Merlin Barrier Coat (DPM)

Merlin Barrier Coat is a durable solvent-free surface DPM specially formulated for use as both a liquid damp proof membrane (DPM) or vapour control membrane for use in new build and refurbishment projects. Merlin Barrier Coat is a durable solvent-free epoxy coating system specially formulated for use as a water-resistant membrane in both new build and refurbishment projects. Barrier Coat can be applied directly onto wet surfaces free from standing water and when used as a primer and allowed to cure will accept most adhesives, coatings and screeds. Barrier Coat has been tested and certified to meet BS 476 surface spread of flame, Class 0 and has been assessed by the Building Research Establishment for water vapour permeability.


Related Downloads

icon-pdf TDS Merlin Barrier Coat with Calcium Sulphate Screeds

 icon-pdfTDS Merlin Barrier Coat_General Guidance_SMET

icon-pdf Merlin Barrier Coat Base _Safety Datasheet

icon-pdf Merlin Barrier Coat Activator – Safety Datasheet

icon-pdf SMET Floor Screed and Compounds Product Selector

Benefits of Merlin Barrier Coat

• Very high water vapour resistance
• Excellent adhesion to wet concrete
• Will tolerate lightly contaminated substrates
• Can be safely used on calcium sulphate screeds
• Suitable for use with underfloor heating
• Can be applied to metal, timber, concrete, ceramic tiles, fibreglass, brick, and most existing coatings
• Penetrates into wet substrates
• Fire retardant
• Available in temperate and tropical grades

Areas of Use

• Damp proofing concrete and cementitious screeds (DPM)
• Vapour release control for Calcium Sulphate Screeds
• Sealing and priming cementitious surfaces
• Sealing and priming lightly contaminated substrates
• Surface DPM
• Can also be used in combination with other Merlin Coatings Systems

Technical Details for Merlin Barrier Coat

Mixing Ratio 3:2 by weight
Application Rate
  • 1st coat 4 m_ per kilo
  • 2nd coat 6 m_ per kilo
Porosity of the substrate can affect coverage
Working life 40 minutes @ 20° C
Dry film thickness
  • 1st coat: 225 microns
  • 2nd coat: 150 microns
  • Total: 375 microns
  • Minimum Application Temperature: 8° C
  • Maximum air RH: 100%
  • Maximum slab RH: 99%
Cure time:
  • Touch dry: 12 hours @ 20° C
  • Foot traffic: 18 hours @ 20° C
  • Over coat: 14 hours @ 20° C
Lap shear adhesion:
Adhesion to damp concrete (abraded):
Adhesion to wet concrete (applied through surface water):
  • 16.0 Mpa
  • 10.0 Mpa
  • 4 Mpa
Hardness 84 Shore D
Flash Point Over 100° C


Case Studies using Merlin Barrier Coat

• Loughborough University*
• Dalham Hall Stud
• Sheffield Children’s Hospital*
• Ford UK
• Teeside Shopping Retail Park
• Thistle Oil Platform
• Kings High School for Girls
• Avery Mews Care Home*
• Eden Community School*
• Grandholm Care Home*
• Wakefield College*

*applied to calcium sulphate screeds

Packaging: Available in 5kg and 25kg units.

Damp Proof Membrane FAQs

What is Merlin Barrier Coat? – Merlin Barrier Coat is a proven high-performance liquid applied damp and vapour control membrane.

What does Merlin Barrier Coat do? – Merlin Barrier Coat adheres to difficult substrates including those with high moisture content or hydrocarbon (oil) contamination and then enables less tolerant materials to be installed onto or applied to it.

How does Merlin Barrier Coat work? – Merlin Barrier Coat works in two ways firstly during application it displaces any moisture within the substrate surface ensuring high levels of adhesion. Secondly, once cured Merlin Barrier Coat regulates the rate that water vapour is allowed to leave the substrate surface.

How does a vapour control membrane work? – Most materials will allow moisture vapour to pass through them, therefore establishing this rate for the membrane enables simple calculations to be performed that can then be used to predict the effect of other materials fixed to it. Another major factor is the ability of the membrane to adhere (stick) to a difficult substrate, this value must be greater than its cohesive (internal) strength of the system so vapour passes through it rather than lifting it away from the surface.

How do I know Merlin Barrier Coat will work? – Merlin Barrier Coat has been used successfully over several years on many major projects in Europe, Africa and the Middle East. Merlin Barrier Coat has also been extensively tested by world-renowned institutions and organisations.

Will Merlin Barrier Coat work on floors incorporating underfloor heating? – Merlin Barrier Coat is safe to use on floors incorporating underfloor heating subject to certain conditions. Refer to our preparation and application guide sheets for further information.

Can I use Merlin Barrier Coat with existing screeds?Merlin Barrier Coat can be used on existing floor screeds, please refer to our preparation and application guide sheets.

