pointing slabs

[billozz]

hi guys,
ive now laid my patio and have to point the joints, a friend of mine has recently had a patio done and i noticed the other day that the jointing compo seems to be shrinking, thats the only way i can describe it, there is a very slight gap between the edge of the slabs and the compo, any reason why and how to avoid it
thanks
Bill

 

[ImayKnow]

Sounds like he had a dry mix of sand and cement brushed in, a quick way to fill the gap.

Whereas a true dry mix is not totally dry, it has enough water just to bind the sand and cement together but not enough to stain the paving stones. Then use a trowel to compact it into the gap and smooth off. It's a slow process mind you.

 

[billozz]

Sounds like he had a dry mix of sand and cement brushed in, a quick way to fill the gap.

Whereas a true dry mix is not totally dry, it has enough water just to bind the sand and cement together but not enough to stain the paving stones. Then use a trowel to compact it into the gap and smooth off. It's a slow process mind you.

cheers for the reply, i guess its a bit of trial and error as to how much water to add.

 

[ImayKnow]

It's not really trial and error, you add a small amount of water, mix well, and if the sand / cement don't 'just' bind, add a little more water and mix again. Keeping doing this until the mix just binds.

 

[Dextraneous]

Simple question - what sort of sand?

 

[r896neo]

Personally i use plastering sand. I find it gives a harder joint and stains less than building sand as it holds less water.