The surface you’re standing on is usually the last one anyone insulates.
Insulation between the joists, and the gaps sealed while we are down there.
Floors are the forgotten element of most retrofits. Walls and attics get done, the house improves, and a cold draught still crosses the room at ankle height every winter.
Where there’s a ventilated void under a timber floor, insulation is installed between the joists and supported from below, with the underfloor ventilation kept clear. Access decides the method: where there’s a cellar or a generous crawl space, the work is done from underneath with no disturbance upstairs. Where there isn’t, floorboards are lifted, insulation installed, and the boards relaid.
Alongside the insulation we seal the gaps — around skirtings, between boards, at service penetrations — because a suspended floor with cold air moving under it is as much an airtightness problem as an insulation one.
Insulated above the slab, with the level change designed in.
Solid floors are insulated above the slab, with rigid insulation and a new floor build-up over it, or as part of a full floor replacement where the slab is being dug out anyway.
Insulating above the slab raises floor level, which has knock-on effects for door heights, stair bottoms and thresholds. Those need designing in rather than discovering mid-job. Where floor height is genuinely fixed, high-performance thin insulation boards can get useful performance out of a very shallow build-up.
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If underfloor heating is in the plan, floor insulation stops being optional. Without insulation under the pipes or mats, a large share of the heat you generate goes into the ground.
This matters most with a heat pump. Underfloor heating over a well-insulated floor is the ideal low-temperature emitter, which is exactly the condition a heat pump needs to run efficiently. Over an uninsulated slab, the same system is expensive to run. If you are considering a heat pump, the floor build-up is part of that decision.
Floor insulation is most cost-effective when the floor is coming up anyway — during an extension, a deep retrofit, a kitchen replacement, or a re-level of a failing floor. Done in isolation it’s a more disruptive job for a smaller return than walls or attic. Our surveyors will tell you honestly where it sits in your priority list; for many homes it’s third or fourth, not first.
Less than through the roof or walls, but enough to matter — and the comfort difference is disproportionate, because cold floors and low-level draughts are what people feel most.
For a suspended floor done from below, no. For works from above, the rooms involved need to be cleared and out of use while the job runs.
On a solid floor insulated from above, yes. We’ll set out the build-up and its effect on doors and thresholds before starting.
Not without breaking it out. If the slab is staying, insulation goes above it.
Call 051 850722. We’ll tell you honestly where floors sit in your priority list — and when it makes sense to do them.
