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Diasen Argacem Ultrafine

25kg Bag

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This calculation is based on a thickness of 2mm being applied in two 1mm layers.
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  • Product Overview
  • Technical Details
  • Downloads
  • Installation guide

Product Overview

Main purpose

To create perfectly smooth surfaces and maintain the breathability of the wall/ceiling.

Use it on

Argatherm, Watstop, old and new lime or cement-based plasters and prefabricated concrete panels (internal use only).


Diasen Argacem Ultrafine is a white smoothing plaster skim coat for Diathonite plasters. It is lime-based, highly breathable and mould resistant.  It is made from hydrated lime, micro crystalline sand, marble powder and natural additives. It is highly workable and must be applied by trowel. It can also be finished with a plastic float.

Where to use it

Argacem Ultrafine is suitable for interior walls and ceilings only. It can be applied on top of fully dry Argatherm with no further preparation required. 

It may also be used over new or existing lime and cement-based plasters that have a robust surface free of dust, debris and materials that might affect the adhesion like paint, silicone, grease and salt deposits. It is suitable for new builds and retrofits, including Heritage and Listed buildings.

Do not apply Argacem Ultrafine over gypsum plaster, metal, plastic surfaces or any surfaces painted with a waterproofing agent.

Before you start your project, it is essential to investigate and fix any existing damp or moisture related issues in the wall; please see our installation guide for full details.

What it does

Diasen Argacem Ultrafine is a lime-based skim coat plaster that can smooth out the roughness of grainy plasters without affecting the breathability of the wall. It creates a finely textured almost smooth surface on to which a natural breathable paint can be applied.

It is naturally mould resistant due to the alkalinity of its ingredients.

Argacem Ultrafine breathable plaster skim is porous and absorbent so must be protected with a breathable natural paint like Auro.  

It is easy to mix and has excellent workability for trowel application and finishing with a float. It is available in 25kg bags.

How it works

Diasen Argacem Ultrafine is lime-based and in combination with Diathonite plasters, regulates the moisture of the wall.

Why we love it

Argacem Ultrafine breathable plaster skim contains only natural materials and qualifies for LEED points, which means it can be used in projects with strict environmental requirements. Any experienced lime plasterer can install it without special training.

It is easy to mix with just clean water to create a consistent mixture with excellent workability. As it is non-combustible and does not emit smoke, Argacem Ultrafine also improves the fire safety of the building.


  • Smoothest of finishes
  • Compression resistant
  • Lime based
  • Fireproof/non-combustible
  • Just add water


  • Creates a breathable more modern smooth aesthetic finish due to its small grain size.
  • Completes a robust and durable wall system.
  • Helps regulate humidity and prevent mould growth in combination with Diathonite plasters and as a final finish to Argatherm.
  • Does not burn or smoke so improves fire safety of the building.
  • Easy to mix with excellent workability for trowel application.


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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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Before You Start

Before installing any internal wall insulation, it is essential to investigate and fix any existing damp or moisture related issues in the wall. Even though our internal wall systems are breathable and provide optimal protection against condensation, persistent damp issues must be resolved first. A wet wall is a cold wall, so preparation to remove or reduce external sources of moisture is key to achieving optimum results. 

Once damp issues have been resolved, the wall should be allowed to dry thoroughly and re-assessed for suitability of internal wall insulation.

These are the main considerations before commencing any work:

  • Is there evidence of moisture in the walls?
  • Is there any evidence of condensation, fungus or mould growth on the internal walls?
  • Is there a functioning damp proof course (DPC)?
  • Is there sufficient ventilation in the property?
  • Is the external ground level higher than the floor level inside?
  • Are there any structural defects in the external walls?
  • Is guttering, flashings and external pipework in good condition?
  • Is the external render, pointing or cladding in good condition and providing adequate weather protection?
  • Is the external finish suitable for the severity of wind driven rain exposure?
  • Are the timber joists embedded in external walls free from infestation and rot?
  • Has the building ever been flooded?
  • If you chose not to remove existing plaster on the wall, is this plaster fully compatible with the insulation system being used? (Ideally, it would need to be lime-based)

How to Install

Add 10-11 litres of clean water per bag of Argacem Ultrafine and mix with an electric drill mixer until it creates a smooth mixture without lumps. The amount of water required is an indicative amount and will depend on the room temperature and humidity. No other substances should be added in the mixture. Let the mixture rest for 5 minutes then mix it again before applying with a trowel.

Argacem Ultrafine should be applied on top of Argatherm semi-smooth finishing plaster with a stainless-steel rounded edge trowel. For optimal results, Diasen Polites-80 reinforcing mesh must also be embedded within the Argatherm when it was applied (details here). The mesh is essential when using Ultrafine over Argatherm to prevent any potential cracking over time.

The total thickness of Argacem Ultrafine should be 2mm. It is important not to exceed 1mm per layer to ensure the finish will be very smooth with no bubbles or dimples. 

The first 1mm layer of Argacem Ultrafine should be applied 24 hours after applying Argatherm. The second 1mm layer can then be applied 24 hours after that. Try not to deviate from 24 hours between each layer and the application of Argatherm. 

After applying each layer of Argacem Ultrafine and while it is still workable, go over the surface again with the stainless-steel rounded edge trowel to obtain a high quality smooth finish.

At 23°C and 50% relative humidity, Argacem Ultrafine dries in 5-7 days. Under different room conditions, drying time may vary significantly. 

In very hot weather, if the Argacem Ultrafine is drying to quickly, you can mist it with water to prevent it drying out.

Always use protective gloves and a dust mask.

Please note Argatherm finishing plaster is the replacement for Argacem HP (which is now discontinued).

Argacem Ultrafine smooth finish to internal walls
Argacem Ultrafine smooth finish to internal walls
Argacem Ultrafine smooth finish on a hallway
Argacem Ultrafine smooth finish on a hallway
Argacem Ultrafine smooth finish on an arched doorway
Argacem Ultrafine smooth finish on an arched doorway
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