Timeline
How long does external wall insulation take?
About two weeks on site for an average semi-D, weather aside. Here's each step in order, what slows it down and the SEAI grant window.
Free, no obligation. One SEAI-registered contractor prices it, not five.
- €6,000SEAI grant, semi-D
- €6,000SEAI grant for a semi-D
- 150 mmmost homes can add without planning
About two weeks on site for an average semi-D. NSAI's homeowner leaflet says the work should be complete within a fortnight, not counting weather and other delays. The grant adds time before that: SEAI must approve it before work starts, and you have 8 months from the offer to finish, get the BER and claim.
How long does external wall insulation take on site?
NSAI puts an average semi-detached house at within a fortnight, weather and other delays aside. A detached house has more wall, a mid-terrace has less, so expect a semi-D's time to move up or down with the wall area. energyefficiency.ie says the whole job can take several weeks in total, because the layers take time to dry.
What happens, in order
- Survey and U-value calculation. SEAI says walls must be assessed before work starts, to check for any existing insulation, and a U-value calculation done to reach 0.27 W/m²K.
- Grant approval. The SEAI grant offer must be in place before any work starts. Start first and the grant is lost.
- Services moved. NSAI says external insulation must not go over electricity wires and cables. An ESB Networks service alteration may be needed, and downpipes and gullies may need moving. Book the ESB early.
- Scaffold and preparation. The walls are checked for cracks, damp, mould and structural damage before anything goes on.
- Boards, basecoat and mesh. The base coat should only go on when the weather is expected to stay dry for 48 hours (energyefficiency.ie).
- Finish coat, sills and reveals. Reveals, heads and cills are insulated and new over-cills fitted where needed (NSAI).
- Post-works BER and the claim. A registered BER assessor does the post-works BER, then you return the paperwork to SEAI, all within 8 months of the grant offer.
What slows it down
- Rain and cold. Render needs dry weather to cure. A wet spell can stop the job for days.
- The ESB cable. If the supply cable runs across the wall, the service alteration has to happen before the boards go on.
- Wall repairs. Loose render, cracks or damp are fixed first.
- Roof line. NSAI says roof lines may need altering for the thicker wall, without blocking roof ventilation.
Can you stay in the house?
Yes, in most cases. The work is outside, so you live in the house with scaffold up. NSAI says your installer should check the home's ventilation before starting and tell you about any shortfall, so ask about vents in the walls being kept open.
Grant timeline at a glance
| Stage | Time |
|---|---|
| On-site work, average semi-D | Within a fortnight, excluding weather |
| Grant offer to claim | 8 months, including the post-works BER |
| Base coat weather window | Dry for 48 hours |
FAQ
Questions people ask
How long does external wall insulation take?
About two weeks on site for an average semi-D. NSAI says it should be complete within a fortnight, not counting weather and other delays.
How long do I have to finish after the SEAI grant offer?
8 months from the grant offer to finish the work, get the post-works BER and return the paperwork to SEAI.
Can external insulation be done in winter?
It can, but the base coat should only go on when the weather is expected to stay dry for 48 hours, so wet spells add days.
Do I have to move out?
No. The work is outside. You live with scaffold up for the weeks it's there.
Your grant
Your house wrap grant in 3 taps
Tap your home type, when it was built and any earlier wall grant. Your SEAI grant shows as you go. Then leave your number and one SEAI-registered external insulation contractor who covers your area rings you with a price.