Patio slabs rocking

[carlbhoy]

hi guys i've just had a new build done at the beginning of the year, slabs was laid all around the house with a patio at the back, first off the slabs were rocking and I had the builder out,we agreed that they would be taken up and relaid, as of yet they have done half of it, but they have started rocking already, a friend of mine has said the mix is too dry
The problem I have and hopefully you will give me an answer is that when it rains and the slabs get wet there is no movement, but when they are dry they rock, I have been told that when water gets underneath them it acts as a suction and therfore it causes them to remain seated does this sound feasable to you guys because all the rain we have had recently they will never dry out and the builder is coming round this week with another guy ( apparently a competent slab layer) and I just know he's going to say there is nothing wrong with them,
thanks

 

[noseall]

You could park a car on the slabs we lay and they won't budge.
We solid bed the slabs on a mix of five screed sand to one cement with a shovel of soft sand to make jointing easier. The mix is like a stiff mortar but plenty workable and by no means dry.
We form a joint using the bedding mortar and the slab is rubber hammered onto the bed until it is down onto line. If the slab is placed on the bed and there is no "knockage", i.e. the slab is level with the line before being hammered down to the line, the slab is taken up and more bedding material is added.
The patio we are currently laying is 290, 600mm x 600mm slabs. We had 12 tonne of sand delivered and two tonnes of cement and are happily banging 60 slabs down per day.
And i'm knackered.

Porchpatio2

• noseall
• 15 Sep 2015

 

[noseall]

P.S. There are far too many DIY programs advising people on how to lay slabs badly.