Painting Conservatories and Orangeries: A Technical Guide
How to paint a conservatory or orangery properly — aluminium frame preparation with etching primer, uPVC coatings, masonry bases, and dealing with moisture and temperature cycling.
A Challenging Environment That Rewards the Right Approach
Conservatories and orangeries are among the most technically demanding painting projects a decorator encounters. The combination of large glass areas, mixed substrate materials — aluminium, uPVC, timber, masonry, render, brick — and an environment subject to extreme temperature and moisture cycling means that material selection and surface preparation are not optional refinements. They are the difference between a finish that lasts three years and one that lasts fifteen.
This guide covers every substrate you are likely to encounter in a London conservatory or orangery project and what to do with each.
Aluminium Frames: The Etching Primer Rule
Aluminium is a non-ferrous metal with a natural oxide layer that forms within hours of any fresh surface being exposed. This oxide layer is chemically inert and provides poor adhesion for conventional primers and topcoats. Attempting to paint bare or freshly abraded aluminium without an appropriate primer is the single most common cause of failure in conservatory refinishing work.
The correct approach:
Surface preparation: Degrease thoroughly with a panel wipe or isopropyl alcohol. Abrade with 180–240 grit wet and dry to create a mechanical key. Remove all sanding residue.
Primer: Apply a two-pack etch primer or a single-pack self-etching primer such as Rust-Oleum Self Etching Primer or Hammerite Metal Paint Primer (etch formulation). These contain phosphoric acid compounds that chemically react with the aluminium oxide layer to create a positive bond. Without this step, subsequent coats have no durable mechanical or chemical adhesion.
Topcoat: Once the etch primer is fully cured (minimum 24 hours at 15°C+), apply a quality metal paint in your chosen sheen level. For external aluminium frames, two-pack polyurethane or alkyd enamel finishes offer the best durability. Bedec MSP (Multi Surface Paint) in Satin or Semi-Gloss is a water-based option that performs well on aluminium in conservatory environments.
Powder-coated aluminium that is sound but faded can be repainted without stripping back to bare metal — degrease, lightly abrade, prime with a bonding primer such as Zinsser Bulls Eye 1-2-3, and topcoat as above.
uPVC Frames: Adhesion Is Everything
uPVC is the other common frame material in conservatory construction, particularly in projects completed from the 1990s onward. It is glossy, non-porous, and has essentially no tooth for conventional paint adhesion. Standard paints simply peel off within months if applied without preparation.
The Plasti-kote approach: Plasti-kote's Plastic Paint range is specifically formulated to bond to uPVC without adhesion promoter, and works well on conservatory trims and smaller uPVC sections. Apply in thin coats (the material is designed to self-level) in two to three passes. Available in a limited range of colours.
Primer-based system: For larger uPVC areas where colour choice matters, use a specialist adhesion promoter — Polytrol or Prep Coat — followed by a quality topcoat. Bedec MSP is widely used by professional decorators on uPVC for this reason; it is flexible, hard-wearing, and maintains adhesion through the thermal expansion cycles that uPVC undergoes.
Do not attempt to paint uPVC conservatory frames in a standard emulsion or gloss without adhesion preparation. It will fail.
Masonry and Render Bases
Many orangeries and better-quality conservatories in London incorporate a low masonry wall — typically brick, render, or stone — at the base of the glazing. This section behaves identically to any exterior masonry wall and should be treated accordingly.
Check for dampness before applying any paint. Use a moisture meter; anything above 20% moisture content is too high for painting. In older properties, the damp proof course may be compromised at the conservatory junction — this needs to be addressed structurally before any surface treatment.
For sound, dry masonry: apply Zinsser Peel Stop or a masonry stabiliser if the surface is friable or chalky, then use a quality exterior masonry paint such as Dulux Weathershield, Johnstone's Stormshield, or Farrow & Ball Exterior Masonry for a premium finish. Apply by brush into any surface texture; a roller alone will not fill the pores adequately.
Rendered masonry that is cracked or has localised areas of blown render must be hacked back and repointed or rendered before painting. Painting over cracks in exterior render is not a solution — water will enter, freeze, expand, and force the repair to fail faster than if it had been left unpainted.
Temperature and Moisture Cycling: Why It Matters
A conservatory is one of the most thermally dynamic spaces in any building. In London's climate, the temperature differential between a winter night (close to 0°C) and a July afternoon with the sun on the glass (potentially 40°C+ internal surface temperature) is enormous. Every material in the structure expands and contracts with these cycles, and paint films must accommodate that movement without cracking or delaminating.
This is why:
- Rigid, brittle oil-based gloss applied to uPVC is likely to crack and peel within one to two years.
- Flexible water-based systems with higher elongation (such as Bedec MSP, or two-pack water-based polyurethane) cope better with thermal cycling.
- Primer and topcoat systems must be compatible — a rigid topcoat over a flexible primer creates an interface that will delaminate as the two layers move differently.
Internal conservatory walls and ceilings present their own challenge. In an unheated conservatory, condensation forms on walls regularly in winter months. Anti-condensation paints such as Thermilate InsOlate or Ronseal Anti-Condensation Paint incorporate insulating microspheres that raise the surface temperature of the wall slightly and reduce the frequency and severity of condensation. They are not a substitute for improving ventilation and thermal performance, but they extend the life of the painted surface considerably in a conservatory environment.
A Word on Internal Decoration
If the conservatory or orangery is fully heated and insulated — as modern orangeries increasingly are — the internal decoration can follow broadly normal interior principles. The key differences are: ensure all paints are moisture-resistant rather than standard emulsion, pay close attention to the ceiling area above the ridge (which is subject to trapped humidity), and use eggshell or satin finishes rather than flat matt on all surfaces for easier cleaning.
Get the Right Advice Before You Start
A conservatory or orangery project involves more substrate complexity than almost any other painting job. Getting product selection wrong costs money and time. Contact us for a free quote and we will assess your specific conservatory or orangery, identify every substrate present, and give you a detailed specification that will last.