Stone setts question

[Firesi71]

Apologies if this has been asked before but i couldnt find it ( new to site though!)
I will shortly be laying reclaimed stone setts to my driveway. Im getting someone in to dig out to 300 mm which will allow me enough depth for the base , bedding and stones which vary 6- 7 inch deep. Am i correct in thinking the bedding should be 4\1 grit sand wih a 4 inch mOt base?

Also dos the beddinG layer need a waterprrofer adding to it?

Any help is much appreciated

[Tony McC]

The best guide can be found here for rigid/bound construction.

For a driveway, I'd look for minimum 100mm of DTp1 to give a firm sub-base, then bed the setts in 75-100mm of ST1 or C7.5 concrete. You could use the 4:1 grit sand mortar if you prefer, but a concrete bulks up the bedding with gravel/coarse aggregate and can save a few quid. It also provides better support for heavier setts (and 1t 150-175mm depth, they *will* be heavy!) over the first 24 hours.

The downside is that a concrete mix is a little more awkward to, compact, more resilient, but you should soon get a 'feel' for the ideal surcharge that gives just enough upstand to allow the setts to be properly bedded-in without having the wallop them too much.

No real need for a waterproofer unless you have vulnerable sub-surface structures, such as cellars or vaults.

[Firesi71]

Thanks very much for the info.

[Firesi71]

Hi again. Can i check that the bedding layer for this driveway is correct as st1 . Is this strong enough to accommodate vehicles parking on? I've just started again now I've got some time on my hands ! I've done the first 3 rows in a 4/1 grit sand mix but remembered you mentioned about going for a cementious bedding so thought i would move to this if this is better choice as you had previously mentioned? thanks again

[Tony McC]

ST1 is what we use to be road kerbs. That should give you some idea of its resilience. Yes: a ST4 would be considerably stronger, but, in all honesty, for a residential driveway, a super-strong bed is not as critical as well-constructed jointing. Setts are what we refer to as joint-dependent paving, so the strength needs to be there....the bedding does, of course, have a role to play, and ST1 provides that and more besides.

[Firesi71]

Thanks very much. Finally im wanting to go for pitch pointing however there is a gradual slope on the drive which over 12m raises around 20 inches- Is This OK or is it likely to be a problem with it running down?

[Tony McC]

20 inches over 12 metres -strange mix of units!

That's roughly 1:24, which is a litle steep but, as long as you start at the bottom, work up and work along the transverse courses, topping them up a little at a time, you should be OK.

Be sure to use a genuine sett jointing pitch, which has been modified not to run too much on the hotter summer days. Inferior pitches and bitumens lack the fillers that keep it stiffer at warmer temperatures,s and so there are jobs where a good proportion of the pitch jointing is now in a pool at the bottom of the slope.

[Firesi71]

Apologies!! I take it 6mm limestone is adequate for the joints ir is a pea gravel a better bet?

[Tony McC]

It doesn't really matter, because the pitch acts as a binder.

Traditionally, the streetmasons used whatever was available locally, which was often a pea-type gravel from a fluvial source (river/lake/sea) or, if they had a local quary. small chippings.

Personally, I prefer angular or sub-angular chippings as they give better interlock and hold the setts firmly in place prior to the pitch being poured.

[Firesi71]

Thanks again for all your into its been invaluable. Im around 1/3 of the setts laid now and all going well. the jointing is still causing me an issue though so could do with one final piece of advice. The average slope is 1:24 however the initial 3.5 metres of the drive are steeper around 1:10, the rest being around 1:57. I have emailed colas about using cobble sett asking if it can accommodate a slope that angle however ( probably due to not many people being in ) just I've been sent the product sheet. Whats your thoughts? I would prefer the pitch over mortar otherwise a black resin style- again if i go for this what's the best option for a drive that's cost effective for 45sqm?

[Tony McC]

I always find that Jobling Purser, with their "CobbleSeal" are far more helpful than the faceless conglomerate more accustomed to dealing with Highway's Agency and Local Authorities.

As long as you take your time, and build up the pitch in layers when working on a slope, you'll be fine. Pour a little, let it cool, add a little more....and so on....

[Firesi71]

Hi again, I’ve finally finished laying all the setts which look great but am debating pitch jointing it Myself or getting someone to do it. I’m struggling with getting quotes so wonder what sort of tradespeople I should be aiming at? General driveways and tarmac people either turn it down or have never done it? Failing that doing it myself , the product sheet from jobling says it needs to be constantly mixed by a machine with an agitator which I can’t seem to hire - only a 10 gallon tar boiler seems to be available from the local hire shop? Any advice on whether I’m looking at wrong sort of tradespeople or hire etc? Thanks again

[Tony McC]

It's a dying art, I'm afraid. I trained a couple of contractors in the past 10 years, whereas, when I started serving my time 40-odd years ago, it was considered an essential, if rarely needed, skill.

While use of a mixing action boiler is definitely the best way, the cost of suck kit can only really be justified on larger commercial projects. For most small driveways, the cost of hiring a specialist boiler would be more than the cost of the pitch itself!

As those I've trained would show you, perfectly fine results are possible with a conventional 'roof boiler', and the work itself is simple. It's tiring and tedious, addmittedly, but it's not too difficult once you understand the basics and probably well within the capabilities of a competent DIYer. Always start at the bottom and work uphill; keep the hot pitch away from water; build-up in layers a litle at a time; be very, very careful as it *will* take the skin off you!