You don't have to be a member.

I agree - stick to lime. Cement will cause problems in the long term. The building has been without it for 400 years!