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

[RepairingDave]

.... 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...

You don't necessarily a weak mix, but weaker than the bricks around it as it is easier to replace the pointing than it is to replace a brick.

 

[johnny2007]

You don't necessarily a weak mix, but weaker than the bricks around it as it is easier to replace the pointing than it is to replace a brick.

Think about this: if you're repointing, surely the wall has been there a few years.
When the bricks were initially laid, they didn't do a different mix for pointing.
Besides, if there's any excessive movement, no matter what you do, bricks will crack and pointing will do as well, whether it's a soft or hard mix.
So, just do what has been done forever, 4:1 mix.
Most importantly is the preparation that counts.
Remove old mortar at least to 20mm deep.
I go 25mm.
I use a grinding disc on a 115mm grinder to remove most of it, then a Irwin mortar rake kit set at 25mm to clean it all up.
Hoover the lot and I even use compressed air for best results, but that's a bit over the top, I know.
Then dampen the area and compact the pointing properly, making sure you get a smooth finish.
Then for the next 50-100 years, depending on weather, it won't be a problem anymore.

 

[Tingly]

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.

Thankyou. But what is OPC mix?

 

[stuart45]

Ordinary Portland Cement.

 

[Tingly]

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

Yes, am getting to the point where i truly hope everything does , as it seems so complex!

 

[stuart45]

Google the NHBC mortar mix chart. It will give you the recommended mix for exposed areas, sheltered areas, below DPC and copings etc.
In recent years more work has gone into using the correct mortars for masonry, especially for really old buildings with soft brickwork and lime mortar.