Laying a patio - a few questions

[sifu]

Hi, can anyone here help?

I've lifted my old patio and excavated to a depth of between 150mm and 220mm. The old patio had a bedding of what I can describe as a very sandy cement mix which was boken up with a lump hammer in a few hours. The sub-base was a mixture of crushed red brick, a stoney sandy mix and, in some places, what looked like proper hardcore i.e. very tough rock. The soil is clay of which I've manged to remove all soft spots. The 20 year old patio came with the house and had lifted and sunk all over. So my questions are:

Is the uneveness of the old patio most likely to have been caused by the poor foundations, the age, or the clay soil? If it's the soil, will a good 85mm+ layer of dtp1 be sufficient?

I'm planning on using a 40mm 10:1 sand/cement mix. I don't fancy all that mixing and the time limits associated with a cement bed. Is this likely to cause problems as I notice most people here recommend a bed of cement?

Where the flags touch the house do I need to butter these edges with mortar?

If I use the 10:1 mix I've read it's best to cement to outer flags. Do I need to cement the whole flag or just the edge, and is this done whilst laying the flag or can I just squeeze some into the edges on completion?

This is my first attempt at laying a patio so I'd appreciate any advice.

 

[sifu]

does anyone have any answers to any of my questions?

Thanks.

 

[Thermo]

firstly a bed of mot type 1 100mm thick will do the job.

secondly its broken up and moved for the same reason that the one you are going to lay will. lay it on a wet bed of mortar. Its more effort but the result will be better and last a hell of a lot longer.

 

[sifu]

I've read the posts from you and wabittpoo suggesting a 4/3:2:1 mix and I've been persuaded to do the same.
How do I use the mix you suggest? I saw photos of a patio you laid in another thread and it looks great, so you obviously know what you're doing. Does the mix need any compacting? Do I spread enough mix for a few slabs, compact it, then ripple the surface to allow for consolidation, or is there no need to compact and I just lay one slab at a time? The info at 'pavingexpert' doesn't seem to cover this detail.

Thank you for your time.

 

[Thermo]

the mix is used in the same way as a bricklayer would use it, although it needs to be firmer so therefore not as wet. It depends on the size and type of slab, but basically lay a bed of the mortar over the area that the slab will be laid on. i tend to do a peak in each corner and the centre, and ripple the trowel through the rest of the bed. This gives the mortar some give when the wieght of the slab is prssed down on it. once its on tap it with a rubber mallet to get it level.

hopefully these pictures should make it a bit clearer. travertine marble..nice!

note the compacted bed of mot underneath giving a firm sub base to lay the slabs on. (stops your feet getting muddy too!)

 

[sifu]

Thermo, thank you so much!
The photos have particularly helped. As they say, a photo can speak a thousand words.
The pics look fantastic, and you're right about the Travertine marble - very nice! I was just looking at some the other day and think I'll use it when I buy my next house.
I can now order the materials and I'll post the results back on here.

Once again, thanks.

 

[Thermo]

your welcome, the bills on the way

 

[sifu]

your welcome, the bills on the way

Have i done something illegal? (Yeah, bad joke I know, but I've recently become a dad, so I've no choice now)

Seriously though, thanks. I'm making pretty good headway now.

 

[Thermo]

congratulations, post some pictures when youre done!

 

[jamie Smith]

For the record, Sifu I had similar issues with my own patio about a month ago. I listened to the thermo and the advice is sound - wet bed for you! I laid mine on a bed of compacted stone dust over my hardcore, overlain by the sharp sand/building sand/cement mixture you described and it stuck like s**t to a blanket. Of the 130 I laid, I have had to pull 5 up to re-bed them, but i'm more than happy with that and it looks great.

I did end up using a wetter mix on the edges, where the slabs sit on top of a breeze block wall, because I couldn't get them to adhere first time round, but they're solid now. Hope yours goes well.