How external wall insulation is installed, step by step
The short answer
A typical EWI installation runs: survey and design, scaffolding, removing fittings, fixing a starter track, bonding and anchoring boards, meshing and basecoating, priming and finishing, then refitting services, removing scaffolding and getting building control sign-off. A semi-detached house usually takes three to four weeks on site.
The steps
- Survey and design: measurements, wall condition, details, planning and building control.
- Scaffolding: erected with room to work around the walls.
- Preparation: downpipes, lights and cables taken down; loose render removed; repairs made.
- Starter track: fixed above the damp-proof course, level and straight.
- Boards: bonded with adhesive, joints staggered, then anchored through to the masonry.
- Details: reveals insulated, sills extended, beads at corners and edges.
- Basecoat and mesh: mesh embedded with overlaps, diagonal patches at window corners.
- Primer and finish: applied in suitable weather and protected while curing.
- Reinstatement: services refitted on stand-off brackets, sealant joints, clean-up.
- Sign-off: building control completion and your photo record.
Weather
Render isn't applied in rain, frost or strong direct sun. Most products need temperatures above about 5°C while curing, so winter jobs can take longer.
Related services
Questions people ask
Can I stay at home?
Yes. All the work is outside.
How long is scaffolding up?
For the length of the job: usually three to four weeks for a semi, plus a day or two either side to put it up and take it down.