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Cloister School, a finished two-storey school of 1911 in rubble stone with brick dressings and a three-arched cloister at its left, seen across its frosted east court in low winter sun.

Keep the building. Meter the difference.

Keepstone repairs old masonry and timber buildings to a signed energy target. We take our last 15% only when a year of meter readings meets it.

Book a surveyRead the ledgers

Sample figure

57%

Heat demand removed across five finished buildings

0target 52%

next reading 30 Sep 2026 Sep 2025 – Aug 2026 · 9,220 m² · heat meters: 57.2% against 52.1% · checked by Sallow & Pike · [1]

How to read a ledger

Solid is done. An outline is a promise.

We draw every target as an outline before work starts and fill it only with what the meters record. Every bar in our ledgers reads the same way, including the ones that fall short.

Sample figure

5 of 12

Months of meter data at Wellgate Pump House

Solid · 5 months meteredOutline · 7 still to come

due Apr 2027 Counted Aug 2026 · heat meter live since Apr 2026 · [1]

  • Outline

    A target or a pledge. It stays empty until a meter fills it.

    due Apr 2027 Wellgate Pump House, heat demand removed · target 50%

  • Fill

    The measured share, drawn at true length and never rounded up.

    Cloister School, air leakage removed · 72% of an 80% target · [2]

  • Past the line

    A result that beats its target runs past the end of the outline.

    Cloister School, heat demand removed · 61% against 55% · [1]

  • due Jun 2027

    Due date and record line

    Promises carry a due date in an outlined tag. Fills and photographs carry a record line saying when, where, how and who checked.

    Blower door at 50 Pa · Cloister School, Mar 2025 · checked by Sallow & Pike · [2]

Sites

Six handed over.
Four still in outline.

6of 10

Frames 1–2 of 10

Buildings finished and metered, of the ten under contract

Counted 25 Sep 2026 · handover certificates · [8]

  1. Lathe Barn, a timber-framed barn used as a joinery workshop, its doors open onto a gravel forecourt.

    52%

    Lathe Barn, c. 1780

    Heat demand removed · target 45%

    Handed over Jun 2022 · 360 m² · photographed Jan 2026 · [1]

  2. Ferrier’s Mill, a two-storey brick mill with tall timber windows, photographed square on.

    57%

    Ferrier’s Mill, 1884

    Heat demand removed · target 50%

    Handed over Nov 2023 · 1,480 m² · photographed Jan 2026 · [1]

  3. Cooper’s Row, three brick terraced houses with painted doors, photographed square on.

    47%

    Cooper’s Row, 1896

    Heat demand removed · target 50%, missed

    Handed over Mar 2024 · 480 m² · photographed Jan 2026 · [1]

  4. Cloister School, the stone school of 1911 with brick dressings, across its frosted east court in winter sun.

    61%

    Cloister School, 1911

    Heat demand removed · target 55%

    Handed over Feb 2025 · 4,200 m² · photographed Jan 2026 · [1]

  5. Colonnade Wing, a limestone school wing with a four-pier entrance porch, photographed square on.

    54%

    Colonnade Wing, 1926

    Heat demand removed · target 50%

    Handed over Aug 2025 · 2,700 m² · photographed Jan 2026 · [1]

  6. Wellgate Pump House, a brick engine hall with three tall arched windows, photographed square on.

    5 of 12

    Wellgate Pump House, 1908

    Months metered · heat reading due Apr 2027

    Handed over Apr 2026 · 1,120 m² · photographed at handover · [1]

  7. The old dairy, 1928

    Signed target · heat demand down 55%

    1,850 m² · contract signed Aug 2026 · works start Nov 2026

  8. Brick Row, 1899, 24 flats

    Signed target · heat demand down 50%

    2,300 m² · survey done Apr 2026 · contract signed Jul 2026

  9. The parish hall, 1932

    Signed target · heat demand down 45%

    640 m² · survey logged Jun 2026 · contract signed Jul 2026

  10. The maltings, 1890

    Target set after the six-week survey

    1,900 m² · survey booked Nov 2026 · letter of intent signed Sep 2026

Ledgers

Read every target we signed.

