SHEDNOTES 92: A Filofacts on Gravel

 

 

The Shed’s inclusivity policy incorporates a certain hesitation about anyone going by the name of Bunny, of any gender, but Bunny Guinness was talking our language on the subject of laying gravel at

http://www.telegraph.co.uk/gardening/gardenprojects/11500134/The-ultimate-guide-to-choosing-gravel.html/

She wrote:

In Japan, on a large commercial project, we wanted soft-looking, inexpensive paths that could cope with wheelchairs. The solution was to mix a sandy soil with a smallish particle-sized gravel and dry cement. The result was a light, sandy, firm surface that was extremely economical.

Soil and cement roads were once common in the States and at airbases in Germany. Apparently, they cultivated the soil, added water, applied the dry cement and mixed the two so they were evenly distributed. They added more water if needed and then raked it smooth. It was left to cure for seven days with no traffic. These tracks looked similar to the colour of the soil, but were hard and did not “dust”.

The Japanese method of adding the gravel gives extra texture to the mix, which looks better.

Self-binding gravels, such as Breedon gravel (from Breedon Enstone) is one of my favourites (breedon-special-aggregates.co.uk). Self-binding gravels don’t move like ordinary loose gravel; they are fine textured and have clay particles mixed with the gravel. They are spread (usually to about 50mm depth) over a hardcore base and then rolled with a heavy roller while hosing water over the roller to compact it. The water brings the clay particles to the surface and seals the top. You can ride bikes and wheelchairs over it; even your high heels won’t disappear disastrously into it. A few people don’t get on with it though. If you walk from soil to the gravel, bits of earth all over it are difficult to remove and look messy. At home when I am weeding adjacent areas I use tarpaulin to cover it. Weeds cannot be pulled out, as this breaks the surface, so glyphosate is necessary and moss killers will be needed if you don’t like the mossy look. The old-fashioned hoggin is similar, being naturally occurring well-graded gravel with clay particles. You need to find a local source, as transport is usually most of the cost.

Perhaps a more forgiving version of this is Cedec. This is a permeable product that Michael Heap (who runs CED) developed for public paths around Canary Wharf.

The client wanted a durable finish like the boules courts in France. It is a crushed aggregate with a particle size from 6mm. It packs down so it does not drift like loose gravel and is available in yellow/buff, grey and red. It can be laid on slopes up to 1:25. For steeper slopes use SuperCedec, which has a firmer surface.

Neither is suitable for regular vehicle use and the cost is from £10 per sq m.

If you have an area of tarmac or concrete you want to disguise and removing it is not an option, you can spray it with a product called Colas. A thin layer of gravel is then rolled in and the process repeated. One, two or three layers can be applied. It looks pretty much like loose gravel, although it is firm, but does not quite have the charm. You can choose the colour and type of gravel, too.

The drawbacks occur when it is used in confined spaces for vehicle use. Lots of power-steered machines will erode the gravel, exposing the black. So it needs redoing every few years if it gets heavy use. It costs from £8 per sq m.

Resin bonded gravel is gaining in popularity. It is completely immovable, being fixed with a clear resin. It can be laid on slopes, swept, washed and driven on and it stays looking pristine. Too pristine for many – it lacks the organic, relaxed feel of gravel. It is also expensive, from £30 per sq m, and needs laying on a concrete/tarmac base. Colas Leochip VLS is a version that looks more natural than many.

If you want loose gravel on a slope (not exceeding 1:10), and want to use the area for bikes, wheels and high heels, then incorporating a plastic-like mesh of polythene hexagons may be the answer. The mesh sits 40mm deep, just below the surface. Cedagravel from CED is popular and is pretty much invisible if laid properly. For those who never want to see any sign of the mesh, some routine raking would be necessary (£12.25 per sq m).

There is a fine line between gravel and sand; technically, the smallest gravel particles are 5mm – anything smaller is sand. Like gravel, sand is a natural material available in many colours and shapes of particle. Fine sand is fabulous for children’s play areas. It can be a wonderful safety surface. Coarser sands are occasionally used for paths and areas of raked surface surrounding boulders and pebbles. In grassy gardens I have seen stepping stones set winding through sand, which looked amazing. For paths, lay a 50mm-70mm depth of a coarse river sand on a bed of hardcore. It would move, your heels would sink and it would need topping up.

My favourite is loose gravel, cheap as chips, and it looks magnificent in front of a castle or cottage, but you cannot use it in certain situations, such as slopes. Many problems arise from it being laid too deep, or with rounded particles of the same size (as opposed to angular particles of different sizes) so it does not compact well.

The Shed has previously filed a Filofacts on Gravel Paths, as follows …

In Telegraph of 23.8.14, the Ask A Builder column dealt with the following question from MW of Basingstoke …
“I want to install a gravel path around my house. Owing to the confines of the area, and the fact that it may be too expensive to pave, the gravel will be right up against the house. I’m making sure not to raise the level of the path above the damp-proof course (DPC), but how much lower should it be?”
Telegraph consultant Jeff Howell said:
“Ground levels adjacent to any building must finish at least 150mm (6in, or two brick courses) below the DPC. This is to prevent rain splashing off the ground and wetting the wall above DPC level, where it might track across and cause damp patches on the inside.
“Installing a gravel path or drive is not quite as simple as it might sound. If you just spread a load of gravel on to the ground, it might look pretty for a few months, but will soon sink into the earth, and become colonised with weeds.
“A properly constructed gravel drive or path is like an iceberg, in that 90 per cent of it is out of sight. You need to excavate and remove the topsoil, line the subsoil with a geotextile, then lay and compact hardcore. Follow this with a layer of compacted “hoggin” – compacted clay, gravel and sand. This is then sprayed with hot bitumen, and has a layer of pea shingle rolled into it. The final “wearing surface” of pea shingle is spread on top of this. So your finished gravel path is actually only two stones deep – one stuck into the bitumen, the other floating on top of it.
“Don’t forget that a gravel path also needs edge restraint – timber, brick or concrete kerbing, to stop the layers of stone and shingle escaping into the surrounding soil.
“I think you’ll find paving a lot easier and cheaper. You will still need to remove the topsoil, but you can then just line with a geotextile and bed the paving slabs on sharp sand.”

For more Jeff Howell, see http://www.askjeff.co.uk/

For more Filofacts from The Shed, see

https://hack4hire.wordpress.com/category/the-filofacts/

morelater …

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