Repair Systems — Rising Damp
Breathable render systems
Technical product reference for breathable external render systems on masonry walls affected by rising damp — mineral, silicate and lime renders that allow moisture vapour to escape during the wall drying-out period after DPC injection treatment.
What are breathable render systems for rising damp remediation?
Breathable render systems are vapour-permeable external render products used on the external face of masonry walls undergoing or following rising damp treatment. The defining property is vapour permeability — the render must allow moisture vapour to escape from the masonry substrate as the wall dries out after DPC injection treatment, rather than trapping it beneath an impermeable film.
Mineral renders (cement-based), lime renders and silicate renders are all vapour-permeable. Acrylic renders and polymer-modified renders typically have significantly lower vapour permeability and are not appropriate for use on walls still drying after rising damp treatment. Applying an acrylic render to a rising damp wall traps moisture, accelerates salt crystallisation damage at the render surface, and causes premature render failure.
For external rising damp walls, the treatment sequence is: DPC injection → old external render stripped → wall begins to dry → breathable mineral or lime render applied to external face → WTA renovation plaster applied to internal face. The breathable external render system allows the wall to continue drying through both faces during the post-treatment drying period.
Do not confuse with:
- WTA renovation plasters (Remmers SP, Mape-Antique) — internal plasters for rising damp walls — different product category — see the salt-resistant plaster page
- Acrylic or polymer-modified renders — not breathable — not appropriate for rising damp walls — will trap moisture and fail
- Crystalline waterproofing slurries (Xypex, Vandex Super) — positive-side active waterproofing — not a breathable render for rising damp
- Breathable masonry paint (Keim Granital, silicate paint) — a topcoat coating — not a render system — see the breathable paint page
- Textured acrylic topcoat coatings — acrylic-based — not vapour permeable — not suitable over rising damp walls
Product Reference
3 products — 3 brands — mineral, silicate and lime breathable render systems for external masonry walls after rising damp treatment
System Description
Parex Monorex GT is a through-coloured mineral scraped-texture render widely used for external masonry facades in Australia. As a mineral render, Monorex GT is vapour-permeable (breathable) — it allows moisture to escape from the masonry substrate while providing a durable, through-coloured decorative finish. This breathability is a key property for use on masonry walls affected by rising damp or undergoing the drying-out period after DPC injection treatment. Monorex GT is applied as a one-coat render system typically at 15–20mm thickness to sand-and-cement-prepared or direct-to-masonry backgrounds. The scraped texture finish is applied while the render is green, using a nail float or scraper to create a uniform aggregate-exposed surface. The through-colour eliminates the need for topcoat paint immediately and provides a natural mineral appearance that has become standard in contemporary Australian apartment and medium-density residential construction. For rising damp remediation on external walls, Monorex GT can be used as the external finish coat over a suitable breathable undercoat scratch coat where the existing render has been stripped. Confirm with Parex Australia that Monorex GT is the appropriate product for the specific rising damp remediation application, the required background preparation, and whether an undercoat is required for the specific substrate.
Technical Properties
- Mineral through-coloured render — no topcoat required immediately — colour integral throughout the render body
- Vapour-permeable (breathable) — allows masonry substrate to dry through the render layer during rising damp drying-out period
- Scraped-texture finish — applied while green — consistent aggregate-exposed surface — standard Australian apartment aesthetic
Limitations
- Confirm suitability for rising damp applications with Parex technical — verify substrate preparation and undercoat requirements before specifying
- Not a WTA renovation plaster — not suitable as a replacement for internal WTA salt-resistant renovation plaster on internal rising damp walls
- Background must be sound, clean and free of contamination — rising damp walls require old contaminated render to be stripped before application
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
Keim's mineral silicate render system is part of the same silicate chemistry family as Keim's flagship Granital silicate paint. Silicate renders use potassium silicate as the binder, which undergoes a petrification reaction — a chemical bond — with silica-containing masonry substrates including brick, sandstone, concrete and traditional renders. This chemical bond creates a render that cannot peel, crack or delaminate in the way that acrylic or polymer-modified renders can. The key property for rising damp applications is exceptional vapour permeability. Silicate renders have among the highest breathability of any render system — far higher than acrylic or polymer-modified renders. This allows masonry walls to continue drying freely during the post-treatment period without moisture being trapped beneath the render layer. For heritage buildings with soft masonry substrates (sandstone, handmade brick, traditional lime mortar) where breathability is critical to prevent moisture-driven damage, silicate render is the technically correct choice. Keim is a German manufacturer with a long heritage in silicate coatings and renders. Keim products are available in Australia through Keim Australia. Confirm the complete render system, application requirements and substrate suitability with Keim Australia before specifying.
