Removing cement mortar before Repointing with Lime

[iang]

Hi

I’m about to start a repointing job on my old property which is a Somerset barn built originally around 1850 and renovated in the 1980s.

It’s currently pointed with cement in a raised ribbon style.

A surveyor has recommended that we repoint with lime at a low level to help the building breathe and reduce internal humidity levels.

He has also said that once we start we will probably want to finish the whole building with lime so there is a consistent look to the pointing all around the property.

Most of the building is built with lime but some of the later construction of the building (Dormer windows and single storey extension) has been made with cement so the lime pointing will only be cosmetic.

Where the cement is covering lime mortar it comes away quite easily carefully using an sds drill and chisel.

However on the newer part of the building the cement pointing is very solid. I assume the stonework has also been built with cement mortar. I'm concerned that I could cause some damage knocking it out.

What tools would you recommmend to remove this cement pointing in the newer part of the building. A cutting tool like an angle grinder perhaps?

Any general advice before I start, especially on the removal of the pointing would be very helpful.

Thanks

Ian

 

[stuart45]

Do you know what type of stone it is? Blue lias, Hamstone. Chert?

 

[iang]

Hi Stuart. The stone is Blue lias. Please see attached photo of a new section of wall.

 

[Kearn]

You need a very deft touch wielding an angle grinder otherwise the accidental damage will be worse - I believe there are more delicate weapons, but the name escapes me…

I’d be really careful with SDS too - the pinch point is where cement pointing is attached to the stone/brick and takes the edges with it - obviously far worse for bricks and removing their arises. That said, you don’t want to be delaminating the stone either.

Trick with grinding is to score a weak point along the pointing, so you can then chip away into the resulting gap, imagine splitting the the pointing into two parallel strips with a gap running along the middle. You aim for both strips to fall inwards away from the stone and force is directed in that direction.

We have a monster internal stack, sandstone and something made by the devil. SDS won’t really make a scratch easily… I may put it down the list and consider covering it. The downside is it is a ground floor fireplace wall, so moisture trap, but the reality is that I think that whole side has been rebuilt this way not just repointed, so if true I’d only be p!ssing on the shore to try and make the tide come it. If yours is the same, you have a similar quandary, so worth getting to grips with that first to make the right plan.

Hand tools - a good scutch chisel goes a long way, plus a weighty, comfortable bolster. Something pointed too, similar to your SDS attachment, but maybe sharpened.