Each building’s ledger sets the target we signed beside the meter reading and the name of the checker, misses included. It updates every month, and the owner sees the page we see.

  1. Cloister School

    Our largest job and our best year. Heat and comfort beat their targets. Air leakage fell short, because sealing the east range’s floor voids meant lifting boards we had promised to keep.

    Type
    Two-storey school with a cloister
    Place
    Hollinbrook, east court
    Year built
    1911
    Materials
    Rubble stone with brick dressings, slate, timber sashes
    Use
    Primary school, 240 pupils
    Ownership
    Hollinbrook Schools Trust
    Sources
    Heat meters [1], blower door [2], loggers [6]

  2. Colonnade Wing

    A limestone wing that is still drying out. Heat beat its target in the first year, but six test points in the stone still read damp, so the holdback waits for the checker.

    Type
    School wing with an entrance colonnade
    Place
    Fenwick Road, Hollinbrook
    Year built
    1926
    Materials
    Limestone, slate, steel windows
    Use
    Sixth-form teaching, 14 rooms
    Ownership
    Hollinbrook Schools Trust
    Sources
    Heat meters [1], pin meter [4], waste tickets [5]

  3. Cooper’s Row

    Three terraced houses where we missed. Heat fell 47% against the 50% we signed, the party walls still leak to next door, and the owners kept the holdback. The ledger says so.

    Type
    Three terraced houses
    Place
    Cooper’s Row, Millbank
    Year built
    1896
    Materials
    Brick, slate, timber sashes
    Use
    Three family homes
    Ownership
    Three private owners
    Sources
    Heat meters [1], blower door [2], payments [7]

  4. Wellgate Pump House

    Five months of data, so four of its rows are still outlines. They fill once the meters have seen a winter. Our own studio is on its first floor.

    Type
    Former waterworks engine hall
    Place
    Wellgate, river frontage
    Year built
    1908
    Materials
    Brick, slate, cast-iron windows
    Use
    Offices, with our studio upstairs
    Ownership
    Wellgate Building Trust
    Sources
    Heat meters [1], waste tickets [5], registers [8]

Keepstone Ledger

Sample dataPublished 30 Aug 2026

Cloister School

Built 1911 · 4,200 m² · handed over Feb 2025

MeasureAgainst targetResultTargetRecord
Heat and power
Months of meter data121212 months to Aug 2026 · [1]
Heat demand removed61%55%Degree-day corrected · S&P · [1]
Heat from the heat pump96%100%Standby boiler ran 4% · [1]
Air leakage removed72%80%Blower door, 50 Pa · S&P · [2]
Fabric kept
Original fabric kept, by weight94%90%Retained-mass schedule · [3]
Windows repaired in place18821426 remade in oak · [4]
Wall test points dry3942Pin meter, Mar 2026 · [4]
Materials
Material reused or recycled81%90%Skip and pallet tickets · [5]
Carbon kept by not rebuilding1,210 t1,050 tFixed factor table · S&P · [3]
Air and comfort
Occupied hours under 1,000 ppm CO₂92%95%14 loggers, 5-minute · [6]
Occupied hours at 18–24 °C97%95%14 loggers, 5-minute · [6]
Money
Contract paid to us100%100%Holdback released Mar 2026 · [7]
Heating bill cut, a year£24,600£21,000Owner’s invoices · [7]

Readings to 31 Aug 2026 · checked by Sallow & Pike · [9]

How we measure

On site

Every reading is signed by a checker we don’t pay.

These three readings come from Cloister School’s ledger. Sallow & Pike take and sign each one, and the owner pays their fee directly.

