Raking out old Mortar (Brickwork pointing)

[odgeuk]

I’ve got a 1930s external garden wall which is very badly neglected. As it’s never gonna look pretty It seems like a perfect way to learn how to repoint a wall. One thing I’m concerned about though, in all the videos I’ve seen, people rake out about 20mm of the existing mortar, which usually takes them back to a decent solid part of the existing pointing, that hasn’t been exposed to the elements. With my wall, the mortar is so bad that I feel like I could keep raking and raking until I ended up coming out the other side! (It’s a two brick width wall). When should I STOP raking out? I don’t want my new mortar to struggle to bond with the old sandy/ crumbly mortar that is left in the wall.

Also concerned about all the dirt that will have built up in the gaps. Just hose and brush it I guess?

I plan to use an angle grinder with diamond mortar disc, although most of the existing mortar is so sandy now that I think a chisel would be just as effective in places.

Also wondering if this needs a lime mortar mix, or if a 5:1 Cement mix will suffice.

 

[odgeuk]

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[space junkie]

It's important not to rake out so much that any bricks are de-stabilised.

Another imortant point will be to press the new mortar in to the depth of the opening.
If you think about old stone walls built with a cob type mortar, there was no cement or lime in the mix. It was a mixture of cow dung, clay, straw etc.
So any remaining sandy type mortar will be OK when it's dried out. So don't worry too much about the mortar left in the wall.

Follow the reccomendations for the depth of raking out.
If the existing mortar is so soft, an old uselss wood chisel or similar might be preferable to an angle grinder. They are extreme tools for raking out old mortar.

It's realy your choice on mortar mix. There are recognised methods for testing whether old mortar was lime based or cement based.
This is just one example available online.

Historic Lime vs Cement Mortar: How to Know What Type of Mortar You Have - Tuck Pointing, Brick and Chimney Repair Toronto | Turnbull Masonry Ltd

In this blog, we are going to be discussing how to tell the difference between historic lime mortar and its modern-day counterpart, cement mortar.

www.turnbullmasonry.com