1 · Compacted sub-base

Standard new-build sub-base preparation per the structural engineer's design — Type 1 hardcore, compacted in layers, levelled to the design floor formation level. Geotextile fabric optional but recommended where the sub-base soil is variable. The sub-base level is what the structural engineer specifies; CleverBloom works to it.

2 · Foamglas Floor slabs

Slabs laid butt-jointed on the prepared sub-base. Joints offset between rows in a staggered pattern. Bitumen-adhered at edges where the engineer's spec requires (rare in floor applications; more common in podium deck and inverted roof contexts where slip resistance under the structural pour matters).

3 · Joint detail

Foamglas Floor butt joints are taped with manufacturer-specified vapour-control tape where the project specification demands a verified continuous vapour barrier. For standard residential under-slab work, the bulk material's vapour-tightness is sufficient and joint taping is optional. For Passivhaus and EnerPHit certification work, joint taping is the standard spec.

4 · Slab-edge detail

At the perimeter, the Foamglas Floor returns up the slab edge (typical detail: 100 mm vertical return) to meet the Perinsul HL plinth course or the wall's EWI insulation above. The detail closes the thermal envelope at the wall-to-floor junction — no cold bridge where the slab edge meets the masonry above.

5 · Reinforcement mesh

Standard structural mesh (A142, A193, or per SE spec) laid over the Foamglas slabs as the structural pour reinforcement. Mesh supported on standard chairs; chair bases sit on the rigid Foamglas surface without distorting the insulation. No protection board needed between the chairs and the slab.

6 · Structural concrete slab

Reinforced concrete slab poured directly onto the Foamglas Floor with the mesh in place. Standard slab thickness 100–150 mm per SE specification, with UFH pipework or services embedded where the project includes them. The Foamglas carries the wet-concrete load during pour and the cured slab load through the building's service life.

Cellular glass slab

Pure mineral glass foam manufactured at the Owens Corning Foamglas facility in Tessenderlo, Belgium. Same chemistry as Perinsul HL, formed into rigid slab geometry (600 × 450 × variable thickness) rather than the masonry-format block. Hot-cut to thickness from the manufactured billet.

60% recycled glass feedstock

A substantial proportion of the feedstock is post-consumer recycled glass — bottle and window glass diverted from landfill streams. EPD-published; specifiable into BREEAM and LEED. Each m³ of Foamglas Floor T3+ incorporates ~100 kg of recycled glass content.

Sealed-cell waterproof structure

Closed-cell glass foam — every cell is a sealed glass capsule. Zero water absorption through the bulk material. Zero water vapour transmission (μ effectively infinite). The bulk material is the damp-proof membrane and the vapour barrier in one — no separate DPM layer needed in the floor field above.

600 kPa T3+ compressive

Compressive strength at 10% deformation, the defining property of the T3+ slab grade. Residential and light-commercial slab loads sit comfortably within this rating. For heavier commercial slab loads (deep beam foundations, large podium decks, vehicle-bearing surfaces), T4+ at 900 kPa or T7 at structural-engineering specification.

A1 core fire classification

Pure mineral glass, non-combustible Euroclass A1 — the highest non-combustibility class available. Matches the concrete slab chemistry above and below. No fire-class discontinuity at the under-slab thermal break. Specifiable on any building height under Approved Document B.

Made in Belgium by Owens Corning

Manufactured at the Tessenderlo facility in Limburg, Belgium — Owens Corning's primary Foamglas production line. The chemistry has 80+ years of European architectural and industrial service history; originally developed for petrochemical pipe insulation in the 1940s, the architectural slab form is the modern application.

100-year design life

Owens Corning publishes a 100-year design life for Foamglas in standard service. Cellular glass is chemically inert mineral; no degradation in the under-slab environment, no chemistry change through the building's service life. The slab performs for the life of the building.

No annual service required

No moving part, no electrical component, no consumable. Once the structural concrete is poured above, the Foamglas Floor is entombed for the life of the building. Standard slab inspection cadence applies — visual review of the finished floor every 10–15 years, same as any concrete slab.

Doesn't lose performance when wet

Cellular glass is unique among insulation materials in having zero water absorption. Construction-stage flooding, prolonged rain exposure during the slab pour, or service-life moisture incursion from a failed DPM elsewhere in the building doesn't degrade Foamglas Floor's λ value. The material can't absorb water, so its thermal performance is unchanged after exposure.

Structural engineer approval

Foamglas Floor is a structural element — it carries the wet-concrete pour load and the cured slab load. Specification must reference the SE's approved slab load calculation; CleverBloom doesn't substitute Foamglas grades or change the layout on the bricklayer's discretion. Every project's SE signs off on the spec before fixing.

Perinsul HL at the plinth

For the complete below-ground thermal envelope, Foamglas Floor needs Perinsul HL above it at the plinth course. Without the plinth thermal break, the cold-bridge moves up to the wall-floor junction and the floor insulation's benefit gets eroded at the perimeter. CleverBloom typically quotes both as a coordinated below-ground scope on every new-build and deep retrofit project.

Joint taping for Passivhaus

For Passivhaus and EnerPHit certification work, manufacturer-specified joint tape across every butt joint is the spec — provides verified continuous vapour barrier performance documented in the PHPP and the certification audit. Standard new-build work doesn't always require this level; the bulk material is vapour-tight without taping for non-certified projects.