The Brew Cabin

Posted: **Mon Jun 05, 2017 9:03 am**

I plan to replace an existing 30-40 year old patio currently paved with low quality pressure washer damaged concrete flags directly onto compacted sand/soil by a previous owner and I also plan to construct a new paved front path over an existing unpaved turfed area. In all about 60 sq meters so quite a big job for a DIYer.

I'm planning to use 22mm calibrated Indian Sandstone probably in Raj Green or similar. So basically I plan to lift up the existing flags, dig out 150mm so that I can put a proper base down. There some ants under the existing patio and I'm keen to avoid further problems.

So basically looking at the base I was thinking of using compacted MOT1 with say a 35-40mm screed bed which I was considering binding with cement in a 1:10 or 1:6 ratio. Main paving are is 9m wide x 4.5m fall so a fair bit to lay in one go.

Looking at the screeding section it suggests that a bound base is probably better for thinner flags which makes sense. It will also be useful to stop ant problems (though they could still mine the MOT I guess). So basically my preference is for a sharp sand/cement dry mix screed type base on top of MOT.

Questions
(1) Does my approach sound reasonable?
(2) Should I run a plate compactor over the sand/cement dry screed base before scraping the excess away using rails exactly as per your videos showing sand screeding?
(3) a 9m x 4.5m seems quite large for a DIYer to tackle in one go. How long would I likely have to work with the screed before it goes off or should i do it in sections. As a DIYer I can probably bide my time until the conditions are most suitable to give me the maximum time. What conditions would be best in your opinion?
(4) I am thinking of buying a cheap C60 or C40 compactor and then reselling it on ebay when I'm done. I also might want to extend my driveway slightly as a separate project so I was leaning towards a C60. Am I right in thinking that a C60 will be fine for a patio and a light use driveway/hardstanding but a C40 would only be OK for a patio?

Posted: **Mon Jun 05, 2017 4:42 pm**

no chance of a decent job laying these on a screed bed

you have to set up datums then lines and then lay each flag individually to the line

even with concrete slabs screed beds are generally rubbish,I know lads who do it and it looks shite

I dont know which page you saw this on but it wont work with indian stone

cheers LLL

Posted: **Mon Jun 05, 2017 7:02 pm**

Ok cheers LLL. Maybe I need a rethink.

I was going to buy Calibrated Indian Sandstone with a uniform depth of either 18mm or 22mm depending on the finish I go for. Basically I'm an amateur with a bit of time on my hands in the next few weeks and I was thinking calibrated paving with screed would make the job easier for me as per the comments below.

For reference the page is http://www.pavingexpert.com/stonpv01.htm in the Calibrated Paving section about half way down the page. It says:
"The advantage of calibrated stone is that it allows a screeded bed to be used rather than the more fussy and time-consuming individual bed, and so offers a faster installation .... in theory.
...
However, the less commonly noted advantage is that a screeded bed eliminates the skills required to prepare an accurate individual bed, and so, on basic, single-plane jobs, the flag-laying task is simplified."

Posted: **Tue Jun 06, 2017 5:43 pm**

calibrated generally means the importer can squeeze more meterage of stone in a crate,its not for your convenience!
IME only the germans can produce stone that is super accurate for thickness calibration
jura limestone being my all time favourite
but even with this I still lay individually to a line
I have seen a patio laid recently on a screed bed and it was a waste of money
LLL

Posted: **Wed Jun 07, 2017 6:56 am**

OK thanks for the heads up LLL. Looks like I'm going to have to learn some new skills and do it properly!

Posted: **Thu Jun 08, 2017 6:58 pm**

The quote you provide, written by me, attempts to make the point that screeding for large paving elemnts (so that's anything more than 300x300mm in plan) only really works when laying to a single plane. It cannot accommodate changes in gradient, multiple or complex falls, summaits and valleys, and the like.

Screed bedding for calibrated flagstones is best suited for simple patios laid by experienced paving installers. For DIYers, the individual bedding method, using guidelines and/or screed rails as level guides, is the better option.

Maybe I need to re-word the advice given on that page to make this clear.

Posted: **Sat Jun 10, 2017 7:50 pm**

OK thanks for looking Tony. I do have a 9m x 4.2m single gradient patio to do so it sounded suitable to me from the webpage.

I'm going to have trouble pegging the guidelines at one end though as the patio is side on to a gravelled area on top of membrane on top of compacted MOT on top of an old underground water tank infilled with building demolition rubble! Not sure how I'm gonna get pegs in that! So i might have to peg 1 flag in from the edge and eyeball level the last flags on the 4.2 edge with a plank of wood/spirit level.

Anyway I'm glad I asked the question so I will do it with pegs somehow or another rather then screed.

Posted: **Thu Jun 15, 2017 9:36 am**

Use pieces of broken flag or brick, or even pieces of sawn timber, to establish the desired level, and then fasten the string line to a HEAVY weight, such as a CMU block or a couple of bricks and sit this on top of the established level with the string coming out from underneath, so the line is between the top of the established level and the underside of the weight.

Posted: **Tue Jun 27, 2017 8:44 am**

Thanks again Tony. This site has been so useful to me over the last 15 years so thanks for all your efforts in putting the site together and also in taking the time to answer individual questions.

Materials to be ordered today and then I'll crack on with getting a decent replacement patio laid!

The Brew Cabin

Base for indian sandstone - Suitable base for indian sandstone