  • A blower-door test fan sealed into a painted timber doorway at Cloister School.
    Main door, Cloister School · photographed Mar 2025 during the handover test

    Air leakage

    72%

    Air leakage removed, against an 80% target

    Blower door at 50 Pa, before works and at handover · Mar 2025 · checked by Sallow & Pike · [2]

  • A gloved hand pressing a moisture meter’s pins into patch-repaired lime plaster.
    Classroom 4, east range · photographed Mar 2026 at the twelve-month check

    Wall moisture

    39 of 42

    Wall test points dry, below 16% moisture

    Pin meter in lime plaster, fixed points · Mar 2026 · method by Aldmere Building Physics Lab · [4]

  • A small data logger clipped to an old oak roof beam beside a blank paper tag.
    Roof beam over the hall · photographed Sep 2025 when the loggers went up

    Indoor air

    92%

    Occupied hours under 1,000 ppm CO₂, against 95%

    14 loggers at 5-minute intervals · Sep 2025 – Aug 2026 · occupied hours only · [6]

The hall at Cloister School after works: oak roof trusses cleaned and repaired above lime-plastered walls, with low winter sun through the tall windows throwing long shadows across the floor.

Cloister School, the hall · oak trusses of 1911 repaired, insulation hidden above the boards · photographed Jan 2026

Carbon

A kept wall has already paid its carbon.

Knocking down and rebuilding spends carbon twice, once on demolition and again on new concrete and steel. We weigh the structure we keep and count what a new build would have emitted.

0 tsurvey estimate 3,000 t

Counted Aug 2026 · six buildings, 10,340 m² · retained mass multiplied by a fixed table of emission factors · checked by Sallow & Pike · [3]

Plans and terms

We are paid last, and by the meter.

Every contract has the same three parts. You pay for the survey when you book it and for the works as they happen. The last 15% waits until a year of meter readings meets the target.

  1. Survey

    For owners deciding whether a building is worth keeping.

    £4,800

    Fixed fee per building, paid on booking

    Sample fee

    • Six weeks of logging for heat, air and damp
    • A measured drawing set of the building
    • A draft target for the contract
    • The data stays yours if you stop here

  2. Works

    For owners who sign the target.

    Cost plus 12%

    Invoiced monthly against the building’s ledger

    • Repair and retrofit by our own crews
    • Every invoice line published in the ledger
    • Meter data from the day of handover
    • One named site lead from survey to sign-off

  3. Holdback

    Written into every contract we sign.

    15% of the contract

    Paid after twelve months of meter data meet the target

    • Yours to keep if the target is missed
    • Checked by Sallow & Pike, paid by you
    • Released or kept within 30 days of month twelve
    Share of each contract paid to us
    BuildingPaid against the contractShareRecord
    Lathe Barn100%Holdback released Jul 2023 · [7]
    Ferrier’s Mill100%Holdback released Dec 2024 · [7]
    Cooper’s Row85%Kept by the owners Apr 2025 · heat 47% against 50% · final · [7]
    Cloister School100%Holdback released Mar 2026 · [7]
    Colonnade Wing85%due Oct 2026 Twelve months closed Aug 2026 · sign-off pending · [7]
    Wellgate Pump House85%due Apr 2027 Five months metered · [7]
A woman in a linen work shirt adjusts the valve on a cast-iron radiator beside a classroom window.

Twelve months on

“For eleven winters we patched the boiler and hoped. The ledger is the first document about heating that our governors have read to the end.”

Ines Haverkamp, site steward, Cloister School

Said at the twelve-month review, March 2026. A fictional person; the portrait is a generated stand-in.

Pledges

Six pledges, each with a due date.

Furthest from done

Run every site van without diesel.

These are promises about how we run the practice, apart from any one building. Each stays an outline until a count or a register fills it, and none is rounded up.

0 of 9 vans

due Jun 2027 Counted Aug 2026 · three electric vans on order, delivery Feb 2027 · [8]

The other five, from furthest behind to done
PledgeCountAgainst the pledgeDue and record
Train 40 apprentices in lime, sash and timber repair.17 of 40due Dec 2027 Counted Aug 2026 · countersigned by the Lime & Sash Guild · [8]
Every building on our books runs on heat that burns no fossil fuel.5 of 10due Oct 2028 Counted Aug 2026 · Cloister School’s standby boiler is still connected · [8]
Publish each building’s meter data within 30 days of the month’s end.11 of 12due monthly Counted Sep 2025 – Aug 2026 · Feb 2026 went out late · [8]
Reuse or recycle 90% of what we remove, by weight, on every site.84%due at handover Weighed Jun 2022 – Aug 2026 · all six sites · [5]
Hand every owner the raw meter data along with our summary.6 of 6due at handover Counted Aug 2026 · handover files · [8]
The old dairy, an empty brick building with boarded lower windows, across a cobbled street at blue hour.

