The Brew Cabin

Posted: **Thu Nov 11, 2004 3:54 am**

Hi Tony,

Great site, wonder if I can get some advice please?

I've an old 250yrs listed grade 2 farmhouse with a courtyard surrounded by outbuildings.
The yard is curently tarmac with duckstones under, it feels and looks like the local co-op car park.
I would like to lift the tarmac and reclaim/re-lay the duckstones to put the yard back to its former glory.
However, I'm concerned that since the yard is used for vehicle access, laying duckstones in concrete could cause the stones to work loose.
I've read somewhere that traditionally duckstones were set in clay which allowed movement and resealing of the joints. I also read on your site that you recommend in some cases sealing the joints with pitch for similar reasons, and I like the idea of using pitch to seal the surface.

My questions are these;-
Presumably I would need to prepare some sort of base that would allow the stones to be pressed into it to get the stones level, and then I would need to pour the pitch around the stones afterwards. So what sort of a base might be needed?
Also the drive is on a slope, so how can you pour pitch between the joints without it running downhill? How fast does the pitch solidify?
In your experiece, how would the pitch sealed duckstones sit with an old farmhouse that probably originally had duckstones layed in clay? (Probably a lot better than the current Tarmac, but should I be thinking of using something else to seal the joints?).

Finally, this all sounds very labour intensive, are there any top tips as to how to:-
a)Reclaim the Duckstones from under the existing tarmac.
b) Pour the pitch without it getting all over the faces of the stones.
c) Is there a quicker/cheaper/better way to re-lay the duckstones?

Thanks for any hints or tips.

Cheers

Colin Rhodes

Posted: **Fri Nov 12, 2004 7:29 pm**

Traditionally, duckstones or cobbles (NOT setts) were bedded and jointed with clay, but then, traditionally, infant mortality was 1 in 2 and we all had rickets. Clay was fine when the pavement could expect nothing more demanding than Dobbin and a hay-laden cart behind, with the occasional overweight farmer or a knight riding one of those horses with curtains (as I recently heard them described!)

Modern demands are more imposing and even a small family car exerts a lot more stresses than Dobbin or Sir Gawain would ever even imagine, and so we need modern bedding and jointing. The usual 'modern' answer is to use a cement-based solution - either mortar or concrete, and, to be fair, when done properly, these do work, but it's the 'getting them done properly' that poses the problem.

Using pitch can work, but only for the jointing. It's too soft and too fluid to be used for a bedding material. You could use summat with a bit more stiffness, such as a self-binding gravel, or even hoggin, but concrete of some form is the usal choice, 100mm of ST1 (a relatively weak concrete that used to be 1:3:6) would do the trick. The cobbles should be bedded in to around one-third depth and then use the pitch to joint them and bring its level up to around two-thirds depth.

However, as you site is on a slope, I'm not sure how practical this would be. Pitch remains fluid (technically speaking) even when cold and 'set' and so, over a period of time, it will tend to migrate downhill. If we are talking about a gentle-ish 1:12 slope, then it wouldn't be too serious, but anything steeper than around 1:8 would need to use a modified product with a higher grit content to reduce its fluidity.

Considering your other questions, reclaiming the existing cobble sis best done by digging them up and lobbing them into a rotating mixer where they can bash against each other and the sides of the drum to clean off most or the mortar and other crud. It won't bring them up like new, but it should make them more presentable.

If you do go with the pitch, getting molten pitch on the surface is no big issue as it is relatively easy to peel off any spillage, especially if the cobbles are damp-ish to start off.

And finally, the easiest way to lay cobbles is to press them into plastic concrete and then sweep over with a cementitious slurry, thereby creating a rigid pavement that may well be gleaming white (due to the cement) in its first year, but once the crud starts to accumulate again, it will calm down considerably. The key to successful use of a slurry is getting the excess off the surface as quickly as possible, and leaving the cobbles as clean as poss. This can be done in a number of ways, but I've seen very good results using a retarding agent.

It's an interesting project, and I'd love to know how you get on, but don't underestimate just how much work is involved. I would strongly recommend doing a few test panels before making a decision on just what will work best.

Posted: **Sat Nov 13, 2004 7:17 pm**

On a project a few years back we were given the spec for relaying a cobble drive by the council, due to it being in a conservation zone, definatly no cement involved here. You may find on your listed building that traditional methods are required to be used

We have usually laid into a black ash layer over a prepared mot base.

Its a matter of tightly packing the stones with their longest length vertically, using a mallet to drive them into the ash.

This obvously produces a flexible surface that over time will grow weeds etc and look really old!

As Tony says do not under estimate the time involved, in fact it has to be one of the most tedious paving methods, but results can be great to look at.

We have reclaimed the stones in the past by loading onto a mesh screeder and pressure washing before tipping into dumper set along side.

Posted: **Sun Nov 14, 2004 1:12 pm**

Funnily enough, only last Thursday I was discussing laying on a bed of ash or cinders with some interested parties looking at recreating an old sett pavement in the centre of London Village. They've been mightily unimpressed with the performance of cementitious materials for sett pavements over the last 20-odd years and are quite interested to understand how the older construction methods managed to give so many years of almost trouble free service.

Maybe we'll see a return to the flexible construction using cinder beds and pitch jointing - after all, it worked for a couple of hundred years, and then we somehow managed to convince ourselves that rigid, cement-based construction would be better!

The Brew Cabin

Duckstones and pitch - Re-laying duckstones