Is it safe to cover Merlin Barrier Coat?Merlin Barrier Coat can safely be covered by any material which has a vapour transmission rate greater than 3 grams of water vapour per square metre per 24 hours.

Will Merlin Barrier Coat work on calcium sulphate screeds?Yes Merlin Barrier Coat has a proven track record of use on calcium sulphate screeds both as a separation primer and vapour control membrane. In fact, Merlin Barrier Coat was the first material of its kind to be recommended by major screed manufacturers.

Can Merlin Barrier Coat safe be used in domestic premises? – Yes Merlin Barrier Coat has been used in domestic properties for many years.

Can Merlin Barrier Coat be used externally?Yes Merlin Barrier Coat can be applied externally onto correctly prepared surfaces subject to climatic conditions, refer to the relevant preparation and application guide.

What surfaces can Merlin Barrier Coat be applied to?Merlin Barrier Coat can be applied to most surfaces including steel, timber, concrete, ceramic & quarry tiles, fibreglass, composites, some plastics and soft metals. For further information please contact our technical department.

Will Merlin Barrier Coat work in hot climates? – Merlin Barrier Coat has been used successfully for many years in Africa and the Middle East. We even produce a tropical version, especially for hot climates.

Are there any things that cannot be applied or stuck to Merlin Barrier Coat? – Merlin Barrier Coat will accept most coatings, screeds, floor coverings, adhesives and primers subject to certain conditions. Please refer to the relevant preparation and application guide sheets for more information.

Do I need special skills to use Merlin Barrier Coat?Anyone capable of mixing two materials together and using a paintbrush or roller can apply Merlin Barrier Coat onto a correctly prepared substrate.

What if I can’t complete the job in one go can I join up to the treated area at a later date?Yes Merlin Barrier Coat can be applied in sections. To ensure no voids are left the Merlin Barrier Coat should be overlapped by a minimum of 100 mm (4 inches) along all edges. Should the existing Merlin Barrier Coat have reached full cure the surface may require preparing first, refer to the preparation and application guide.

What size units do Merlin Barrier Coat come in?Merlin Barrier Coat is available in both 5 and 25-kilogram units.

How much Merlin Barrier Coat will I need?We recommend Merlin Barrier Coat is applied at the rate of 4 square metres per kilo for the first coat and 6 for the second. To calculate the material required firstly establish total area in square metres then divide the total value by 4 for the first coat and 6 for the second. I.e. if the length is 12 metres and the width is 5.5 metres this would equate to a total area of 66 square metres so to complete the project would require;

1st coat 66 divided by 4 = 16.5kilos so 4 x 5kilogram units
2nd coat 66 divided by 6 = 11 kilos so 3 x 5kilogram units
Total material required 7 x 5-kilogram units

Why do I have to use the mixed Merlin Barrier Coat in one go?Merlin Barrier Coat cures by a chemical reaction similar to some adhesives; this reaction once started cannot be stopped without damaging the product in typical conditions this gives a working life of 40 minutes.

Can I split a unit into smaller parts?The simple answer is no, Merlin Barrier Coat is a chemically curing material and each component must be added in the correct ratio for it to harden correctly.

Does Merlin Barrier Coat need a lot of preparation?  To ensure you get the maximum performance from Merlin Barrier Coat it must be applied to a correctly prepared substrate, please refer to the relevant product preparation and application guide.

Do I need any special equipment to use Merlin Barrier Coat?  All that is required to use Merlin Barrier Coat is a suitable mixing paddle, a paintbrush to cut in around the edge and a short pile roller sleeve and frame.

Does Merlin Barrier Coat smell?  Merlin Barrier Coat activator has an ammonia type odour when the container is first opened but once mixed it has a light generic smell.

How long does it take for Merlin Barrier Coat to dry?Typically Merlin Barrier Coat is dry enough to overcoat within 14 hours and take foot traffic after 18 hours. Please note the cure times are dependent on climatic conditions, should you have difficulty providing ideal conditions please contact our technical department for further information.

Where can I buy Merlin Barrier Coat?Barrier Coat is available direct from Merlin Coatings Ltd and a limited number of specialist distributors.

How fast can I get Merlin Barrier Coat? Merlin Barrier Coat can be usually be delivered within 48 hours of order for mainland UK, should you require information on other areas please contact our sales team.

Do you ship worldwide?We can supply Merlin Barrier Coat worldwide subject to transport restrictions please contact us for further information.

Who are Merlin Coatings Ltd?Merlin Coatings Ltd are an independent coatings manufacturer specialising in providing solutions for problem applications primarily for the oil, gas and construction industries.

What makes Merlin Coatings Ltd different?Merlin Coatings concentrate solely on our area of expertise; we prefer to work with other experts in their fields to develop mutually beneficial solutions for the customer rather than competing against them with an inferior offering.