Engineer's calculations for a Old Portsmouth project — steel beams sized, padstones and load paths worked out and a signed calculations package your builder and Portsmouth City Council's building control can build from, delivered in days and revised free until it is approved.
Portsmouth City Council granted 88% of the householder planning decisions it made in its latest published year — 1 point above the 87% England-wide householder average. Old Portsmouth is the city's original walled settlement, so alterations are measured against surviving Georgian and pre-Georgian fabric, which is where a policy-literate drawing pack earns its keep. Its dominant Georgian (1714–1837) housing stock sets the design brief on most streets.
Before permission is required, Class B allows 40m³ of added loft volume on a terrace and 50m³ on a semi or detached house, and Class A allows a 3m single-storey rear extension on a terrace or 4m on a detached house. Old Portsmouth carries at least one Article 4 direction, and conservation areas including Old Portsmouth and Gunwharf remove those rights outright, so we confirm your exact address before a line is drawn. A validated householder application in Old Portsmouth is determined against an 8-week statutory target.
The Point (cobbled Spice Island lanes of historic cottages by the harbour mouth), High Street (Georgian town houses around the Cathedral), Broad Street (the narrow spine down to the Round Tower and Point), Grand Parade (formal Georgian frontages beside the fortifications), Gunwharf (the former ordnance yard, now waterfront apartments and quays) and Old Portsmouth Ramparts (houses set against the Hotwalls and sea defences) — these are the Old Portsmouth pockets our drawings cover most. Heritage designations here include Old Portsmouth and Gunwharf. Portsmouth City Council weighs each proposal against the Portsmouth Local Plan and the council's Houses in Multiple Occupation SPD, where the tight historic street pattern leaves almost no room to extend outward, concentrating change on roofs and rear yards. Much of Gunwharf and parts of the old town are flats and apartment conversions, which carry no householder permitted-development rights.. On roofs the borough is pitched tile and slate roofs on the town houses and parapet roofs on the taller Georgian frontages, over Georgian and Georgian-revival town houses, historic cottages around The Point and waterfront apartment conversions.
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 Old Portsmouth's Georgian and Georgian-revival town houses, historic cottages around The Point and waterfront apartment conversions, 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. Old Portsmouth is the city's original walled settlement, so alterations are measured against surviving Georgian and pre-Georgian fabric, 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 Old Portsmouth stock — the kind found across Old Portsmouth and Gunwharf — 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. Portsmouth's city-wide Article 4 direction removes permitted-development rights for small HMO conversions here as well, and in the historic core of Old Portsmouth even minor external works are tightly controlled by conservation-area policy. 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 Old Portsmouth 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 Portsmouth City 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 Portsmouth City Council's real householder decision record, drawn from official planning statistics and refreshed as new data lands. Portsmouth approves a healthy share of householder work in Old Portsmouth, but the historic core's Georgian fabric and cramped plots make heritage sensitivity the decisive factor. 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. Portsmouth City 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 The Point, High Street and Broad Street, the recurring issue is a beam sized off a rule of thumb that the actual span will not support.
The tight historic street pattern leaves almost no room to extend outward, concentrating change on roofs and rear yards. 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 Old Portsmouth 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 Old Portsmouth neighbourhoods where structural packages come up most often:
Structural calculations for The Point's cobbled Spice Island lanes of historic cottages by the harbour mouth — beams sized, load paths traced and signed for Portsmouth City Council's building control.
Structural calculations for High Street's Georgian town houses around the Cathedral — beams sized, load paths traced and signed for Portsmouth City Council's building control.
Structural calculations for Broad Street's the narrow spine down to the Round Tower and Point — beams sized, load paths traced and signed for Portsmouth City Council's building control.
Structural calculations for Grand Parade's formal Georgian frontages beside the fortifications — beams sized, load paths traced and signed for Portsmouth City Council's building control.
Structural calculations for Gunwharf's the former ordnance yard, now waterfront apartments and quays — beams sized, load paths traced and signed for Portsmouth City Council's building control.
Structural calculations for Old Portsmouth Ramparts's houses set against the Hotwalls and sea defences — beams sized, load paths traced and signed for Portsmouth City Council's building control.
Different jobs load the building differently, so each needs its own calculation. This is what the common Old Portsmouth 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 Old Portsmouth stock around Old Portsmouth and Gunwharf, 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 Old Portsmouth 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 Old Portsmouth architectural set.
We submit the calculations to Portsmouth City 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. Portsmouth City Council's building control needs an engineer's calculation to approve any of these before the steel goes in. A Old Portsmouth 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 Portsmouth City 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 Old Portsmouth 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. Portsmouth City 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 Old Portsmouth 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 Old Portsmouth builder can order and Portsmouth City 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 Old Portsmouth's older stock often hides surprises — a wall that turns out to be load-bearing, notched or altered joists, or shallow foundations near Old Portsmouth and Gunwharf. 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. Portsmouth City Council is the decision-maker.
We price each Old Portsmouth 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 Portsmouth City Council's building control approves. Call 020 7864 7245 to start.
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