Engineer's calculations for a By Brook project — steel beams sized, padstones and load paths worked out and a signed calculations package your builder and Wiltshire Council's building control can build from, delivered in days and revised free until it is approved.
Wiltshire Council granted 96% of the householder planning decisions it made in its latest published year — 9 points above the 87% England-wide householder average. By Brook contains BIDDESTONE, CASTLE COMBE, GRITTLETON conservation areas (BIDDESTONE designated 1973), so materials, fenestration and roof form are assessed against the appraisal, which is where a policy-literate drawing pack earns its keep. Its dominant Victorian (1837–1901) and postwar (1945–1970) housing stock sets the design brief on most streets.
The permitted-development ceilings are fixed: 40m³ of new roof volume for a terraced loft and 50m³ for a semi or detached house under Class B, plus a 3m single-storey rear extension on a terrace or 4m on a detached house under Class A. By Brook carries at least one Article 4 direction, and conservation areas including BIDDESTONE, CASTLE COMBE and GRITTLETON remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in By Brook is determined against an 8-week statutory target.
BIDDESTONE (conservation area designated in 1973), CASTLE COMBE (conservation area designated in 1973), GRITTLETON (conservation area designated in 1973), HULLAVINGTON AIRBASE (designated conservation area), LEIGH DELAMERE (designated conservation area), LITTLETON DREW (designated conservation area), LONG DEAN - FORD - SLAUGHTERFORD (designated conservation area), NORTH WRAXALL (designated conservation area), SEVINGTON (designated conservation area), UPPER WRAXALL (designated conservation area), WEST KINGTON (conservation area designated in 1975), YATTON KEYNELL (designated conservation area), Hullavington (civil parish within By Brook), Nettleton (civil parish within By Brook), North Wraxall (civil parish within By Brook), Biddestone and Slaughterford (civil parish within By Brook), Castle Combe (civil parish within By Brook) and Grittleton (civil parish within By Brook) — these are the By Brook pockets our drawings cover most. Heritage designations here include BIDDESTONE, CASTLE COMBE, GRITTLETON, HULLAVINGTON AIRBASE, LEIGH DELAMERE, LITTLETON DREW, LONG DEAN - FORD - SLAUGHTERFORD, NORTH WRAXALL, SEVINGTON, UPPER WRAXALL, WEST KINGTON and YATTON KEYNELL. Wiltshire Council weighs each proposal against Wiltshire Council's development plan and the design policies it applies to householder applications, where the 2,320 homes here are 35% pre-1900, 10% 1965-1972, 7% 1945-1954, which is what sets the realistic roof and rear-projection options. On roofs the borough is steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building, over Victorian and earlier houses (35% of 2,320 homes), late-1960s and early-1970s houses (10%) and early postwar houses (7%).
Before anything is drawn we check your address against the designations that apply in By Brook: BIDDESTONE (conservation area designated in 1973), CASTLE COMBE (conservation area designated in 1973), GRITTLETON (conservation area designated in 1973), HULLAVINGTON AIRBASE (designated conservation area), LEIGH DELAMERE (designated conservation area), LITTLETON DREW (designated conservation area), LONG DEAN - FORD - SLAUGHTERFORD (designated conservation area), NORTH WRAXALL (designated conservation area), SEVINGTON (designated conservation area), UPPER WRAXALL (designated conservation area), WEST KINGTON (conservation area designated in 1975) and YATTON KEYNELL (designated conservation area). Inside those boundaries permitted development is curtailed and Wiltshire Council assesses materials, window detail and roof form against the area's own appraisal, so a scheme that would be waved through two streets away can need a full application here.
Beyond the designated areas, By Brook takes in Hullavington, Nettleton, North Wraxall, Biddestone and Slaughterford, Castle Combe and Grittleton. Wiltshire Council has 48 recorded Article 4 directions, removing permitted development for rear and side extensions and other roof alterations, including rooflights — check the address before assuming PD applies in By Brook.
On stock, By Brook is Victorian and earlier houses (35% of 2,320 homes), late-1960s and early-1970s houses (10%) and early postwar houses (7%) — which is why steeply pitched slate roofs, valley gutters and party parapets typical of pre-1900 building and shallow-pitched roofs and integral garages typical of that period's building govern what a loft or rear projection can realistically be. Wiltshire Council decided 1,779 householder applications in the latest published year and granted 96%, with 53% issued inside the eight-week target. That decision record, not a national figure, is what we design to.
The full build-period split for By Brook runs pre-1900 35% (820 homes), 1900-1918 2% (50 homes), 1919-1929 0% (10 homes), 1930-1939 4% (100 homes), 1945-1954 7% (170 homes), 1955-1964 6% (150 homes), 1965-1972 10% (240 homes), 1973-1982 6% (140 homes), 1983-1992 7% (160 homes), 1993-1999 6% (130 homes) and 2000-2008 7% (160 homes). That distribution is why pre-1900 detailing dominates the drawings here, and it is measured from council-tax records rather than assumed from the street name.
