Perimeter and Edge Insulation Detailing for UFH Screed

As with insulation boards and pipe fixing, perimeter strip is inspected as part of the pre-pour walk of the site, looking for gaps where other trades' work such as stud walls, door frames or service penetrations has disturbed it.

Where a doorway sits between two rooms on separate heating zones, or between a heated and an unheated area, the edge detail there is doing more work than a simple internal wall junction, and needs to be planned as part of the wider screed and manifold layout rather than treated as an afterthought.

Edge strip is available in a range of thicknesses, and the appropriate width for a given project depends on the anticipated slab movement for that floor area and heating design, rather than defaulting to whatever is readily available on site. Larger heated floor areas generally warrant a more generous allowance than a small room.

Where a heating designer has specified a particular expansion allowance for a large open-plan area, we work to that figure rather than a generic default width, since under-sizing the strip can leave the slab bearing directly on the wall at its warmest point, while an oversized strip simply wastes usable floor edge without adding benefit.

Where skirting boards are fixed to the wall before the screed pour, the edge strip needs to sit correctly behind or beneath them without being trapped in a way that stops the slab moving freely as it warms. We check this junction as part of the pre-pour walk, since skirtings fitted too early or too tightly against the floor are a common source of restricted movement.

Plastered or dry-lined walls finished down to floor level can also compress or displace edge strip if not protected during other trades' work, so we look for continuity along wall runs where recent finishing work has taken place, not just at the original insulation stage.

Once the floor covering is due to go down, the exposed edge strip is trimmed back to the finished floor height, and it's worth confirming at that stage that the strip has remained continuous around the room rather than assuming the original pre-pour check still holds after months of other trades working nearby.

A brief note or photograph of the perimeter detail before it disappears under skirting or covering gives a useful record if a query about expansion allowance comes up later in the project.