What coating should I use to paint my concrete floor?
Firstly, is the concrete new or old?
If the concrete is still 'green' (very new) then before anything else is done you need to consider whether you require a liquid dpm (damp proof membrane) prior to applying the coating. The time period required to be able to apply a coating will depend on the type of coating to be used. For example a water based coating can generally be applied earlier than a solvent free or a solvented coating, and some single pack coatings require the concrete to be at least two years old prior to applying them. Check the data sheet for the individual product to be used. For instance FS Epoxy Sealer (2 pack water based epoxy coating) can be used once the moisture content is less than 10% and the concrete is a minimum of 14 days old, FS Epoxy Coating (solvent free, 100% solids epoxy coating) can't be used until the moisture content is down to 5% and the concrete is also a minimum of 28 days old, although it will often need to be older than this to get down to this moisture content. Rust-Oleum 7100 mustn't be used until the concrete is at least 2 years old!
What is the floor going to be used for?
For light foot traffic a single pack floor paint could be sufficient. For heavier foot traffic a single pack product will do the job but it may be more cost effective in the long term to use a two pack epoxy or two pack polyurethane. For the majority of industrial usage a two pack product is generally better and if wheeled traffic is to be used a two pack product is definitely recommended. Also a high build, solvent free coating like FS Epoxy Coating is likely to give a longer service life than a water based or a solvent based product. It's worth noting that if a vehicle is parked for some time on a floor coated with a single pack paint it is likely that when it is moved the paint will lift.
Generally a two pack product is much more durable than a single pack one and, despite it being more expensive, it will normally work out cheaper in the long run. For most uses an epoxy coating is more practical than a polyurethane as it is easier to re-coat. Polyurethanes are also generally solvented and often quite smelly.
Whatever coating is used it is most important to prepare the substrate to ensure that it adheres properly.
For many projects an existing finish will need to be removed prior to coating the floor. Generally these finishes should be removed prior to re-coating.
If the new coating to be applied is of the same type as the existing one, and it is adhered properly, then it may not be necessary to remove the old one. If, however the existing coating is de-bonding at all it should be removed. When painting over an existing coating it is still necessary to clean this thoroughly and to give the surface a mild grind, probably with an STR machine.
Preparation is completed by mechanical means, using some form of grinding or shot blasting, with a heavy duty vacuum attached, to ensure a clean and laitance free surface. For larger projects it is worth considering using a specialist floor preparation company to undertake the preparation.
Should a primer be used?
Generally a primer, such as FS Epoxy Primer will enhance the life of the floor finish, although it is often not specifically required. Always check the data sheet for the specific product to be used.
As mentioned above, for very new concrete a dpm primer, such as FS Epoxy DPM Primer, should be used. If in doubt check the moisture content of the concrete. Note that two coats are generally required. A dpm primer should also be used for older concrete where there isn't an existing damp proof membrane in the concrete itself.
If the surface of the concrete is friable then a good primer will help to bind the surface and greatly improve the life of the coating.
The information in this article is intended as an overview and you should always check with the product data sheets for the specific product to be used. Alternatively give us a call for advice.
Terry Hudson – Director