Type 1 and dust path

PDF Print

< Back to Is it accessible?

What is it?

1.5 metre wide whin dust surface on top of a Type 1 granular sub base on geotextile in a formation tray.

type1 and dust path battleby

How does it work?

This path is made up of one layer of Type 1 granular sub base that provides a reasonably durable path for use all year around. The Type 1, a material with a good distribution of stone particle sizes down to 'fines', transfers the weight of path users across the ground, helping to make a durable path. The larger stones have interlocked to give the sub base strength. The smaller stones and fines, contained in the Type 1, have also infilled any gaps between the larger stone to help bind the material together into a strong solid mass on top of the ground. The Type 1 surface is blinded with whin dust to provide a reasonably durable surface for path users, and to transfer their weight to the sub base layer below.

What are the benefits?

Whin dust can provide a number of benefits as a path surface:

  • A reasonably smooth, durable surface on level ground with gentle path gradients that can be used by most path users.

  • A cheaper unbound surface to install than a bound surface like bitmac or asphalt.

  • A natural looking formal surface that blends in well with most landscape settings.

Is it suitable?

If you are thinking about using whin dust as a path surface, here are a few points that you need to consider:

  • Whin dust surfaces can be liable to water scouring if water is not allowed to run off the path. Good path drainage is essential, for example using camber or cross fall, but careful path edge landscaping is equally important.

  • Whin dust surfaces are not very durable on steep gradients - damage caused by water flowing down the surface is highly likely.

  • Whin dust surfaces are very susceptible to frost heave. When first laid, insufficient compaction of dust surface may hold water that can freeze, then thaw, loosening the surface which is washed off by running water. Plenty of good compaction of the surface with a heavy vibrating roller can reduce damage from frost heave.

  • Whin dust surfaces are very susceptible to wear and tear from path users. When first laid, whin dust surface can be easily marked by most users, particularly if the level of use is high or where there are steep gradients present.

  • Whin dust surfaces need frequent maintenance, particularly if the level of use it high or where there are steep gradients present.

How much will it cost?

Type 1 and dust path may cost between £20 - £35/ linear metre.

How do you install it?

Here at Battleby, the method of construction was:

  • A machine operator, using a tracked excavator, stripped turfs and topsoil from the existing surface to a width of 1500mm and depth of 150mm along the central line of the route to form a formation tray. Turfs and topsoil were set aside along the length of the route for later path edge and verge landscaping work.

formation tray battleby

type 1 on geotextile in formation tray battleby

  • At the Type 1 heap, a path worker used a tracked excavator to load a wheeled dumper. The path worker then transported the load to the start of the geotextile lined tray, and tipped the Type 1 on to the geotextile to about half the tray's depth. A path worker spread the material by rake to levels and falls that created an uncompacted stone layer suitable for running a heavy loaded dumper along. This construction method was continued along the total length of the excavated tray.

half stone infilled tray battleby

  • A path worker continued to transport Type 1 with the dumper to the end of the half stone-infilled tray to lay the final stone layer on top of the first uncompacted stone layer. Working backwards, the remaining half of the tray was infilled with Type 1 above the existing ground levels. A path worker spread the laid materials to levels and falls to form a 2% (1:50) cross fall, and then compacted the material to refusal with a ride-on vibrating roller, maintaining the cross fall, to finish the compacted sub base surface flush with existing ground levels. This construction method was continued along the total length of the half stone infilled tray, back towards the Type 1 heap.

full stone infilled tray battleby

  • Any part of the compacted sub base surface deviating from the required level or cross fall was raked off, or topped up with additional Type 1 to form the correct level and cross fall, and then re-compacted to refusal again. The compacted base surface was now ready for surfacing.

  • A path worker loaded the dumper with 6mm whin dust, and transported the load to the far end of the newly laid compacted sub base surface. Working backwards, the path worker tipped the whin dust onto the compacted sub base surface. A path worker spread the tipped whin dust over the surface to a depth of 25mm, and to levels and falls to form a 2% (1:50) cross fall, and then compacted the whin dust to refusal with a ride-on vibrating roller, maintaining the cross fall. This construction method was continued along the total length of the compacted sub base surface, back to the start of the path. That completed the surfacing work.

whin dust surface battleby

  • Path workers then formed the path edges and verges with the set-aside excavated topsoil's and turfs to ensure the compacted Type 1 granular sub base layer and whin dust surface was contained. The line of the path was defined and its appearance 'softened'. All path and landscaping works were now finished!

finished type 1 and dust path battleby

Detailed drawing - Whin dust path

If you like the look of the Type 1 and whin dust path at Battleby, as a potential path surface for your project, download the detail drawing here icon Type 1 and Whin Dust Path - Detail Drawing

For a generic standard detail drawing and specification details, download them here icon Whin Dust Path - Standard Detail Drawing & Specification Details

What variations are available?

Granite dust can be used instead of whin dust for path surfacing. Granite dust is free draining, less susceptible to frost heave and has good binding properties.

Detailed drawing - Granite dust path

For a generic standard detail drawing and specification details, download them here icon Granite Dust Path - Standard Detail Drawing & Specification Details

© 2014 Paths for All - Registered Scottish Charity No: SC025535, Company Limited by Guarantee No: 168554 inc. 19 Sept 1996 at Companies House, Edinburgh