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Diasen D20

5 litre (out of stock)

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  • Product Overview
  • Technical Details
  • Downloads
  • Installation guide

Product Overview

Main purpose

A primer for preparing surfaces for paint and other surface treatments such as Diasen Decork.

Use it on

Internal or external new plasters and dusty, absorbent surfaces.


D20 is a water-based acrylic primer mainly used over new plasters to ensure excellent long-term adhesion and a long-lasting finish for paints and surface finishes such as Diasen Decork and Diasen Cork Render. It can also be used on dust-producing absorbent substrates. D20 is transparent and can be applied by brush, roller or sprayed.

Where to use it

Diasen D20 can be used internally and externally on all types of new plaster and dust-producing absorbent substrates. It should always be used over Diasen finishing plasters prior to any application of Diasen Decork or Cork Render.  

D20 is not suitable for non-absorbent surfaces, Diasen Grip Primer should be used instead. 

What it does

D20 improves the adhesion of breathable paints like Diasen Decork to absorbent or dusty surfaces. It has high vapour permeability and retains the breathability of the wall. 

It is an essential component when using Diasen Decork or other breathable paints on top of Diathonite insulating plasters, Argatherm and Argacem Ultrafine. It effectively stabilises and prepares the surface prior to painting. 

D20 is suitable for new builds and retrofits, including heritage and listed buildings.

How it works

Diasen D20 is a ready-mixed and ready-to-use transparent water-based acrylic primer. It requires no dilution before use and can be applied (in one or two coats) by brush, roller or sprayed. It dries quickly in approximately 3 hours at 20° and 40% relative humidity. 

Why we love it

Diasen D20 is water-based, solvent free and non-toxic. It dries quickly so does not delay the application of the final finish paint or Decork.  

D20 was used in a project that tackled damp and improved thermal performance of a heritage cottage; read the article here.


  • Safe-to-use
  • Water-based and breathable
  • Non flammable


  • With high vapour permeability, maintains full breathability of the wall.
  • Easy to apply with brush, roller or spray.
  • Dries quickly so won’t hold up the application of the final paint finish
  • Solvent free, non-toxic and non-flammable so can used in projects with environmental requirements.
  • CE marked and compliance with Irish and UK standards  


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Technical Details

Key Technical Data

Technical Datasheet

  • Download

Material Safety Datasheet (MSDS)

  • Download

Declaration of Performance (DOP)

  • Download

Installation Guide

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How to Install

The surface must be stable, dry and clean. Do not wet the surface prior to application.

There is no need to dilute the primer before application. Apply D20 in one (or two) coats by brush, paint roller or spray. Make sure the surface is fully covered. At 20° C and 40% relative humidity, it will be dry in 3 hours. Drying time may be significantly longer in cooler temperatures or higher levels of relative humidity.

If the primed surface gets wet (e.g. with rain) before it is fully dried, confirm the surface is still fully covered with primer prior to painting. If there are any doubts, apply one more coat of D20. It is best to use more primer than risk poor adhesion of the final finish.

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