Repointing - do I need to add lime, and if so what type?

[danlightbulb]

Hi,

Lots of conflicting information online on this topic.

I have a mid 1930s house with solid brick walls and I need to repoint. I am doing one area currently but eventually the whole house needs doing.

Sections have been done in the past (before I owned it) and it looks like they've used a standard cement & building sand mix.

Upon raking out the section Im doing currently, the original mortar is much more coarse - I would say its sharp sand not building sand. However I can't tell if it would have been lime or cement.

I am not sure what mix to use to repoint with. Im not particularly bothered with retaining originality (much of the house has been patched up with cement & sand mix and it will take me years to get round the whole house). But I just want to use a product which won't cause any further issues.

I could go with a weaker cement and building sand mix, say 5:1 or 6:1.
Or I could add hydrated lime which B&Q sell and the bag says to mix 5 or 6 building sand with 1 part cement and 1 part hydrated lime.
Or do I need an NHL hydraulic lime? If so do I also use cement here or not?

Like I said I don't need to care about authenticity, but just want to use a suitable product that I can eventually do the whole house in, a bit at a time.

Thanks

 

[opps]

A good friend of mine is pointer. Most of his work in on Victorian properties in west London. The guy's work is like a signature. Walking around Ealing, I can identify his weather struck pointing with a 90-95% success rate.

I often redecorate the exteriors that he points.

He only uses lime if the customer expressly specifies it. When he uses lime, he has to use brick acid at the end of the job to remove the smudges but warns the customer that it will (slightly) change the colour of the pointing.

Most of the properties are red rubber bricks, which are quite soft. I have seen 130 yr old properties where he used sand/cement and there is no evidence of damage to the brick faces after 30 years.

I confess, that I know little about the subject. Each of the properties have 9 inch solid walls. Most probably have gypsum plaster skims over the original lime plastered walls.