Refurbishing gravel drives - Topping up using modern materials

[AndyMorley]

I recently re-graveled the front drive of my house. I did the job in a hurry to meet other deadlines and now have to deal with some problems.

The original surface was gravel which over time had become mixed with the underlying clay/ falling leaves to the extent that it resembled a kind of muddy concrete. Beneath this was a layer of hardcore which was clinker from the small-scale industrial forges which were a feature of the area 100 years ago. I decided not to rip it all out and replace it, but simply to improve the drainage and top up the gravel. But I did make a decision to do more than just add fresh gravel, and thought I would try using modern membrane materials. It's the correct use of those membranes that's the issue here, and the point of my question.

I installed drainage in the form of a bottle gulley to an existing RW drain, supplemented by a run of clay land-drain into the gulley.

I removed loose pebbles and debris from the compacted clay and gravel surface and laid down 2metre-wide (7') strips of black weed-guard fabric. I secured the joins with galvanised steel banding fixed in place by 6" (150mm) nails into the substrate. On top of this, I laid 2" (50mm) of 20mm gravel.

The end result is OK. It's like walking over a shingle beach. The noise gives good intruder warning and it has put an end to all former drainage problems. However, there is a downside.

Driving across it in a 4-wheel drive road vehicle is fine, but a 2-wheel drive going across it is a little bit difficult and can get slightly bogged down. Only a minor inconvenience, but noticeable. But when a truck came to tip some more gravel, when it tried to move off when empty, its wheels spun, ripping up the weed-guard fabric.

The company that supplied the gravel suggested I put hardcore underneath it. However, I'm not convinced by this suggestion as the substrate is firm and hard already, and hardcore would substantially raise the ground-level. The purpose of hardcore is mainly as a foundation and the existing hardcore foundation beneath the old gravel is fine from that point of view.

I think that a 1/2" (12mm) layer of either sharp sand or pea-shingle laid directly onto the weed-guard fabric, with a reduced thickness of the 20mm gravel – say an inch or so, might well work.

I considered nailing ACO ground-guard to the fabric as an alternative, but this has two disadvantages. First, it is expensive and second, it would prevent raking of the gravel apart from the very top layer. Raking is important to assist debris to find their way through the gravel.

Would a layer of sharp sand laid on top of the weed-guard but beneath the gravel help it to bed in and protect the fabric from wheel damage..? Has anyone ever done this..?

Thanks,

Andy Morley

[Tony McC]

Weed-guard fabric is NOT the correct geo-textile. It might be fine at preventing dandelions poking through, but it hasn't the shear strength or puncture resistance to support repeated vehicle traffickings.

Your notion to add sand and/or pea-gravel will make no discernible difference. Read the Gravels page on the main website.

[AndyMorley]

Weed-guard fabric is NOT the correct geo-textile. It might be fine at preventing dandelions poking through, but it hasn't the shear strength or puncture resistance to support repeated vehicle traffickings....Your notion to add sand and/or pea-gravel will make no discernible difference. Read the Gravels page on the main website.

Thanks Tony. I've looked at the gravels section of this site. Lots of good stuff on gravels, but nothing specific to the question I've posted here. You say weed-guard is not the correct geo-textile. What would you say IS the correct one..?

Coming back to my main question, does anyone else have any ideas..?

Andy Morley

[AndyMorley]

Update on ACO Groundguard

I've done some more research on ACO Groundguard.

http://www.acoaction.com/groundguard.html

This would normally be an ideal solution to my problem of recovering an old gravel drive, given that I want to incorporate a membrane.

The snag in my case is that I get lots of small debris such as catkins and seeds that fall from surrounding trees, ACO would not be suitable in this case as it constrains the gravel too much. I need to be able to rake the gravel from time-to-time to help these debris pass through.

As an alternative, I thought I might nail small-section tanalised batten to the fabric at a 6" gaps, and add some fines in the shape of sharp sand, both of which would help reduce the 'ball-bearing effect' mentioned in the gravel pages of this site. Any thoughts on this solution would be gratefully recieved.

