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A waterproofing primer’s purpose is to ensure the substrate is fully sealed and prepared to receive a coating. It also also allows for excellent adhesion between the membrane and the substrate by providing a good key. Additionally a primer can provide a good barrier between the existing substrate and the waterproofing membrane. Waterproofing primers are mainly used on porous materials, and they tend to make the surface more solid and able to accept a waterproofing membrane.
Primers can come as one or two-part systems. Primers are an adhesion promoting product which can also act as a blocker. An example of this would be stopping bitumen bleed from a felt roof. There are a number of different primers available for specific substrates.
The Importance Of Peel Tests Before Applying A Waterproofing Membrane
Although there are many universal primers which are suitable for most surfaces, there are cases where a primer is not necessary. This means a peel test should always be carried out to identify if a primer is necessary. Typically, old felt and asphalt are the most common products that fall into this bracket. However, it is always good working practice to apply a primer as it will not only stop bitumen bleed in the long run, but enable optimum coverage of liquid. Therefore saving time and money.
A peel test is incredibly important and is part of what is commonly summarised as ‘good working practice’. Not carrying out a peel test could have dire financial consequences, both short and long term. For instance, some membranes simply do not adhere as certain substrates require a primer for adherence. So, what might initially appear to be a cost saving shortcut could result in the waterproofing membrane peeling away after just a few weeks or months. Potentially resulting in astronomical costs.
This would be due to the cost of removing the waterproofing membrane. Applying primer to the substrate then re-applying a waterproofing membrane. In effect this would more than double the cost of the project, with materials and labour needing to be paid twice (plus the cost of removing the defective membrane and priming).
If a waterproofing primer was used from the start of the project would have been delivered on time and within budget. Another consequence of not using a waterproofing primer when it should have been is site disruption. The removal of a defective waterproofing membrane would lead to other trades being affected. This would lead to further repercussions in terms of time and budget.
A primer also makes the surface stronger and smoother due to the epoxy content. There are a number of different primer types such as:
Single Component Porosity Primers
These are typically used to seal completely dry concrete and cementitious surfaces. They can also be used on asbestos and brickwork.
Epoxy Type Primers
These can be used to seal moist concrete. It is always best however to allow the concrete to not be coated for at least 28 days as sealing moisture is considered by many not to be good working practice. However, the way modern construction is carried out means rapid solutions are required and modern primers which can deal with moist concrete surfaces are available.
These are normally one component, low viscosity liquids which cure due to the humidity in the atmosphere. They are especially effective when used for porous concrete and wood.
This can depend on the substrate type and the condition it is in. But generally, always ensure the surface is clean and free of loose particles. The surface temperature should be between 5°C and 35°C. Primer is very easy to apply. On virtually every substrate a brush or roller is used. Typically, an application rate of between 100 and 200gr/SQM is enough on most surfaces.
The absorption can vary however, as a rough battered old felt substrate would absorb more primer than a new felt system. The primer can be applied in one or two coats. Regarding felt and asphalt, the primer will ensure that you get more liquid spread as the primer has in effect encapsulated the substrate and the liquid coating can therefore be more easily controlled, allowing optimum spread rate, with the added subsequent benefit of keeping the liquid coating costs down.
Another benefit of primer is if the installation of a liquid roofing system gets interrupted and a delay of longer than a few days occurs, due to prolonged bad weather or other circumstances. A thin final coat of primer can be reapplied, and the coating works can carry on. This is commonly called tack coating.
The main substrates where Mariseal Aqua Primer, which is a two-component epoxy primer which can generally be termed a universal primer. It is used would for polyurethane waterproofing coatings, polyurethane joint sealants and polyurethane and epoxy floor coatings, asphalt and felt. It is also used on non-absorbent surfaces like concrete, metal, tiles, glass, and acrylic coatings. It has many benefits including:
• Low Odour.
• Very high anchoring abilities to absorbent and non-absorbent surfaces.
• Due to the mixture of water when it is prepared it is okay for use on moist surfaces.
• Provides high tensile and impact strength.
• Works well in high or low temperatures.
Ideally a surface should be dry when a primer is applied. However, due to the mixing method and construction of Aquaprimer, it can be applied onto a slightly damp surface. This is due to the addition of between 15% and 20% of water to the product. The obvious bonus of this is if there has been a brief period of rainfall and moisture is present on the substrate surface, the primer can be applied as normal.