Technical Properties
- Potassium silicate binder — petrification reaction with silica-containing masonry — chemical bond — cannot peel or delaminate
- Exceptionally high vapour permeability — among the most breathable render systems available — allows masonry to dry freely after rising damp treatment
- Very high alkalinity — inherently resistant to algae, fungi and biological growth without biocide additives
Limitations
- Only bonds chemically to silica-containing substrates — not suitable for substrates without silica content — confirm substrate compatibility with Keim Australia
- Application is more demanding than acrylic or polymer-modified renders — qualified Keim applicators are required for best results
- Colour range is limited to mineral earth tones — synthetic bright colours are not achievable in silicate systems — confirm colour options with Keim Australia
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Remmers Kalkputz / NHL Lime-Based Breathable Render
Lime-based breathable render
System Description
Remmers supplies lime-based breathable render products (under their Kalkputz or equivalent product designations) as part of a WTA-referenced rising damp treatment system for external masonry walls. Lime renders are the traditional breathable render for masonry construction and have inherently high vapour permeability, good salt tolerance during the wall drying period, and compatibility with soft historic masonry substrates where harder Portland cement renders can cause damage through differential stiffness. In the Remmers WTA rising damp system, a lime-based breathable render on the external face is the logical companion to Remmers SP WTA renovation plaster on the internal face — both products are part of an integrated Remmers WTA system that is designed to provide coordinated system documentation, technical support, and warranty coverage across the complete treatment. Using a single manufacturer for the injection product (Kiesol C), internal renovation plaster (SP) and external render provides administrative simplicity on larger strata remediation projects. Confirm the current Remmers product designation for lime-based breathable external render with Remmers Australia before specifying — the Remmers product range is broad and the exact product name and system recommendation may vary between projects.
Technical Properties
- Lime-based binder — naturally high vapour permeability — allows wall to dry freely through the render after rising damp treatment
- Good salt tolerance during drying — lime renders do not have the enlarged pore structure of WTA renovation plasters but tolerate salt exposure better than Portland cement renders
- Heritage masonry compatible — compatible with soft brick, sandstone, traditional lime mortar backgrounds — does not cause moisture trapping behind impermeable surfaces
Limitations
- Lime renders have lower mechanical strength than Portland cement or polymer-modified renders — confirm suitability for the exposure and traffic conditions
- Lime renders require correct application conditions — protection from frost, strong sun and drying winds during the curing period
- Application by experienced plasterers is important — lime renders behave differently from Portland cement renders and require appropriate trade knowledge
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Brand Equivalents
Breathable render equivalents by render type. * Confirm WTA system compatibility and substrate suitability with manufacturer before specifying.
| System type | Parex | Keim | Remmers |
|---|---|---|---|
| Mineral through-coloured scraped render — external | Monorex GT | — | — |
| Silicate render — max breathability — heritage | — | Mineral Silicate Render* | — |
| Lime-based breathable render — WTA system | — | — | Kalkputz / NHL render* |
Do not apply acrylic or polymer-modified render over rising damp walls — vapour trapping causes premature failure
- Acrylic renders and polymer-modified renders have low vapour permeability — they trap moisture within the masonry wall behind the render and accelerate salt crystallisation damage at the render-masonry interface
- Rising damp walls drying after DPC injection need to breathe through both faces — applying an impermeable render on the external face traps moisture and prevents the wall from drying
- Acrylic render failure on a rising damp wall manifests as blistering, spalling and render delamination — typically occurring within 12–24 months of application
- Only mineral renders, lime renders or silicate renders should be applied to external masonry walls still in the drying-out phase after rising damp treatment
Disclaimer
Information is general only. Product selection must be confirmed against project requirements, substrate type and condition, manufacturer technical data sheets, and applicable standards. Confirm vapour permeability of selected render is appropriate for the application stage. Do not rely on this reference as a substitute for professional advice.