How to renovate metal roofs?

How to bring new life to steel sheet roofs that have problems with waterproofing, rusting or delamination of the original protective coating?

RD-Elastometal is a single component, high performance, water-based elastomeric coating that combines superior corrosion and waterproofing properties. A single-product system that is quick and easy to apply.

The products you need

How to restore your metal roof in videos


Surface preparation


The problem

Metal or sheet metal roofs are used to cover warehouses, factories, houses and many other types of buildings. They are subject to extreme conditions due to their permanent exposure to external weather conditions.

Sheets continuously expand and contract under the influence of heat and coldand must resist to rain, hail, snow, UV, pollution, erosion, etc.

Under the effect of these external conditions, rust and infiltration appear, sometimes quickly. The original coating peels off, which can cause a lot of damage: damaged stocks and production tools, ruined furniture, etc.

The solution


RD-Elastometal is a preventive and repair solution that will significantly extend the life of your roof by protecting it from corrosion and making it waterproof! It is a unique product that provides a great improvement in performance and longevity. It combines high waterproofing and anti-corrosion properties. It is even regularly applied to metal bridges in marine environments!

Applied to a steel sheet roof, the result is an elastic, rubber-like protective membrane that solves problems of water infiltration. The estimated service life is over 15 years! This water-based elastomeric coating is available in various colours and is UV-resistant, so it can be used as a primer and topcoat. Its permanent elasticity of over 200%, even at low temperatures, allows it to follow the expansion movements of the metal under heat influence.

Recommended quantity and thickness

Roof with a minimum slope of 4%:

RD-Elastometal: 0.8 kg/m² for 350 µ dry - 65 ft²/gallon for 14 mils dry, to be applied in a minimum of two layers. It is recommended to use two different shades when applying to distinguish the first coat from the second. This is a simple way to ensure that the correct amount is applied.

RD-Elastometal has excellent anti-corrosive, UV and weather resistant properties. Being single component and water-based, it is not a fire hazard or risk. It is suitable for application to occupied buildings and does not inconvenience the occupants.

Benefits of the system

This system offers multiple advantages for the contractor and the applicator:

- one-component and ready-to-use
- dryfall - low VOC (Volatile Organic Compounds) levels
- quick and easy to use solution
- fast drying time and reduced downtime
- extensively tested worldwide
- wide range of colours and very good durability

Our water-based products prevent:

- bringing hazardous products to the site while eliminating the risk of fire or explosion
- nuisances in the vicinity with annoying odours during and after application
- emissions of harmful substances
- losses during and after application

Getting ready


When working outdoors, avoid starting a job if rain is forecast within 4 hours of application.

A minimum of 12°C / 54°F is recommended for comfortable working conditions with higher productivity. Avoid working in direct sunlight, especially in very hot areas, where early morning or late evening work is preferred. Ensure that there is no condensation on the surface before and during application, and during the first hours of drying. In the case of facades, it is sometimes possible to work according to the rotation of the sun, preferring the shaded area in summer and in very hot weather and the sunny area in cooler weather. Ensure that there is no condensation on the surface before and during application, as well as during the first few hours of drying.

Good to know

RD-Elastometal has no overlap window. This means that if work is interrupted (e.g. due to a sudden weather change), it can be resumed later without any problems, after rinsing the surface with a high-pressure cleaner at a more or less moderate pressure, depending on the degree of soiling.


Avoid carrying out waterproofing work in autumn, winter or early spring when the weather conditions are sometimes too uncertain.

Surface preparation

The surface must always be clean, dry, degreased and free from any contaminant. The most convenient and quickest way to do this is to clean the surface using a high pressure washer powered at minimum 180 bar / 2600 psi equipped with a rotating zero degree angle nozzle. This method will remove non-adhering rust and contaminants, as well as existing paint showing lack of adhesion.


If the existing paint resists to the cleaning, it means it has sufficient adhesion and can stay in place.

Cleaning by hand with a metal brush or power tool is also an option and is advised when more detailed surface preparation needs to be done on objects near or on claddings, such as access ladders, ventilation, doors, bolts, etc. that would be rusted.

Moss and mold can be removed with suitable cleaners. Consider using biodegradable solutions that are easy to find and very effective.

Marine or polluted environments

Observe whether chimneys are blowing smoke in the immediate vicinity, which could cause accumulation of contaminants on the roof. In the sea area, salts accumulate rapidly on the surface. Spray the biodegradable RD-Eco Power Clean solution diluted in water over the entire surface and leave for +/- 15 minutes. Rinse with clean water.

Inspect and treat bolts

It is important to inspect the condition of the bolts securing the metal panels to each other and to the wall structure. Defective fasteners and bolts must be repaired or replaced. Brush a spot coat of RD-Elastometal over each fastener after inspection. This will not only help visualize the progress of the inspection, but also add a protective first layer to those weak spots.


