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Canal Boat Insulation Suppliers
Canal Boat Insulation Suppliers
2 min read · Updated 2026-03-18
Canal Boat Insulation Suppliers
What this covers
Suppliers and installers of the thermal insulation that goes between the steel hull/cabin and the internal lining: spray polyurethane foam (the most common modern choice for narrowboats), rigid PIR/PUR boards, cork, sheep's wool, and acoustic underlay for floors. Some suppliers do supply-only; others offer mobile spray-foam application at the boatyard or marina.
What to look for
- Closed-cell spray foam at a density appropriate for marine use (typically 35–50kg/m³) — closed-cell resists moisture far better than open-cell and adds some structural stiffness.
- Application thickness matched to the build: 25–50mm on the cabin sides and roof is typical for liveaboards; less on hull below the waterline because of condensation routes.
- Continuity of insulation across ribs and beams to reduce cold bridging — these show up as damp lines on the inside lining in cold weather.
- For installers: spray-foam operators trained by their resin supplier, with appropriate PPE and ventilation arrangements during application.
- A clear position on what gets covered up — wiring, plumbing and any future-access points should be sleeved or routed before foam goes in.
- Material data sheets and fire-performance data; foams should be in line with the relevant BS EN ISO standards for combustibility in interior spaces.
- Red flags: open-cell foam offered as a cheaper alternative on hulls (it absorbs water), no masking of windows and electrical conduit, no reinstatement plan if foam needs to be cut for later access.
Common questions
Spray foam or rigid board? Spray foam fills awkward shapes and bonds to the steel, drastically reducing condensation. Rigid board is cheaper and DIY-friendly but harder to seal at edges and can leave cold gaps.
Will spray foam cause my hull to rust? Closed-cell foam properly applied to clean steel actually slows corrosion by excluding moisture and air. Problems come from foam over poorly prepared steel, or open-cell foam holding water against the hull.
Can I add insulation to an existing boat? Yes, but you'll need to remove internal lining. It's a major job rarely worth doing for marginal gains; usually undertaken during a full re-fit.
How thick is enough? 25mm closed-cell foam transforms an uninsulated boat. 40–50mm gets you close to diminishing returns for the cost and lost interior space.
Acoustic insulation under the engine? Yes — a few centimetres of automotive-grade acoustic foam in the engine bay makes a significant difference at cruising rpm.
When you need this
New build or sailaway fit-out, full re-fit, conversion of a workboat or hull, or remediation of a poorly insulated older boat suffering condensation problems.