1 · Existing floor lifted

Original solid floor lifted — Victorian flagstones salvaged for re-use where the brief allows, original quarry tiles photographed and catalogued, existing concrete slab broken out. Sub-base soil exposed and assessed: moisture content, level, presence of voids or settlement. Depth to dig out is the first practical question on every heritage floor scope.

2 · Sub-base prepared

Sub-base levelled to the target depth — typically 300–400 mm below finished floor level depending on the depth of build-up specified. Compacted with a plate compactor. Geotextile fabric laid over the prepared sub-base to prevent fines migrating up into the Glapor void network over decades.

3 · Glapor poured

Aggregate delivered in bulk bags or tipper trucks depending on site access. Poured into the floor cavity to the target depth — typically 200–300 mm before compaction. Levelled with a rake to maintain consistent depth across the footprint. Sloped where the project specification requires drainage falls (rare in floors; more common in roof terrace sub-bases).

4 · Plate-compacted

Walked over with a plate compactor to lock the grains together mechanically. Compaction reduces the loose-fill depth by ~10% to the design compacted depth — the spec is given as compacted thickness, not as-poured. The compacted layer achieves 0.6 MPa compressive strength, structurally rated to carry limecrete or screed directly above.

5 · Limecrete poured direct

Limecrete poured directly onto the compacted Glapor — no membrane, no separation layer. Typical limecrete depth 75–100 mm, mixed on site with NHL5 hydraulic lime and a graded aggregate per the heritage spec. Cured over 5–7 days under controlled humidity before any finishes are laid.

6 · Finish floor laid

Heritage-appropriate finish on top of the cured limecrete — solid oak floorboards, salvaged Victorian flagstones, original quarry tiles relaid, or new natural finish. The finished floor sits at the same level as the original (or slightly higher) depending on the build-up depth versus the original floor level.

100% recycled post-consumer glass

Crushed bottle glass, container glass, and flat glass cullet — diverted from landfill or low-grade aggregate streams. Each m³ of Glapor incorporates ~150 kg of recycled glass content. EPD-published; specifiable into BREEAM and LEED.

Foamed at ~900°C

Crushed glass mixed with a small amount of carbon, melted in a tunnel furnace at ~900°C. The carbon oxidises in the molten glass, releasing CO₂ that creates the closed-cell foam structure. The cells are sealed inside each grain; the voids between grains form the drainage network when the aggregate is poured loose.

Two grain sizes for two scopes

Glapor 10/60 (10–60 mm) is the standard heritage floor size — fine enough to compact uniformly, coarse enough to drain freely. Glapor 20/40 is the deeper-fill size for larger sub-base scopes (frost protection, deep void fills, terrace base layers). Same chemistry, different grading.

Hydrophobic chemistry

Glass is naturally hydrophobic; the foamed structure preserves this. Water entering the layer drains through the void network between grains rather than absorbing into the grain itself. The bulk material's λ value is unchanged after immersion — important for floor applications below DPM level.

Fire: A1 non-combustible

Pure mineral glass, non-combustible Euroclass A1 — the highest non-combustibility class available. No organic content, no flame retardant chemistry. Suitable for any building height, any application context. Matches the limecrete chemistry above and below it in the floor build-up.

Made in Germany by Glapor

Glapor Werk Mitterteich GmbH — manufactured at the Mitterteich facility in Bavaria, Germany, since 1985. The foam glass aggregate pioneer in Europe; reference installations across the Austrian and German Passivhaus heritage retrofit programmes.

100+ year design life

Glass-based mineral aggregates have geological-timescale stability. Properly installed Glapor remains in service for the life of the building. No degradation under static load, no microbial attack possible, no chemistry change in service.

No annual service required

No moving part, no electrical component, no consumable. The aggregate sits compacted under the limecrete for the life of the building. Standard limecrete inspection cadence applies — visual review every 10–15 years for crack pattern on the finished floor; remediation of the limecrete layer (rare) doesn't disturb the Glapor below.

Doesn't lose performance when wet

Glapor is unique among loose-fill insulation materials in having zero water absorption — water passes through the grain void network rather than absorbing into the grains. Saturation events (flooded site, rising-damp episode, leak from above) don't degrade the λ value or compressive strength. The aggregate self-drains as the water source clears.

Geotextile separation layer

The geotextile fabric between the sub-base soil and the Glapor stops fines migrating up into the void network over decades. Skipping this layer to save £200 on the scope leads to gradual void infill over 30–50 years and a measurable degradation in drainage performance. CleverBloom installs geotextile on every Glapor floor scope as standard — included in pricing.

Limecrete cure time

Limecrete cures slowly — typical 5–7 day initial cure under controlled humidity, 28 days to design strength. Walking on the slab before initial cure compromises the limecrete; loading with heavy furniture or fittings before full cure risks cracking. We programme the cure window into every project schedule and communicate it clearly to the main contractor and the homeowner.

Foamglas Perinsul at the plinth

For a properly closed thermal envelope, the floor insulation needs to meet the wall insulation at the perimeter. Foamglas Perinsul HL (already in CleverBloom's range) handles the structural thermal break where the floor meets the wall plate — same chemistry family as Glapor, same brand, integrated detail at the slab-edge junction.