Edges and ridges

Also check the edges and ridges of roofs and sheets. These are places easily subject to corrosion. Remove all contaminants and apply RD-Elastometal by brush. You will notice that it covers the edges perfectly and will protect them even more.

Non-ferrous metals and smooth surfaces

Degrease with RD-Eco PowerClean all non-ferrous metal parts such as aluminium, galvanised and stainless steel. RD-Monoguard may be required as a primer on new galvanised steel or stainless steel. RD-Elastometal can be applied directly to aged galvanised steel (> 1 year) and is diluted 25% with water when applied to aluminium.


It is preferable to apply RD-Elastometal with a brush on specific areas and with an airless sprayer on the main surface. If spraying is not possible, such as in the case of high winds, it is also possible to apply the paint with a roller. It will be necessary to apply more coats to achieve the minimum thickness required, but this remains a very reliable and easy option.

Specifications for an airless application:

RD-Elastometal: minimum output of 180 bars or 2600 psi. Nozzle between 0,017 and 0,023 inches.

Brush type: thick brush for water-based products.

Roller type: polyamid 14 mm / ½ inch for water-based products.

The application

Measuring existing thicknesses

In order to be able to control the thicknesses applied after application, it is advisable to measure the thickness of the existing coating on different areas in order to be able to determine the total newly applied thickness later on. The same holds true for galvanised steel roofs.

Use of RD-Roof Fleece ?

In the case of roofs with waterproofing problems, it is necessary to use RD-Roof Fleece on the overlaps between panels. This fleece should be applied along all overlaps or locally, if the origin of the leaks can be precisely determined.

Applying the RD-Roof Fleece

Use the fleece – RD-Roof Fleece – of 20 cm / 8 inches large and cut it to the needed length.

Lay the fleece evenly over the overlap of the panels and brush a layer of RD-Elastometal through it. This operation should be repeated on all overlaps or problematic ones.


Allow RD-Elastmetal to dry for at least 6 hours before covering. Depending on the weather, this may take more or less time.

Other areas may also require the use of the fleece:

  • very rusted areas
  • near chimneys and air outlets that give off fumes which may be aggressive or polluting
  • areas where water could stagnate
  • connections with walls or other elements on or along the roof


Preparing RD-Elastometal

RD-Elastometal is ready to use, stir it mechanically for a few minutes.

In very hot weather, add a maximum of 3% water to slow down the drying process, but never more than that so as not to reduce the anti-corrosive properties (except on aluminium, see above).


RD-Elastometal is best applied with an airless sprayer. It allows the recommended thickness of the first coat to be applied quickly in a single pass. Apply RD-Elastometal to the entire surface, following the slope of the roof.

The airless application of RD-Elastometal produces almost no mist. However, if it is hot and windy, it is recommended to work in such a way that the potential mist does not return to the fresh paint. The result is a smoother, more aesthetic finish.

Allow the paint to dry for +/- 6 hours before applying the second coat.

If applied by roller, a third or further coat may be required to achieve the recommended thicknesses. 



If the application has been interrupted for a few days, ensure that the surface is not contaminated by dirt or other pollution before resuming. If it is, rinse the surface with a high pressure cleaner.

Choose different colours for each coat. This ensures that you do not forget to apply in certain areas. RD-Elastometal has a very good covering power.

Details such as metal objects, corners and edges are usually applied with a roller or brush for greater precision. 

Measure the wet film thickness before it dries to determine the dry film thickness. 

The final thickness is important and must be in accordance with the recommendations. It is the guarantee for the future performance of RD-Elastometal.

The metal roof is now protected against water infiltration and corrosion.


Areas subject to persistent contamination

Surfaces in the vicinity of chimneys or air vents are sometimes subjected to contaminated airflows which, depending on their nature, can attack the coating and accelerate its deterioration.

It is recommended that one or two coats of RD-Hydrograff HP Clear be applied directly to RD-Elastometal in these areas once it has dried thoroughly. RD-Hydrograff HP Clear is a two-component water-based polyurethane varnish that is highly resistant to abrasion and chemical contamination.

A reflective finish to reduce heat transfer in the building?

Significant energy savings can be achieved by reducing the consumption of cooling equipment through the application of RD-Sunguard as a finish on RD-Elastometal. Also, in buildings without air conditioning, simply choosing an RD-Sunguard finish can reduce the building temperature by a few degrees on very sunny days.

RD-Sunguard is a single component water-based coating that is applied as a finish at a rate of 0.09 L/m². Its UV resistance, whiteness and excellent dirt pick up resistance make it an ideal finish in areas subject to hot and sunny climates.


VERS.   S7-230831