The old dairy, 1928 · 1,850 m² · photographed Sep 2026 at blue hour, before any work · contract signed Aug 2026

due Jun 2027

  • The building stays in use

    Loggers clip to walls and beams, and nothing is opened up during the survey

  • The survey data stays yours

    Logger files and drawings are handed over, even if you stop at the survey

  • Signed by a checker you pay

    Sallow & Pike sign every survey reading · [9]

Book a survey

Bring us the next building.

Tell us where it is. A Keepstone surveyor visits within 15 working days and logs the building for six weeks. You get a draft target before you sign anything.

first visit due within 15 working days

We reply within two working days, and your details stay with the survey desk.

Checked and backed by

  • [1]
  • [9]
  • [9]
  • [8]
  • [4]
  • [8]

Sources and methods

Every number we publish has a source.

Open a row to see how a figure was measured and who signed it off.

  • An outside checker on every figure

    Sallow & Pike, energy auditors, paid by each owner · [9]

  • Raw data goes to the owner

    6 of 6 owners hold their meter files · counted Aug 2026 · [8]

  • Misses stay on the page

    Cooper’s Row, heat 47% against 50%, holdback kept by the owners · [7]

  1. [1]Heat metersHalf-hourly heat meters · degree-day corrected to 2021–23 · checked by Sallow & Pike

    Every ledger carries the raw readings, and a figure that combines buildings is weighted by floor area. Each heat target is written into the contract once the survey ends, as a share of the heat demand the survey measured, and counts as met when twelve consecutive months of corrected readings reach it.

  2. [2]Airtightness testsBlower door at 50 Pa · before works and at handover · checked by Sallow & Pike

    We pressurise the whole building with a fan sealed into one doorway, once before works and once at handover. The share removed is the fall in leakage between the two tests.

  3. [3]Retained mass and emission factorsStructure weighed by element · one fixed factor table · checked by Sallow & Pike

    We weigh what stays standing from the survey drawings and site checks, then count what a new building of the same floor area would have emitted. The factors for masonry, timber, concrete, steel and glass were fixed before any building was counted.

  4. [4]Repair and moisture logPin meter at fixed wall points · under 16% counts as dry · signed by the owner

    The log holds one entry per window, door and room. Readings follow the Aldmere Building Physics Lab field method for pin meters in lime plaster, at the same marked points every time.

  5. [5]Waste and reuse weightsCarrier tickets for every skip and pallet · all sites · weighed off site

    Everything that leaves a site goes on a licensed carrier’s ticket with its weight. Reused and recycled weight is counted against the total removed.

  6. [6]Indoor air and temperatureCO₂ and temperature loggers · 5-minute intervals · occupied hours only

    Loggers sit on walls and roof beams, and occupied hours come from each owner’s timetable. A logger that drops out is marked in the ledger, and its missing hours stay blank.

  7. [7]Payments registerInvoices, holdbacks and heating bills · reconciled monthly with each owner

    The holdback is released or kept within 30 days of month twelve. Bill savings come from the owners’ own heating invoices.

  8. [8]Company registersHandover, heat source, fleet, apprentice and publication registers · counted monthly

    Registers close on the last working day of each month and are mirrored to the Fallowmere Register. A pledge moves only when its register moves: a van counts once it is on the fleet register, and an apprentice once the Lime & Sash Guild countersigns their final assessment.

  9. [9]Checkers and backersSallow & Pike, paid by each owner · Northfold Building Trust · Commons Retrofit Fund

    Sallow & Pike check every measured figure, and their fee does not move with our results. Northfold Building Trust funded the Cloister School survey, and Commons Retrofit Fund lends against the holdback. Both read the same ledgers as everyone else.