The Brew Cabin

Hi there. I've found this forum very informative so far. My project over the next month is to extend an area of patio. It consists of a mixture of 300x600, 450x600 & 600x600 mock riven slabs. The existing patio was (wait for it) laid using the 5 spot method onto a 6" re-inforced concrete slab. (The house builders did it - not me!) I was going to put down a compacted bedding layer only as the ground is very firm but on reflection I was wondering how likely it is that a crack will appear between the original patio and the new given the difference in foundation? Any suggestions?

The short answer is that it depends on how well you prepare your sub-base/bedding-layer. As this is a patio area, it won't be subjected to the heavy loads of a driveway and so the risk of differential settlement is drastically reduced.

You may find, in a year or two, that there is a bit of diff between the new flags and the old, but it's unlikely to be of any real significance. I think the diff in colouring/texturing/weathering between old and new will be much more dramatic than any slight diff in levels.

Thanks for that. I'll let you know in a year or so!

As far as the flags are concerned these are made locally so the texture match will be OK. It will just take time for them to weather in.

Well, the patio extension has been laid. There was quite a difference between the old and new slabs but I got out a trusty scrubbing brush and that brought the old ones back to a reasonable condition. I don't have a power washer so it seeme to be the easiest thing to do at the time.

I also made the mistake of not following your advice about the best way to cut these slabs. After an hour with a hammer and bolster,resulting in a pile of chippings and a cracked slab,I retired to the Hire Shop and invested in a diamond disc cutter for an afternoon - marvellous what you can achieve with these!

Thanks again for the good advice.

Send us some photies, Ian - I love seeing completed jobs!

Tony, got the photos, how do I send them?

Right, let's see if this works!!

I was going to keep a photogrpahic record of the whole exercise but failed miserably so there's just before and after.

I started by marking out the area and removing the turf. There's quite a run off down my garden so I ended up by putting some sub-base down to bring up the levels. In the first two pictures you can see where I've started.



I was dead lucky in one respect as I managed to match in exactly with the line of slabs running round the outside of the conservatory (the ones at a diagonal to the main area). There was a 600mm gap so I could lift those slabs and re-lay to run straight across. A picture says a thousand words and the third one shows what I mean.



I got the levels right by running a string from the surface of the existing patio and setting a strip of wood into the ground at the thickness of a slab below this level. I then filled the whole up with the bedding layer mix, laid the slabs and there you go.



I brought the level of the lawn up to the new edge by using some turf - still a little evening off to be done.




Last point, if you're wondering why there's a washing drier stuck in the middle of it, this was part of the point of the exercise, it saves tramping on wet grass/mud in the winter time (or in the summer depending on the weather!!)

(Edited by IanDB at 11:10 am on May 12, 2004)