Diy patio relaying - Method and construction

[sillysod]

Hello everyone, this is my first post so be gentle... Due to my inability to find a local contractor to relay my patio in the near future and at a reasonable price it looks like I'll have to have a go myself. The existing 30 yr.old patio consists of approx. 100 off 450x450 slabs on a dry buliding sand with some cement base. The Bradstone Cotswold Aged Riven packages I have bought to replace them have smooth sides with a slight inward taper to the top and when butt jointed, which I want, result in a gap at the top of around 3mm which I intend to fill with kiln-dried fine sand. My plan is to take approx. 35mm off the top of the existing base and replace it with a screed of sharp sand. I want to go this route as I can see me getting in to a right mess if I use mortar. I was recommended by one contractor who DID show up to use a membrane between the existing base and the screed but from what I've read on the website I don't believe it to be necessary. Am I on the right track? Thanks.

[dig dug dan]

Laying them on screed is no good, nor is kiln dried sand in the jointing gaps. Its a recipe for disaster.
yes, you are correct, the membrane is not necessary.
lay the slabs on a hardcore base on sand and cement mortar, tapped to levels, and point using easipoint or a similar product for best results

[rxbren]

You'll also want to space the slabs a bit more to allow for a decent joint width as if you but them up there won't be sufficient space for a strong joint.
As for reasonable price you tend to get what you pay for labour wise what might seem expensive now, might be cheap if you have to redo the work in a few years. Plus the prices would more than likely be for slab layer (maybe 2) and Labourer but they're is no harm habit a go yourself just give yourself a few weekends and don't rush
If you follow the guide on the main site you should be ok using a wet mix

[sillysod]

Thanks for the replies guys but I'm a little confused. This website informs me that laying on sharp sand is OK as here http://www.pavingexpert.com/layflag3.htm so what are your reasons for saying otherwise?

[lutonlagerlout]

if you read that page carefully you will see that it is a bad idea

it only really works on small unit paving and council flags

nobody worth a carrot lays slabs or flags on sand anymore!

bag of cement is a fiver,invest 40 quid and make your patio last a year or twenty

LLL

[Tony McC]

What LLL says is correct. There are special applications where we lay flasgtones on sand or grit, but for a DIYer, you are much better off using a weak-ish mortar based on sharp sand. It may sound mess, but it's actually easier and more forgiving.

In fact, that particular flagstone is intended to be laid on a mortar bed and with 8-15mm mortar joints. You could lay on coarse sand and joint with KDS, but you'll find it incredibly difficult to achieve a good standard of finsih, the flags will start to rock after a few weeks, and then, as the jointing disappears, they'll start to wander about.

[sillysod]

In fact, that particular flagstone is intended to be laid on a mortar bed and with 8-15mm mortar joints. You could lay on coarse sand and joint with KDS, as the jointing disappears, they'll start to wander about.

Actually, Bradstone's online brochure examples show the slabs with minimal gaps and as they are smooth sided with a 2 or 3 degree upwards taper I suspect they are virtually butted at the bottom. How could they then walk about? The existing patio is laid on builder's sand and hasn't moved in 30 years.

[seanandruby]

I bet the existing flags are 2" ( 50ml ) or more and there sheer weight will keep them from wandering.

[sillysod]

I bet the existing flags are 2" ( 50ml ) or more and there sheer weight will keep them from wandering.

No, they're 32mm.

[lutonlagerlout]

without the existence of a gps laser coordinate from 30 years ago,your slabs have almost certainly moved
Butt jointing is very bad practise,same as laying on sand
I have seen shocking examples of slabs and flags laid on sand not last 3 months
you have been very lucky
LLL

[Old Codger]

Sillysod, you are asking for advice and then dismissing it from landscapers that are offering constructive info in good faith.
You should never butt joint paving for varying reasons but especially when slabs will not always be dimensionally correct.
The only reason concrete slabs have a taper is to allow them to fall out of a mould easier. the taper is not there as a guide to joint width,

[Tony McC]

Actually, Bradstone's online brochure examples show the slabs with minimal gaps and as they are smooth sided with a 2 or 3 degree upwards taper I suspect they are virtually butted at the bottom. How could they then walk about? The existing patio is laid on builder's sand and hasn't moved in 30 years.

Firstly, you are misjudging the photies. They are shown as mortar jointed, so that's a minimum 6mm.

I do a lot of work with Bradstone, so I *know*, direct from the horse's mouth as it were, just how they are intended to be laid. Butt-jointing is not what they hjad in mind when designing that product.

Secondly, the sides are NOT fully tapered. There is a slight battering to ease de-moulding. This is common with many wet-cast pavings and is NOT intended as a guide to joint width.

Finally, you stated that the original patio was builder's sand with cement. Now you say it's only builder's sand and question the opinion of those of us who have been doing this for decades.

Either take our advice and enjoy your patio or opt to believe you know better than us...but when it fails, don't come back here whingeing and asking how you can bodge it up.

[sillysod]

No offense or disrespect intended. I got a quote of £1800 from Fairview Landscaping in Hitchin http://fairviewlandscaping.co.uk/ and specified butt jointing which he didn't think was an issue and they would fill the gaps with a special material - not KDS. This is WAY more than I want to spend considering the slabs only cost me £180 so it looks like it's going to have to be DIY. I will lay them on a mortar bed as advised on here but, Tony, what is the absolute MINIMUM gap I can use as I hate the look of wide gaps. What material do you advise putting in the gaps.

[lutonlagerlout]

£1800 is very reasonable for 30M2 (IIRC)
probably the best thing is if you grab a mug of tea and spend a few hours in the "how to lay a patio section of this site"
for me the best pointing material is GFTK VDW 815
this is suitable down to joints of 3mm although i prefer 10mm joints
around £60 a tub and you will need 4 ish
however bullet proof
hitchin market place is done in its big brother the 850

cheap but labour intensive option is good old sand and cement
cost you a tenner but a day or two and ruined knees
Best of luck

LLL

[sillysod]

Thanks for the advice LLL. It's around 20 sq.m. How does that jointing compare to EasyJoint http://easyjoint.eu/ which is also claimed to work down to 3mm. 3mm at the bottom of the slab is around 5mm at the top which I would much prefer the look of over wider joints. 12.5kg of EJ is £27.50.