Hemp-Lime Wall

Hemp shiv and lime binder cast in situ around a structural frame, tamped in lifts between temporary shuttering. Vapour-open and hygroscopic; the frame carries the load, not the infill.

Carbon and evidence

How This Is Made

An Environmental Product Declaration is issued by a manufacturer against a declared unit. This record has neither, so it states sourced facts about process and provenance instead of a carbon figure.

No published figure held

Introduced to UK practice in the 1990s; used in new build and in solid-wall retrofit

Process

Feedstock

Plant fibre

Hemp shiv, the woody core left after fibre extraction; UK-grown crops exist alongside imports

Process heat

Calcined

The lime binder is calcined at roughly 900 C. The wall reabsorbs CO2 through carbonation as it cures and over its life. Both are real; neither is netted against the other here, and no figure is claimed for either.

Binder

Lime

Fabrication

Site-formed

Sourcing: national to European, depending on the shiv

Who Builds It

Trained contractor

Limited UK availability

Slow to dry — several weeks before finishes, longer in a wet autumn. The drying programme, not the mixing, is what governs the build

End Of Life

Separable

The infill is broken out and the frame released; the crushed material has been used as a soil conditioner rather than landfilled

Maintenance: Breathable render or limewash only; no sealants, no cement render

Specification Risk

What a specifier has to resolve before this can be built.

Certification: No BBA/Agrement for the cast-in-situ buildup; specified by precedent and by supplier test data
Fire: Reaction-to-fire depends on the binder ratio and the finish; confirm the tested buildup rather than assuming
Warranty: Contractor workmanship warranty; the binder supplier warrants the binder only
Insurance: Warranty providers vary — confirm acceptance before the design is fixed
Supply: A small contractor base; secure the trade early

Read This Honestly

•Not structural. The frame carries the load; hemp-lime is insulating infill.
•Distinct from a hemp-lime block (IsoHemp, Hemp Block Company), which is a manufactured product with a published declaration and belongs in the product track.
•No published carbon range is held for this buildup. Carbonation is often quoted as a net benefit; that calculation is not made here.