Pebble forecourt

[allidak]

Simply superb website, both content and design-I would be grateful for your advice on the best approach to this small project.

Existing:

I have a terraced house with a 4mx4m rectangular concrete/cement finish forecourt, with planting on the 3 nonhouse sides.
The existing "concrete" rectangle is in 3 segments, with straight joints (weeds),poured at different times.

The first segment is a1.2m wide footpath in a dreadful state, constructed of remnants of original clay tile, overlaid with a 25mm layer and another 12mm layer of cementitious topping (breaking up), about 75mm overall.
I can't see much base, looks like earth and a few rocks.
Condition of this footpath segment looks beyond repair and will doubtless need to be removed.
Either a new flexible sub base or new concrete solid base will need to be formed to apply new pebble finish, depending on the final spec.

The two remaining sections of existing cement forecourt ( .7m wide path adjacent to house and the remainder rectangle) are in much better condition,
apart from one big zigzag crack with weeds downthe middle (adjacent tree removed last year, slight heave).

Proposal:

I want the forecourt finish to be "pebbles" throughout.
I have a photo of a French forecourt I like which is probably both pedestrian and vehicular, although my spec is pedestrian only. The aggregate is fairly uniform in size, about the width of a finger/thumb, say about 15-20mm, some angular stones, some round in various colours, arranged in a very smooth
flat bed with minimal joints or overlaps. Probably just well compacted over many years.
I think there are also piazzas of these small pebbles around Europe, the finish is clean and colourful and just a little textural.
To keep costs down I have also considered one option of doing the proper footpath spec to the trafficked footpath segment (gate to door), and just doing a make do spec of matching pebble (preferably set) on the adjacent existing concrete, nontrafficked. Could be a few planters or pots in that zone. I do know loose pebbles on solid base are to be avoided even with infrequent traffic(apart from foxes and cats), but my gardener suggested substantial savings could be achieved, so I will ask for your opinion on that-savings may not be so great.

I intend to use timber tanalized edgings on the sides, and the natural existing minimal fall toward the road will drain the forecourt area toward the front hedge as existing. Concrete step below front gate relevelled to suit.
Please note existings levels can be raised a bit, but preferably +30mm max.

On the website the description of deco agg or the forum discussion of pebble mosaics (no pattern in my proposal) seems to best describe the clean larger aggregate appearance I am after. I don't mind a little natural instability (brush) of surface pebbles either. I did read that small stones picked up by shoes could ruin internal floors, seems another good reason for larger more stable pebbles.

Analyzing the options, a 15-25mm aggregate seems to indicate a cement bed at least to the trafficked area, whether this is arranged as one pour or two,
on existing or new concrete. However this deco washing technique sounded a little challenging for a complete novice. Your grouting spec for pebbles on dry bed sounded easier to apply and if you advise that for my forecourt please clarify spec a little more.
A Resin bed is apparently only suitable for 3mm aggregate at present, and although a new suitable resin now exists it is not yet available on the market. Perhaps I can stick loose gravel down later next year, but I don't want to wait an entire year to reinstate my forecourt.

Finally a flexible bed sounds much easier and much cheaper, but I can't figure out how to achieve the clean consistent pebbly surface, although in my photo of the French forecourt it is very wellcompacted on a flexible base. The self binding gravel which I have checked on the linked websites will be too dusty and irregular,unless 20mm aggregate is applied over the top of the small binding particles or unless some clay or binding type stone is added for the runoff (portland?).
I want variation in colour (amber, white, green/blue but an overall light shade).

Advice requested:

Which method of construction is indicated for the different segments of forecourt.
My builder is not experienced in hard landscape, but will have the necessary skills/workmanship. Sixteen sq metres is not a large area. I agreed to do the research and also source materials (SW London).
Please also advise on suitable stone. Is the Ph neutral to be avoided with timber edgings and adjacent planting? Would steel separate better? Plants will still spill over inevitably.
I am not keen on dark colours like granite etc.

Look forward to your reply and thanks again for this site including the forum. Still can't believe my luck finding this!

[Tony McC]

I'm a little confused - are you proposing what is, essentially, a cobbled surface using small 'pebbles' rather than cobbles? If so, then you have two choices: cement bound or resin bound. Despite what you say, there are resins available to bind larger aggregate, but the cost is verging on astronomical, mainly bacuse of the quantity of resin need for each square metre.

So, that leaves a cement binder, and for me, the easiest option would be an exposed concrete, using the chosen aggregate in the top layer of concrete. In effect, if using 20mm aggregate, then you;d have, say, 75mm of a standard 30N concrete immediately overlain with 40mm of a specially mixed 30N concrete incorporating the chosen agg. Once laid and levelled, this would be retarded, allowed to partially set, and then washed to remove the cement matrix.

I can't advise of what stone to use for the deco agg as I've no idea of what it is you're trying to achieve. Take a trip to somewhere like CED in Thurrock or Silverland Stone in Chertsey to see what they have that you like.

As for the edgings: why? If this is a bound surface, edgings aren't essential.

[lutonlagerlout]

i know the type of piazza vecchio you mean kate,but they were built in the days when labour was peanuts. the type i am thinking of are prevalent in the citta alta of bergamo,but i would hazard a guess that the aggregate is probably 40-80 mm flat sided pebbles
as the gaffer says resin bound aggregate, especially large aggregate is expensive,your only other choice is to bed these on a sharp sand cement mixture ,on a subbase
cheers LLL



Edited By lutonlagerlout on 1184083686

[allidak]

Many thanks for the prompt responses. You are both agreed a cementitious bedding is the affordable solution (incidentally,the resin company most often referenced
on yoursite advised me of the 3-4mm aggregate).
Since the 3 segments of forecourt have not been mentioned by either of you
I guess I will cast a new 75mm slab to the footpath section only, treat the weeds in the joints between slabs and apply the wet 40 topping over both new and existing adjacent slabs, raising the overall level by +40. I had thought the timber edgings could be temporary and permanent shuttering to protect the paving edges. Good to know it's optional in the end. I must source a suitable aggregate next. Yes it is like a miniature Sussex cobble, or flint walling in Norfolk. I still have practical questions about delivering/storing aggregate to a London front garden with 900mm gate access (bulk/bags) and time/persons needed to apply topping to 4mx4m, any inherent temporary works. My builder is experienced but not experienced in this type of work, actually not many people around are it would seem (I've asked). My builder is willing however
so any further practical tips, anticipated pitfalls on installation would be appreciated. Again thank you both for a clear direction on this,can't beat experience.
This whole site is a knockout, a work of art even! Hardly surprising everyone mentions
it.

[lutonlagerlout]

knapped flint is NOT suitable for driveways
far far too brittle and very sharp
CED are your best bet for a good range
they do 25 kg bags as well
cheers LLL

[allidak]

One final question arises. If 2/3 of the forecourt will be a dry existing concrete base for the wet deco agg topping, what slab prep do you recommend?