The Quick Answer
Yes and No! Resin Bound has very strong adhesive powers and can be installed over a number of bases. The structural integrity of the base is the main concern when considering installing Resin Bound directly over the existing surface. If the base is solid and has very little wear then this may be a better option than actually replacing it. If the base it broken, loose or unstable in anyway, a full dig out and preparation work is advised.
If you are counting on the resin install being permeable then the existing base would have to be SUDs Compliant. You can find out more on this here.
Resin Bound Overlays
A Resin Bound overlay is the process of using the existing base as a sub base and simply installing the Resin Bound directly over it (providing suitable edging and drainage is in place). Having a base that is suitable for an overlay can reduce the price by almost half that of what a full installation would cost (removing existing base, installing edging, sub base etc).Some contractors may offer the option of an overlay but reduce or even remove their guarantee from the install as they have not installed the base themselves. Some contractors will overlay almost any surface, however from experience 9/10 on these jobs tend to fail within the first couple of years, as Resin Bound is finishing product, therefore the structural aspects of the paving need to come from what’s underneath.
3 questions to ask yourself when deciding if a resin bound overlay is achievable for your driveway.
- Are there any trees nearby? Often this won’t be a problem, however, if there are large roots beneath the existing surface it could lead to movement or cracking in the sub-base which, will in turn damage the resin bound surface.
- Do you require a porous surface? If you are choosing resin bound for its permeability you should always check the permeability of the existing base. Chances are, this wont be porous. You will be required to add in suitable drainage.
- Is The Base Damaged? If the base is damaged it has likely been there a long time and is unstable. If you see any cracking or crumbling then always choose a full dig out over an overlay.
suitable Existing Bases
Providing the surface isn’t crumbling and not covered in cracks, concrete can be a solid base for resin bound. The main issue with overlaying concrete is that unless it’s a new pervious concrete base, it will not be permeable, which means suitable drainage needs to be installed.
Tarmac is the preferred base for Resin Bound surfacing. It offers durability, strength and structural integrity. If you have an existing tarmac driveway in good condition there is a good chance it will be able to be overlaid. Tarmac requires less preparation that concrete however the surface still needs to be thoroughly cleaned and fully dry before resin can be laid.
Unsuitable Bases For A Resin Bound Overlay
MOT type 1
A lot of resin bound specialists will say it is suitable to use MOT as a base when the intended function of the area is for foot traffic only. This being said, laying resin bound directly onto an MOT base is not good practice. No matter how well the MOT is compacted there will still be gaps which allow movement. This movement can result in surface cracking.
Block Paving is a very popular choice of driveway for many people. It has actually been around since mid 19th century, so it’s no surprise that 1000s of properties in the UK have it. Although it is extremely popular and trusted, it is very prone to weed growth. This can damage the structural integrity of the block paving, which in turn will effect the resin bound. There’s also the risk of shadow cracks along the block joints, which is caused over time.
Much like block paving, Paving Slabs are an extremely popular choice of decorative surfacing. Whilst they are aesthetically pleasing they are not renowned for their strength values. Paving slabs are usually used on patios and pathways rather than driveways for this reason. If you do have an existing base of paving slabs then do not allow resin to be laid over this. There is not enough strength there to ensure no movement will occur.
Part Overlays are also an option to reduce costs. Most contractors will be happy to split a driveway into sections depending on whether parts of it can be overlaid.