Installation • RAL
RAL installation: sealing in three levels
The joint between window and wall must be airtight inside, insulated in the middle and rain-proof outside — while still letting moisture in the joint escape. That is what the RAL installation guidelines require, and that is how we install.
- Tighter inside than outside
- No thermal bridges
- No draughts or mould
- Good practice and EN 14351-1
The three-level principle
Three levels, three jobs
The basic rule: tighter inside than outside. Moisture from the room must not get into the joint, and any moisture that does must be able to escape outwards.
1 · Inner level
An airtight, vapour-tight tape stops warm, humid room air from entering the joint and condensing there.
2 · Middle level
Thermal and acoustic insulation (PU foam or mineral wool) fills the joint and prevents thermal bridges.
3 · Outer level
A watertight but vapour-permeable tape keeps out rain and wind while letting moisture from the joint escape.
- Inner airtight tape
- Joint insulation
- Outer vapour-permeable tape
Schematic drawing, not to scale.
Why not just foam
Why foam-only installation fails over time
| PU foam only | Three-level installation | |
|---|---|---|
| Room moisture | Enters the foam and condenses | Stopped by the inner tape |
| Rain and UV light | Break down unprotected foam outside | Outer tape protects the insulation |
| Insulation over time | Wet foam loses its insulating value | Insulation stays dry and effective |
| Result | Draughts, cold reveals, mould | Warm edges, no draughts or mould |
How we work
Installation step by step
Measuring and preparation
We measure the opening precisely and plan the joint for the wall type and facade insulation.
Fixing
The window is fixed with screws or anchors and packers so loads are transferred to the wall correctly.
Three-level sealing
We fit the inner tape, fill the joint with insulation and close it with the outer vapour-permeable tape.
Check and handover
We adjust the hardware, check operation and sealing, and leave the room clean.
Warranty and standards
Installation you can rely on
We install according to the RAL guidelines for window and door installation and good trade practice; our products comply with EN 14351-1. Warranty terms for products and installation are stated in your quote and warranty certificate.
- Installed by our own team
- Removal and disposal of old windows
- Finishing of reveals on request
Why us
More advantages of our windows and doors
Enquiry & quote
Request a made-to-measure quote
Tell us what you are planning. We come to measure on site, advise you on profiles, glazing and colours, and prepare a quote for your building.
- On-site measuring
- Advice on systems, glazing and colours
- A quote prepared for your building