The Brew Cabin

Posted: **Mon Mar 26, 2007 6:05 pm**

Hi, Thanks for a great site!

I recently utilised a local builder to lay a new patio. I prepared the base, with concrete footings and appropriate edging.

The builder laid the flags on a 45mm Mortar mix base, following the guidance of this site, although the builder stated he would have dab and dobbed. (Maybe this should have worried me at the time)

The slabs have been down for 2 days and more than a 1/3 wobble when walked upon, and several of the smaller slabs can be picked off the base, without any resistance.

Having spoken with the builder, he has stated that the slabs have been walked upon which is not possible, and this is the reason for the movement. I suspect that this is not true. I have also noted that the joints have not been buttered and in several cases, a large void is visible through the joints.

Please can you advise as to the most likely cause for the slabs not setting and wobbling, and what personal actions I can take to remedy the situation, as it appears the builder will not be contributing to this effort!

Thank you for the time invested in such a fantastic site.

Gaz

Posted: **Mon Mar 26, 2007 7:36 pm**

It sounds like he has laid them on an uneven base. If he is a dab and dob man he may have struggle to lay the patio quickly enough to make any money using the dry mix.

What sort of sand did he use, by the way?

Was the sub-base well compacted?

It shouldn't matter that they are not adhered to the ground, as long as they are pointed, as the only pressure they should receive is downward pressure.

Posted: **Mon Mar 26, 2007 9:22 pm**

why if you did the base and the edgings did you not have a go at the slabbing?? you had done the hard work
it sounds like a balls up mate,any professional hardscaper (or even a 2 bob brickie like me) would not even leave 1 slab rocking,its a cardinal sin.
a mate of mine ( a wall tiler) did something similar years ago ,and when the patio slabs rocked ,he blamed the clients cat!
a patio is meant to be walked on ,so i am afraid it sounds like a rip it out and start again job
cheers LLL

Posted: **Mon Mar 26, 2007 10:29 pm**

Cheers chaps

The sub base was solid concrete, and the slabs were laid on grit sand, using I an 8:1 mix.

To be honest I thought that there is an art to laying patio, particularly riven flags, and was worth investing in getting it done professionally.

In ripping it up, should I go back down to the base or could I scrape the top 25mm off the 50mm base and start from there?

What do you think about remixing the sand? Avoiding wasting more cash ?

Thanks for your comments!

Posted: **Tue Mar 27, 2007 5:42 pm**

If it's set you might have a problem taking just some of it out. Without seeing it it's hard to judge but I would be tempted to take it back to the sub-base and start again.

The advice on Tony's pages is top-notch and in a nutshell, if you are new to it, get a bit of water in the mix so that it's a bit sticky. Lay the mix in the area for the slab and 'feather' it a little with a spade, lay the slab in the correct position and knock it down with a maul or rubber mallet using a spirit level to check your level and fall. Butter the slab if you like but a full bedding layer and proper pointing does the trick. Stay off it over night and no heavy traffic until it is pointed.

The Brew Cabin

Identification and resolution of problem - Slabs appeared not to have set?