Tony - I'm surprised you didn't think sharp sand would help, because on the Self-Binding Gravels section of this site it says :
" indeed, with some products, fines are actually added to improve the self-binding ability. "

Have I misunderstood something here..?

Cheers,

Andy Morley

[Tony McC]

Taking your points one at a time...

Correct geo-textile - Terram 100 or similar, TDP115, Lotrak, etc: these are construction geo-textiles NOT weed fabrics/

GroundGuard - organic matter will decay and pass through with a bit of help from a hose (if you're allowed) and the rain. As with unfettered gravel, the decmposed organic material will collect at the interface between gravel and sub-base (unless a highly permeable sub-base material has been used), but it will then be gobbled up by all sorts of nasticreechers and the end result should be no different. I've seen dozens, nay hundreds, of cell matrix pavements using a gravel and none of them are suffering because of organic material.

Nailing timber into a pavement? No way!! Nailing will pierce the fabric, compromising it efficacy and its strength, and then the grabvel will simply sink into the sand.

Fines - with some self-binding gravels, "fines" (which is not the same stuff as sharp sand) are indeed added to help stabilise the aggregate. Most self-binding gravels are limestone-based, so the fines will be limestone dust.

Sand, even grit sand, is usually quartz (or quartzitic) and this has no self-binding action. Add a sand to a gravel and it falls through to the bottom, where it may just about stabilise the lower section, but for it to stabilise the full depth of the gravel, you'd need to add so much that the finished surface would, necessarily, appear to be a mix of sand and gravel, rather than clean gravel. And such a mix would offer more obstruction to the passage of organic material than a cell matrix system.

[AndyMorley]

GroundGuard - organic matter will decay and pass through with a bit of help from a hose (if you're allowed) and the rain. As with unfettered gravel, the decmposed organic material will collect at the interface between gravel and sub-base (unless a highly permeable sub-base material has been used), but it will then be gobbled up by all sorts of nasticreechers and the end result should be no different. I've seen dozens, nay hundreds, of cell matrix pavements using a gravel and none of them are suffering because of organic material.

Tony,

Many thanks for your comprehensive reply. I'd been holding off on the Groundguard front because it's not cheap, and because you can't buy individual tiles to do a test - I've only seen it sold by the pallet. I didn't want to buy a whole pallet and then find it wasn't what I needed.

More about that in a mo, but first one last question - is there a budget cell-matrix system you can recommend, or do they all come in at about £12 squids a square metre..?

Anyway, you've convinced me that this is what I need. And, as well as that I also managed to do a sort of a test which has proved the concept...

I happened to be in our local cheap-shop yesterday. (Harrods was closed) I noticed they were selling rubber door-mats made to a similar pattern to these cell-matrix systems. OK, a rubber mat is going to be softer and more flexible than something like Groundguard, but even so after I'd bought a couple and tried them out under a section of gravel, the efect was remarkable..! I'm sure that something like that is just what I need.

Finally, I'd like to congratulate you both on this web-site and on this forum. Years ago, I used to be in the building trade for my sins, but I decided I'd had enough of real work some time ago. So now, I work in an area that's related to what you're doing here.

Part of what I've been up to lately has been advising a major international company about how to deal with Internet sites where it had been getting some flak. I don't just do the advice bit btw, I did design a training program for them, and set up an operation to start getting some of their people online and talking to customers, as you're doing here, but using public technically-orientated forums.

But my point is - they're a major international company, and they're actually in the telecoms business. You're in... ahem... rather a traditional industry, and yet you're streets ahead of anyone else I've seen in what you're doing here. Well done..!

If you don't mind, I'm going to show your site to them as an example of how do set up a technical website and forum for talking to customers. I'll email you about this separately.

[Tony McC]

I'm sure you can get the GroundGuard in specific quantities. sadly, too many suppliers in the building trade like to do what is most convenient for them rather than what is needed by the customer. It will simply be a matter of finding a different, more customer-orientated supplier.

There are many other cell systems, as you've seen, and they do tend to price their products to match those of their competitors. There are some "budget" products but I'm not sure the manufacturers would thank me for naming them as such. However, when have I ever worried about what the manufacturers think?

Look for Recyfix, Hexapath, and Ecoblock on the suppliers page.