Oak setts installation guide
Natural Oak Setts Installation Guide
Natural Oak Setts are crafted from 100% hardwood timber sourced from sustainably managed forests. As with any type of paving, there are important guidelines to follow to ensure stability, slip resistance, and to maximise the lifespan of the installation.
Please note: the following information is provided as general guidance only. Each project is unique, and site-specific conditions may require alternative methods or specifications. A detailed site survey and consultation with qualified professionals should always be undertaken before installation. Allgreen cannot be held responsible for the final installation or performance of the product once installed.
Base Preparation
When preparing the base for Natural Oak Setts, it is important to remember that the quality of the base preparation directly influences the durability and appearance of the finished surface. The exact base design will depend on the intended use and load requirements — for instance, a garden path will differ significantly from a vehicular driveway, where greater load-bearing capacity is required.A properly designed and installed sub-base will distribute and transfer loads evenly, reducing movement and ensuring a long-lasting, stable surface. It is therefore essential that the sub-base construction, drainage, and bedding materials are chosen and installed according to professional advice and the specific conditions of the site.
Category 1 – Pedestrian and Light Traffic
This category includes non-load bearing paving such as garden paths and domestic traces which only receive foot traffic. A total excavation depth of 270mm is required to allow for the following base material method:
• Oak Sett - 70mm depth
•Clean 3-6mm Grit (compacted) 100mm
•Clean angular chipping 10-20mm, (compacted) 100mm
•Sub-base Geotextile fabric.
Category 2 – Light Vehicular Traffic
This category includes light vehicular traffic such as cars and medium-sized vans for access road-ways and driveways. A total excavation depth of 320mm is required to allow for the following base material method:
•Oak Sett - 100mm depth
•Clean 3-6mm Grit (compacted) 100mm
•Clean angular chipping 10-20mm (compacted)150mm
•Sub-base Geotextile fabric.
Stabilising
If stabilisation of the bedding is required (for instance due to steep gradient, weak sub-soil or high load demand), the grit bedding layer may be lightly cement-modified (e.g., hydraulic additive such as Portland cement or hydraulic lime). However this must only be undertaken with professional design input, and note that adding binding agents reduces permeability of the bedding layer. As a general guide, 125-150kg of additives should be added to every m3 of sand.
Edge Restraints
Under the traffic load, the paving is pushed sideways and requires an edge restraint to retain it to avoid loss of shape and load-bearing capacity. There are numerous edge restraint methods and some of these are as follows:
Pedestrian Use (paths, patios etc)
Use a suitable fixed edge restraint (e.g., cast concrete kerb, Oak landscape sleeper, heavy duty steel or large format stone edging) mechanically anchored into the sub-base/chippings layer. The edge restraint must be embedded into and tied into the chippings layer so that lateral movement of the setts is prevented. The edge restraint design may be less robust than vehicular installations but still must allow for full height of sub-base + bedding to be contained.
Light Traffic Use (driveways, domestic vehicles)
Edge restraints must be substantially stronger: e.g., heavy duty concrete kerb or stone edging with concrete haunching to opposing side to the oak sett area for anchoring stability. Edge restraints should continue along all edges subject to wheel loads (e.g., side edges, curb edges, driving lane interface) and integrate with drainage or channel edges to maintain structural continuity.
Drainage
Where possible, rainwater should be drained across the surface of the paving. To promote this and to avoid traffic hindrance from a layer of water on the surface of the paving, the paving should be installed on a gradient to shed water. Generally, paving is installed with a gradient sloping sideways so that the water will drain to and off the side as quickly as possible. For larger areas, such as square terraces, gullies should be installed. The surrounding paving should then slope towards the gullies or drainage channels that will then transfer the water into the drainage system.
Weathering & frost heave considerations
Oak Setts are naturally frost resistant but if the base does not drain properly, there is a risk that there will be insufficient expansion space between the joints, therefore causing the sand base to swell or rise, pushing the paving upwards. This phenomenon is known as frost heaving. Using a relatively coarse free-draining 3–6 mm grit bedding layer is beneficial in frost-prone conditions because good drainage helps reduce the risk of frost-heave — the three primary contributing factors are: (1) frost-susceptible soil, (2) a supply of water, and (3) freezing temperatures.
However, a free-draining granular bedding alone does not guarantee zero frost-heave: the sub-base and sub-soil must also be non-frost-susceptible (i.e., well drained, stable, minimal fines content) and water must not accumulate beneath the oak setts.
Pointing
Oak Setts should be installed with a minimum of 5mm and a maximum of 10mm joints. Once the Oak Setts have been installed, all left over material should be removed from the surface and 1-3mm washed grit swept into the joints before use. Do not use a hardening or curing pointing product with Oak Setts as this will not allow the natural weathering process of green timber. It is important that a loose and free draining substrate is used to allow maximum permeability and the normal movement of timber throughout its lifespan.
Finishing
Oak Setts do not require treatment and are extremely durable. In the natural weathering process, the Oak Setts will change colour from pale yellow/honey to a light grey. If a warm colour is preferred, you can dress the Oak Setts with a natural oil, such as Danish oil, which will darken the appearance. If you are unsure, please request images or samples of freshly cut and weathered material to determine the desired finish. Oak Setts are a natural hardwood and will vary in appearance. Splits and cracks may occur and this is a normal weathering process. Staining or marking as a result of contact with steel can be removed by the application of oxalic acid. Consult a specialist wood stain stockist for more details.
Maintenance & Inspection
Inspect periodically (at least annually) for any signs of movement, settlement, edge restraint displacement or drainage obstruction. Remove weeds or vegetation growing in joints or at edges which may undermine edge restraint or drainage. Ensure that falls and surface drainage outlets remain clear and effective; ponding or blocked drainage will accelerate deterioration and potential movement. For vehicular installations, monitor edge restraints for signs of loosening, cracking or shift; rectify promptly to avoid progressive failure.