1 · Substrate prep

Existing internal plaster removed back to masonry. Loose pointing made good. Old gloss paint mechanically abraded. Salt-affected areas treated with a salt-neutralising base render at low level if the damp survey flagged historic rising-damp loading. The substrate condition matters — damp + salts + sealed IWI is the failure pattern we avoid.

2 · Salt & damp survey

Calcium silicate is more forgiving of damp substrates than rigid foams (you can't trap moisture behind a capillary-active board the way you can behind PIR), but salt loading still matters. Hygroscopic salt test kit run at sample points before fixing. Affected low-level masonry gets a render pre-treatment.

3 · Adhesive bed

Redstone-specified calcium-silicate-based adhesive applied to the back of each board. Full-coverage on uneven substrates — no air gap behind the board (an air gap defeats the capillary cycle). Boards pressed into the bed, plumbed, levelled, butted tight at joints. Adhesive sets within 24 hours.

4 · Mechanical fixings (optional)

Most installs adhesive-only; mechanical fixings added on weak or uneven substrates where the adhesive bed alone isn't trusted. Polymer plug-and-pin fixings drilled through the board face into the masonry, flush-set, hidden by the plaster skim. No thermal bridge, no corrosion path.

5 · Joint reinforcement

Self-adhesive scrim tape over every butt joint and at perimeters where new IWI meets original wall plane. The scrim and the board face together give the plasterer a continuous, paper-tested surface. No need for skim-coat reinforcing mesh on flat wall planes; mesh corner beads at returns.

6 · Plaster finish

Standard gypsum plaster skim (Thistle Multi-Finish) for general retrofit. Lime plaster (Mike Wye, Singleton Birch) for listed-building consents where vapour-open finish is specified. Both bond directly to the calcium silicate face. Finished thickness 2–3 mm. Decorate normally — breathable paint or paper.

Calcium silicate hydrate matrix

The board is a hydrated calcium silicate mineral — same chemistry as the bound phase in set cement, but in a high-porosity foam structure. Manufactured by autoclaving a lime + silica + water slurry under high pressure and heat. The result is roughly 90% porosity by volume, with pore sizes tuned for capillary activity.

230 kg/m³ density

Bulk density that delivers the moisture-buffering capacity. Higher than EPS (~30 kg/m³) or PIR (~35 kg/m³), comparable to wood fibre. The mass is what gives the board its moisture storage volume — a denser, more porous matrix can hold and release more water vapour per m².

100% inorganic mineral

No plastic content. No organic binder. No flame retardant chemistry. No formaldehyde resin. The board is calcium silicate hydrate, end of bill of materials. Cradle-friendly disposal — disposes with construction rubble, no hazardous-waste designation.

Alkaline pH ~10

The board surface sits at pH ~10 by chemistry, not by coating. Mould species need pH closer to neutral to colonise; calcium silicate's natural alkalinity is the inherent mould-resistance mechanism. The pH doesn't wash out or wear off — it's the chemistry of the board itself.

Fire: A1 non-combustible

Pure mineral matrix, no organic content, no contribution to fire. Euroclass A1 — the highest non-combustibility classification available. No 11 m external wall height restriction. Specifiable on leasehold mansion blocks and multi-occupancy buildings without EWS1 form friction or freeholder fire-engineering objection.

Manufactured in the Netherlands

Redstone manufactures the Clima Redboard Pro range at their facility in the Netherlands. European-made, short supply chain to UK projects (typically 1–2 weeks lead time from order). 100-year design life backed by manufacturer documentation.

100-year design life

Redstone publishes a 100-year design life for Clima Redboard Pro in standard internal wall service. The calcium silicate hydrate matrix is chemically stable mineral — it doesn't degrade, off-gas, embrittle, or lose performance over time. Set-and-forget fabric measure.

No annual service required

No moving part, no electrical component, no filter, and no consumable. Standard plastered-wall maintenance only — touch up dents and paint marks, redecorate on the homeowner's normal cycle. The capillary-active core needs nothing.

Decorate as a normal wall

Once plastered, the wall behaves like any plastered wall. Breathable paint (Earthborn, Graphenstone) preferred for full vapour-open assembly; standard emulsions work too. Wallpaper, hung pictures, fixed shelving — all supported. Heavy fixings (kitchen wall units) need fixings through the board into the masonry beyond.

Cold-bridge strip at reveals

A wall-plane IWI scope without insulated window reveals fails its U-value calculation around openings. Thinner Clima Redboard at 30 mm — or Spacetherm CBS where every millimetre of reveal matters — wraps jambs, soffits, sills, and lintels to break the thermal bridge. Without it, condensation reappears around windows on cold mornings.

Decentralised MVHR

Capillary-active calcium silicate buffers moisture peaks, but it isn't a substitute for ventilation. A decentralised MVHR unit per habitable room handles background moisture removal — iV-Compact or PRANA wall-mount where through-the-wall ducts are workable. The combination is what eliminates damp permanently, not the board alone.

Heating rebalance

An IWId room loses heat far more slowly than the existing radiator was sized for. The original radiator becomes oversized; the room overheats. A heating rebalance — typically lockshield valve adjustments across the existing system, occasionally a radiator downsize — restores even comfort. Included for one-room scopes; quoted separately for whole-floor work.