Wiltshire Council also decides for Aldbourne & Ramsbury, Amesbury West, Avon Valley, Box & Colerne, Corsham Ladbrook, Corsham Pickwick, Corsham Without and Cricklade & Latton, so a decision in By Brook sits inside a wider pattern of decisions we track across the same authority — useful when an officer cites a precedent from the next area over.
The Article 4 directions recorded for this council include Ashley, Avebury, Baydon 1 and Baydon 2. Each removes a specific permitted-development right inside its own boundary, which is why the check is done on the address rather than on the town.
Published figures for By Brook and Wiltshire Council. These are the numbers that decide what is realistic on your street, so we work from them rather than from national averages.
| Measure | By Brook |
|---|---|
| Dwellings recorded | 2,320 |
| Built pre-1900 | 820 (35%) |
| Built 1900-1918 | 50 (2%) |
| Built 1919-1929 | 10 (0%) |
| Built 1930-1939 | 100 (4%) |
| Built 1945-1954 | 170 (7%) |
| Built 1955-1964 | 150 (6%) |
| Built 1965-1972 | 240 (10%) |
| Built 1973-1982 | 140 (6%) |
| Built 1983-1992 | 160 (7%) |
| Built 1993-1999 | 130 (6%) |
| Built 2000-2008 | 160 (7%) |
| Built before 1919 | 38% |
| Built 1919–1939 | 5% |
| Built 1945–2008 | 50% |
| Conservation areas in By Brook | 12 (BIDDESTONE, CASTLE COMBE…) |
| Conservation areas district-wide | 245 |
| Article 4 directions recorded | 48 |
| Householder applications decided | 1,779 |
| Householder applications granted | 96% |
| Decided within 8 weeks | 53% |
Dwelling stock from VOA council-tax data at 31 March 2025; conservation-area and Article 4 counts from planning.data.gov.uk (MHCLG); decision figures are Wiltshire Council's own, from MHCLG live table PS2 for the year to 31 March 2026.
The moment a wall comes out or a new floor goes in, something has to carry the load that wall or floor was holding — and building control will not accept "it looks strong enough". The engineer traces the load path: the weight of the roof, floors and walls above is gathered into a beam, the beam is sized in steel or timber to carry it within safe deflection, and that load is passed through padstones into the masonry and down to the ground. On By Brook's Victorian and earlier houses (35% of 2,320 homes), late-1960s and early-1970s houses (10%) and early postwar houses (7%), the spans and loads differ house to house, so every calculation is specific to the property.
The deliverable is two things that work together: the calculations, which show the maths an approved inspector can check, and the structural drawings, which turn that maths into something a builder can order and fit — a beam schedule with sizes and lengths, bearing and padstone details, and connection notes. By Brook contains BIDDESTONE, CASTLE COMBE, GRITTLETON conservation areas (BIDDESTONE designated 1973), so materials, fenestration and roof form are assessed against the appraisal, and the calculations are drawn to sit alongside the architectural set rather than contradict it. Everything is signed by a chartered or incorporated engineer carrying professional indemnity insurance.
Older By Brook stock — the kind found across BIDDESTONE, CASTLE COMBE, GRITTLETON, HULLAVINGTON AIRBASE, LEIGH DELAMERE, LITTLETON DREW, LONG DEAN - FORD - SLAUGHTERFORD, NORTH WRAXALL, SEVINGTON, UPPER WRAXALL, WEST KINGTON and YATTON KEYNELL — often hides the real structural question: shallow Victorian foundations, timber that has been notched by past work, or a wall that turns out to be load-bearing when the drawings assumed otherwise. Wiltshire Council has 48 recorded Article 4 directions, removing permitted development for rear and side extensions and other roof alterations, including rooflights — check the address before assuming PD applies in By Brook. A survey-based calculation catches this before the wall is opened, not after.
Building control needs an engineer's calculations whenever you change how the building carries load. On a typical By Brook project that means any of these:
We size the steel, work the padstones and bearings, trace the load to the foundations and issue a signed calculations package and a beam schedule for Wiltshire Council's building control — coordinated with your architectural drawings so the beam that is calculated is the beam that is drawn and the beam that is ordered.
Below is Wiltshire Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Wiltshire Council granted 96% of its householder applications in the year to 31 March 2026, and BIDDESTONE shapes what is approved here. Structural calculations sit behind building control rather than planning, but the same wave of loft, extension and knock-through work that drives these decisions is exactly what needs an engineer's package.
Source: MHCLG planning application statistics (householder decisions, England, 1 April 2025 - 31 March 2026). Compare every borough on our London approval-rate league table.
Tell us about your project and get a fixed, no-obligation quote back within one working day. If you don't need planning permission at all, we'll tell you that too — for free.
