Repointing side wall

danrv

FreeBear said:

Rake out some of the mortar and pop it in a small plastic container. Pour some vinegar on - If it fizzes, it will be lime.

But a 1970s build will most likely be cement based.

If the mortar really is lime based, then replace it with a 3:1 mix of sharp sand and NHL3.5 lime. Give the bricks a good soak with water before starting and cover with hessian when you are finished.

Helpful, thanks. 

danrv

FreeBear said:

Rake out some of the mortar and pop it in a small plastic container. Pour some vinegar on - If it fizzes, it will be lime.

But a 1970s build will most likely be cement based.

Glad I checked. Raked some out properly and the vinegar fizzes when poured over.  So it’s either lime based or a mixture of cement, lime and sand.
More likely the former which explains why it hasn’t held up well to the elements. I’ll need to get some more materials. 
Got loads of this plasticiser but don’t know if this is needed if using a lime based mix.

stuart45

It's most likely something like a 6/1/1  sand/lime/cement if built in the 70's. I can't recall lime mortar being used back then. It's only really in the last 20 years that lime mortar has started becoming more popular.

danrv

stuart45 said:

It's most likely something like a 6/1/1  sand/lime/cement if built in the 70's. 

Thanks. Take it that’s NHL 3.5 type and not hydrated. 

stuart45

No, it would have been Hydrated lime. You don't mix NHL with OPC cement.
The lime was mixed in to make it more workable, although Plaz started to be used more on site around that time. It's cheaper and easier to use than lime.

danrv

stuart45 said:

No, it would have been Hydrated lime. You don't mix NHL with OPC cement.
The lime was mixed in to make it more workable, although Plaz started to be used more on site around that time. It's cheaper and easier to use than lime.

Ok thanks. Good to know.
If there is cement in the original, it’s very little. 
I did try a 5/1 sand/cement mix on another part of the wall to get an idea. Wouldn’t want to go any stronger so I think 6/1/1 as mentioned, with lime or plasticiser. 

stuart45

Sometimes the mixes were quite weak. Often caused by the hod carriers using shovel gauges to mix up. A shovel full of heaped sand can be a lot more than a shovel of cement. Also the older bags of cement in the shed could be starting to go off.

danrv

stuart45 said:

It's most likely something like a 6/1/1  sand/lime/cement if built in the 70's. I can't recall lime mortar being used back then. It's only really in the last 20 years that lime mortar has started becoming more popular.

Thanks for the help with the mortar mix.
I’ve bought a 25kg bag of hydrated lime now I know it’s part of the original mix. Bit more than I need probably. Saw a bag of sharp sand at the local DIY store and it’s a fair bit courser than builders.
The old mortar has fine sand so doubt it’s NHL 3.5 lime only. 
Invested in a brick jointer tool too.
https://www.homebase.co.uk/ragni-1-2in-x-5-8in-brick-jointer_p272840
May be able to apply and finish with it as I find the pointing trowel a bit messy for mortar application. The less on the bricks the better.
If needs be I can have a go at making the wooden application hawk. 
The raked out mortar channels are a tad shallow at 10mm so it’s more of a filling/renewing job.

stuart45

You might find a finger trowel easier to use, as a pointing trowel can take a bit of getting used to.
What sand have you got?

danrv

stuart45 said:

You might find a finger trowel easier to use, as a pointing trowel can take a bit of getting used to.
What sand have you got?

There was an Amtech tuck pointer suggested earlier. Looks similar to a finger trowel.
I have Tarmac builders sand. Red/brown colour but this goes when mixed. I’ve gone with that as it’s readily available locally.
Only other fine sand I’ve seen is kiln dried.