1:4 or 1:5

[mangosRus]

Hi Guys,

For dense block work, below and above DPC, what would be the optimal mortar mix for a single skin out-building ? I am contemplating a 1:4 or 1:5 builders sand:cement, but not entirely sure which to pick or why.

 

[23vc]

I've done 3.1 below ground and dpc, and 5.1 above for my extension concrete blockwork so hopefully no-one will say that's too far off.

 

[vinn]

3:1 sand & cement.

 

[seasickstevie]

3:1 sand & cement.

Not above dpc surely!?

 

[tomfe]

Do a 5 sand 1 cement + plasticiser or even 6:1 if you are using light blocks. Mix until nice and creamy.
Don't do 3:1 as your mortar will be harder than the blocks and you'll get cracks.
You can use 3:1 or 4:1 below dpc but I would not bother.

 

[stuart45]

NHBC mix is below DPC 4.5/0.5/1 sand/lime/OPC or 3.5/1 sand/OPC with plaz or 3/1 sand/masonry cement.
Above is 5.5/1/1 or 5.5/1 or 4.5/1 in less exposed places.