Building control approves structural work by checking the numbers, not by looking at the finished steel. Wiltshire Council's inspector, or an approved inspector acting for you, reads the calculations to confirm the beam is deep enough for its span, that deflection stays within limits so ceilings do not crack, that the bearing length and padstones spread the point load into masonry that can take it, and that the load has somewhere to go all the way to the ground. Across BIDDESTONE, CASTLE COMBE and GRITTLETON, the recurring issue is a beam sized off a rule of thumb that the actual span will not support.
The 2,320 homes here are 35% pre-1900, 10% 1965-1972, 7% 1945-1954, which is what sets the realistic roof and rear-projection options. We issue calculations detailed enough to be signed off without a query, coordinate them with the architect's drawings so nothing conflicts on site, and stay available to revise if the builder finds the By Brook property is not quite as the survey assumed — free, until the work is approved.
We calculate beams, openings and floors on the period and modern stock across the borough. A few of the By Brook neighbourhoods where structural packages come up most often:
Structural calculations for BIDDESTONE's conservation area designated in 1973 — beams sized, load paths traced and signed for Wiltshire Council's building control.
Structural calculations for CASTLE COMBE's conservation area designated in 1973 — beams sized, load paths traced and signed for Wiltshire Council's building control.
Structural calculations for GRITTLETON's conservation area designated in 1973 — beams sized, load paths traced and signed for Wiltshire Council's building control.
Structural calculations for HULLAVINGTON AIRBASE's designated conservation area — beams sized, load paths traced and signed for Wiltshire Council's building control.
Structural calculations for LEIGH DELAMERE's designated conservation area — beams sized, load paths traced and signed for Wiltshire Council's building control.
Structural calculations for LITTLETON DREW's designated conservation area — beams sized, load paths traced and signed for Wiltshire Council's building control.
Different jobs load the building differently, so each needs its own calculation. This is what the common By Brook projects typically require.
| Project | Typical structure | What the calculation proves | Signed off by |
|---|---|---|---|
| Wall knock-through | Steel beam on padstones | Span, deflection and bearing | Building control |
| Loft conversion | New floor beams and ridge/purlin steels | Floor loading and roof support | Building control |
| Rear or side extension | Opening beam plus extension roof and floor | Combined loads and foundations | Building control |
| Basement or underpinning | Retaining and foundation design | Ground and adjacent-building loads | Building control & party wall |
On older By Brook stock around BIDDESTONE and CASTLE COMBE, shallow foundations and altered structure often mean the calculation drives the design rather than following it.
A fixed process built around building control rather than planning — most calculation packages are ready within five days of the architectural drawings.
Send us your By Brook postcode and the architect's drawings or a sketch. We confirm what structure the project needs, flag any load-bearing wall or foundation question, and tell you exactly what the calculation package will cover.
Where the loads are not obvious — an unknown wall, an old alteration, a deep span — we survey the property so the beam is sized on what is really there, not an assumption.
A chartered or incorporated engineer sizes the steel, works the padstones and load path, and issues the signed calculations and a beam schedule coordinated with your By Brook architectural set.
We submit the calculations to Wiltshire Council's building control or your approved inspector, answer queries, and revise free if the build uncovers something the survey could not see.
Whenever you change how the building carries weight — removing or opening a load-bearing wall, converting a loft, building an extension, or inserting a beam or column. Wiltshire Council's building control needs an engineer's calculation to approve any of these before the steel goes in. A By Brook project that only redecorates or moves a non-structural partition does not, but almost anything that opens the structure does.
No — they are a separate, later step. Planning permission decides whether Wiltshire Council will allow the change; structural calculations prove the change is safe to build and are submitted to building control, not to the planners. Many By Brook projects that need no planning permission at all — an internal knock-through, a permitted-development loft — still need a full engineer's calculation before work can lawfully start.
A chartered or incorporated structural engineer, carrying professional indemnity insurance, who takes responsibility for the numbers. Wiltshire Council's building control, or an approved inspector acting on your behalf, then checks and signs them off. Your builder cannot self-certify a steel beam, and an unsigned calculation will not be accepted — the engineer's signature and insurance are what make the package one building control will approve. This applies to your By Brook address specifically.
Yes — a beam over a removed wall is the most common calculation we do. We work out the load the wall was carrying, size a steel or timber beam to span the opening within safe deflection, and detail the padstones that spread its weight into the masonry each side. The result is a beam schedule your By Brook builder can order and Wiltshire Council's inspector can approve, with the load traced all the way to the foundations.
Sometimes. Where the loads are clear from the drawings we can calculate directly, but By Brook's older stock often hides surprises — a wall that turns out to be load-bearing, notched or altered joists, or shallow foundations near BIDDESTONE and CASTLE COMBE. In those cases a short structural survey means the beam is sized on what is really there, which avoids a redesign once the builder opens the wall. Wiltshire Council is the decision-maker.
We price each By Brook package on the number of beams and the complexity — a single knock-through is straightforward, a whole-house loft-and-extension scheme has several elements — and send a fixed, no-obligation quote within one working day. It covers the calculations, the beam schedule and free revisions until Wiltshire Council's building control approves. Call 020 7864 7245 to start.
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