Laying a Patio

[galaxy]

I am laying a large patio at the moment and ive run into a problem. The slabs are wobbling!

I put down a layer of hardcore and compacted it and then a layer of sharp sand. I have laid the slabs using the 5 blobs of cement method (4 corners and 1 in the middle). The first 40 or so went down Sunday. I didnt touch them yesterday. Went out today to have a look and about 75% are wobbling. The end ones can be lifted up at the edge!

Any ideas what I have done wrong?

[landie]

Could be you haven't compacted the sand well enough. To use the five spot method, the mortar needs a solid base or it will just sink when set and a load is applied. You may have been better using no mortar and using the sand as a levelling medium.

[galaxy]

Someone came and had a look today and reckons we shouldve put a cement mix into the sand to strengthen it because it is too soft and no amount of mortar will stick to it.

[dmsjps]

We were told at our local builders merchants to lay our patio on coarse sand with no mortar/cement, but then after it's all laid, use a rubber-based compacter to tap them all down (you can hire one for a day, weekend, whatever from a tool hire place), and then fill in all the cracks with fine sand. We were laying small slabs as opposed to large ones, so if yours are large, check with the hire company or your builders merchants that they're OK to compact down in this way. Our patio is perfect though, so good luck with yours.

[galaxy]

OK. Called in the reserves! And we never knew we lived opposite a retired builder who popped over after seeing slabs outside and said "I'll do it for you."

He ripped up ours, created a cement and sand base and laid about 8 to see how it went. They look far superior to our effort so I'm going to let him get on with it!

Thanks for your responses. Only 472 left to lay....