Should you use weak sand and cement mix when pointing so it is sacrificed?

[Tingly]

Good Morning
I want to get my building in tip top condition , especially as I may put it on the market in a few years.
it is a 1947 brick built house.
It needs a bit of pointing hither and thither and a surveyor friend mentioned that its best NOT to use a 3in 1 mix, but instead, a weak mix of sand cement and possibly lime. He said mortar should be sacrificed if there is any movement on a house.
When the builder came he was surprised at this as he always felt a strong mix is a good idea, so now I am doubtful.
Can anyone give any clarification please?
Many Thanks

 

[^woody^]

Don't use that builder. A mix that is too strong will crack and can also cause the edges of the brick to erode.

The surveyor is half right, but the mortar is not sacrificial as such, but should be flexible but not "weak".

The single most important thing with pointing is that the joint is ironed smooth and well compressed so that it forms a weathering face gives it long life and performance, and that is different to the mix strength.

Normally no stronger than 4:1, and within the range of 4 to 6:1. Or with 25% lime 75% cement as the binder ratio - ie 15:3:1 sand/cement/lime

Rake out 20mm, no less.

 

[Tingly]

Thankyou so much. Thats really good information.
Just for clarification (and because i dont know much about this stuff) is 4 to 1, 4 sand, 1 cement, 1 lime?

 

[^woody^]

Yes the higher number is sand, the second cement

 

[Rodders53]

is 4 to 1, 4 sand, 1 cement, 1 lime?

To clarify what @^woody^ posted... 4 sand 1 cement = 4:1 = 4 to 1. No lime added in that mix.

With lime the suggested mix was 15 parts sand; 3 parts cement; and 1 part lime.
(?should it have been 16 sand rather than 15?)

 

[SFK]

because i dont know much about this stuff

To be extra specific, for mortar it is "builders sand" (not "sharp sand").

is 4 to 1, 4 sand, 1 cement, 1 lime?

I see 4:1 as "4 sand + 1 cement" or "3 sand + 1 lime + 1 cement"
I see "4 sand + 1 lime + 1 cement" as having a strength of 5:1.

The lime is a substitue for the sand, not the cement.

SFK

 

[^woody^]

To clarify what @^woody^ posted... 4 sand 1 cement = 4:1 = 4 to 1. No lime added in that mix.

With lime the suggested mix was 15 parts sand; 3 parts cement; and 1 part lime.
(?should it have been 16 sand rather than 15?)

I was thinking that an equivalent of 5:1 with lime would be as "strong" as a 4:1 without.

 

[^woody^]

To be extra specific, for mortar it is "builders sand" (not "sharp sand")

Well, for extra cleverness (and longevity) a mix of sharp (toughness) and soft builders (workability) would be even better.

But god knows how to work that all out as a ratio.

 

[SFK]

 

[Tingly]

Omg! Ok , for final final clarity
4 to 1 is 4 parts builders sand 1 part cement
or if you wish to use lime (not sure why you would use lime?), 3 sand 1 cement and 1 lime
is that correct?
thankyou, its done my head in and made me laugh in equal measure (1 part laugh, 1 part done my head in!)

 

[23vc]

5 sand, 1 cement, 0.3 lime. (I think).
Agree very useful info. I’ve also wondered what situation would dictate using lime or not. Guess building age has a lot to do with it, but where do you draw the line?

 

[stuart45]

Omg! Ok , for final final clarity
4 to 1 is 4 parts builders sand 1 part cement
or if you wish to use lime (not sure why you would use lime?), 3 sand 1 cement and 1 lime
is that correct?
thankyou, its done my head in and made me laugh in equal measure (1 part laugh, 1 part done my head in!)

No, it's not correct. Lime takes the place of cement, not sand. So instead of say using a 3/1 sand/OPC mix you use a 6/1/1 sand/lime/OPC mix in which the binders still cover all the sand particles without the lack of workability. Adding lime also makes the mix more flexible and less brittle.

 

[johnny2007]

Always done a 4:1 mix (building sand and cement) and all my pointing will surely see me out.

 

[StephenStephen]

This isn't complicated enough, so I'm going to ask - what kind of lime?

 

[stuart45]

When added to a cement mortar, hydrated lime is used. Hydraulic lime is used without any cement.