Conservation & Heritage Issue 50 Winter 2025/Spring 2026 - Flipbook - Page 68
A Breathable Floor
Ledger Stones and Archaeological Care
The approach taken at St Mary’s was rather than using
an impermeable concrete slab and plastic damp-proof
membrane, instead a breathable limecrete floor laid over
recycled foam glass aggregate insulation was specified. This
combination is designed to achieve thermal efficiency while
allowing moisture to move naturally through the structure.
As with most centuries’ old parish churches, they usually
feature stone floors incorporating memorial slabs and ledger
stones commemorating past parishioners. These stones
are often integral to the building’s character and must be
carefully recorded, lifted, and reinstated.
During the St Mary’s Stebbing project, timber shutter boxes
were used to guide the limecrete around the areas designated
for the ledger stones. This ensured that the new heating
system and pipework could be installed without disturbing
the integrity of the historic memorials.
Archaeology was another key consideration. Any ground
disturbance within a medieval church has the potential
to reveal burials or earlier floor levels. In this instance,
The Diocese of Chelmsford required a written scheme of
archaeological investigation and works proceeded under
professional archaeological supervision.
Above, excavation works
Project Manager and Head of the Church Restoration
Department at Bakers of Danbury, Adrian Ward explains
how this system
“
does not sit on a concrete base, but on a bed of expanded
glass insulation, which allows the building to breathe.
The limecrete screed which is a mix of natural hydraulic
lime and aggregate, then provides sufficient strength
for stone and brick flooring while maintaining vapour
permeability.”
Above, underfloor heating pipework being laid
This approach addresses a common problem in older
churches, where introducing impermeable materials can trap
moisture beneath the surface, driving damp up into walls
and causing long-term damage. A breathable system such as
this, keeps the moisture balance stable and the fabric of the
church protected.
Above, flooring with limecrete screed applied
‘Low and Slow’ Heat for Sensitive Buildings
Underfloor heating in churches operates most effectively
when designed for steady background warmth rather than
rapid temperature changes. This “low and slow” approach
reduces thermal stress on ancient materials, minimises
condensation, and provides a more comfortable and stable
environment for parishioners.
At Stebbing, over a mile of pipework was laid beneath
the nave and aisles. The system is powered by a new LPG
boiler, with provision for future conversion to bio-LPG as
Above, foam glass aggregate
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