The reason for this is moisture is actually part of the curing process of this primer. This saves much time drying off the roof and enables preparation work to commence as normal. When the two parts A and B are mixed a reaction is caused, this is called cross linking. The liquid will be of a milky appearance turning clear when cured and ready for coating. Cold weather can slow down the curing of primer and hot weather can accelerate it. The main surfaces which require priming are; timber, concrete, PVC (sometimes an activator is best), ceramic tiles, glass, asphalt, bitumen, felt, screed and acrylic coatings.
Remember, a peel test should always take place on any surface as it confirms whether a product is suitable for the project before extensive works are carried out.
There are however some other surfaces where specialist primers should be used. The main ones being TPO and EPDM. TPO is considered to be a rubber roofing material. It is a blend of polypropylene and ethylene-propylene rubber. EPDM stands for Ethylene Propylene Diene Monomer. It is a synthetic rubber derived from oil and natural gas (ethylene propylene).
In hotter climates TPO reflects the sunlight more effectively. Whereas EPDM is a black rubber type compound and better absorbs heat. TPO is a relatively new product and is popular in countries with hotter climates. EPDM has been around much longer and has a superior life expectancy. However, due to the make up of both products, a special type of primer should be used with them.
The Mariseal TPO primer is a transparent, one part, solvent-based product. It works as an activator for these products which allows for maximum anchorage. Any surface, regardless of primer type, needs to be clean. It must be free from grease and oil to prevent problems with adhesion. Maximum moisture content should never exceed 5%. Any loose surface areas need to be thoroughly removed. When activating the surface for best results, the temperature during application should be, as in other optimum coating conditions, between 5°C and 35°C. The relative humidity should be between 50% and 70%. Low temperatures and low humidity as previously mentioned, extend curing time.
Application of Mariseal TPO primer is very simple. By soaking it into a clean, dry cloth then wiping the entire surface off. Change cloths often as they obviously get full of the dirt and grime which is being removed. Using the product in this way you ensure that besides the chemical surface activation, the surface is getting degreased. Wait approximately 2 hours before applying the liquid waterproof coating. In summary, the TPO primer is applied very simply with a cloth at a rate of 50 to 60 gr/SQM. It provides superb adhesion for liquid waterproofing products like Mariseal 250, TPO and EPDM. It is UV stable and quick drying. It can also be used on galvanised steel to ensure it is fully cleaned and grease free.
Primers are normally applied in two ways, brush or short haired roller. In the case of an activating primer, cloth is used for the application. Most primers are hazardous and should be treated with respect. When priming internal areas you should always ensure the area is well ventilated and that masks are worn.
Should I Prime Concrete?
Concrete and any cementitious surface should be primed.
How Long Do Waterproofing Primers Take To Cure?
This depends on the weather. In warm conditions some primers dry very quickly. For instance, Mariseal Aquaprimer can dry in as little as 30 minutes on a warm day. Typically, with same day primers you should allow at least four hours, but many epoxy based primers, especially in colder weather need at least 24 hours to be sure.
What Is A Peel Test?
A peel test is a scaled down replication of the larger works that will be taking place. So typically ,1m2 areas would be chosen and treated exactly the same as the whole area would be. These 1m2 areas should be in various places on the roof. The areas are cleaned primed/not primed, then coated with the liquid water proofing. 48 hours normally gives a fair indication as to what method works best and this is then carried out over the remainder of the project.
How Do I Know What Primer Is Best For A Particular Substrate?
Always check with the system manufacturer of the product you are using to waterproof the building as to the recommended primer.
Does The Substrate Have To Be Dry?
In most cases yes. There are some specialist primers that can be used on damp substrates. But always consult the manufacturer.
What Is A Typical Coverage Rate?
This depends on the primer. Typically, 100/200gm/m2 for an epoxy primer. Much less for an activator type used on PVC or TPO for instance. 50/60gm/m2
How Long Can Primers Be Effective Before Coating Starts?
Some answers vary on this, but certainly if the roof is left for more than two weeks another coat of primer should be applied just to be sure. However, also some primers are so robust that if a generous coat is applied they can almost be considered a temporary waterproofing for very short periods. But cannot be relied upon fully.
If you would like any further information about primers please contact us or call us now on 01277 375 511. Our friendly team of waterproofing specialists pride themselves on providing great service and will be delighted to help.None None