16 Vivian Road, Bow Mansard & Wraparound Extension
Project overview
The Project
A property investor appointed AC Design Solution to transform a four-bedroom terraced house in Bow into a high-end five-bedroom home for resale. The instruction was simple: use our expertise to maximise every usable part of the property without compromising how the finished house would function.
The existing house provided approximately 140 m² of gross internal area. Our approved design adds around 73 m² through a lower-ground-floor wraparound extension, a first-floor rear-outrigger extension and a new mansard roof, increasing the property to approximately 213 m² GIA.
Our house extension drawings did more than add floor area. They reorganised the property around its unusual relationship with the street and rear garden, turning the lower-ground floor into the principal everyday living level.
AC Design Solution was appointed from the outset. Our role covered the measured survey, architectural design, planning application, conservation-area response, structural engineering, Building Regulations, Party Wall surveying, construction support, site inspections and CDM Principal Designer duties.
Planning permission was secured under reference PA/25/02052/NC, and construction commenced in May 2026.
Drawings and project imagery
Project Gallery
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Selected architectural drawings, technical details and project views from the coordinated design package.
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Planning strategy
Planning & Heritage
The property is a mid-terrace house within the Driffield Road Conservation Area. The combination of front dormers, a mansard roof and substantial rear additions required a full planning application.
Our mansard loft conversion drawings proposed two front dormers and two rear dormers within a 70/30-degree dual-pitch mansard. Separating the dormers avoided one oversized opening and produced a roof composition that responded more closely to Tower Hamlets’ conservation guidance.
The approved mansard maintains an approximate 900 mm setback from the party walls and an approximate 1,100 mm setback to the front dormer faces. The proposed materials included natural Welsh slate, lead-clad dormers and traditional detailing appropriate to the conservation area.
The original design used a straighter rear roof form, similar to an existing adjoining mansard. During the application, the planning officer asked for the butterfly-roof form to be retained. We redesigned the roof around that requirement while preserving the proposed bedroom and bathroom within the new mansard.
This is a practical example of the additional design control that can apply to mansard loft conversions in conservation areas. The revised roof was not simply made smaller; its geometry was reconsidered so the conservation requirement could be met without undermining the client’s accommodation brief.
We also proposed reinstating the missing front cornice and parapet band from the start of the project. This repaired an incomplete section of the façade and restored a stronger visual relationship with the adjoining terrace. A financial contribution towards local streetscape improvements was also secured through a unilateral undertaking.
The planning officer concluded that the extensions were acceptable in scale, form and material treatment. No public objections were received, and the assessment found no unacceptable effect on the privacy, daylight, outlook or living conditions of the adjoining occupiers.
For another developer-led roof extension involving a more difficult planning strategy, see our Old Manor mansard loft conversion.
Spatial design
Architectural Design
The relationship between the street entrance and the rear garden drove the internal layout.
From Vivian Road, the entrance appears to be at ground-floor level. At the rear, however, this floor is raised considerably above the garden. The existing lower-ground floor therefore had the strongest natural relationship with the external space, but it did not function as the main living level.
Rather than treating it as a secondary basement, we reorganised the house so the lower-ground floor became the principal everyday living space.
The wraparound extension creates an open-plan kitchen, dining and family area, while retaining a separate reception room elsewhere in the house. A wide glazed opening connects the new living space with the rear patio and allows the internal and external areas to operate together.
The previous patio was approximately 1.5 metres deep and functioned mainly as a narrow space between the house and the raised garden. We increased it to approximately 3.5 metres and redesigned the garden steps to create a usable external terrace.
This was not an extension added onto an unchanged plan. The internal rooms, external levels, patio depth and garden access were redesigned as one arrangement so that the lower-ground floor felt like the centre of the house rather than a basement below it.
The upper floors were also reorganised to increase the accommodation from four bedrooms to five double bedrooms. The revised layout includes an en-suite bedroom at first-floor level and a further bedroom and bathroom within the mansard.
The completed arrangement provides five double bedrooms, two en-suite bedrooms, a retained family bathroom, a separate lower-ground-floor WC, an open-plan kitchen–dining–family space and a separate reception room. The planning drawings record the progression from the existing compartmentalised layout to the extended living floor and additional upper-level accommodation.
Engineering coordination
Structural Engineering
Opening the lower-ground floor into one continuous kitchen, dining and family space required more than a standard beam across the rear extension.
Our structural calculations and drawings introduced two bespoke cranked steel box frames. These use UC columns, heavy UC beams and concrete-encased ground beams to transfer loads around the open-plan layout without introducing new internal masonry walls.
One frame uses UC254×254×73 beams with UC203×203×46 columns. The heavier frame uses UC254×254×107 beams with UC203×203×60 columns.
The upper members are cranked to follow the slopes of the proposed extension roofs. This allows the main structure to sit within the architectural form rather than creating a deep horizontal beam below the finished ceiling.
The steelwork package includes bespoke end plates, stiffeners, bolted connections and full-penetration welded joints. Because the frames are being installed within an existing terraced house, the cranked dimensions are to be checked against the actual site levels before fabrication.
New trench foundations measuring 600 mm wide by 1,000 mm deep were designed for the extension. The new foundations are connected to the existing foundations using top-and-bottom reinforcement, helping the old and new construction work together.
The enlarged patio also required a 200 mm reinforced-concrete retaining wall to support the raised garden behind it. This retaining structure was essential to the architectural strategy because the deeper patio could not be created without safely supporting the higher ground level.
At roof level, the mansard uses a steel ridge beam and three UC152×152×37 supporting beams, combined with C24 timber joists, rafters, dwarf walls and inclined mansard framing. The system was coordinated with the retained butterfly roof, four dormers, staircase and bathroom layout.
Technical compliance
Building Regulations
Following planning approval, we prepared full Building Regulation drawings for the lower-ground extension, first-floor rear addition, mansard, internal alterations and associated structural works.
The external masonry wall build-up was developed to achieve a U-value of 0.18 W/m²K, while the pitched-roof build-ups achieve 0.15 W/m²K.
The fire drawings establish the required REI30 and REI60 construction zones through the altered house. Fire protection to the new steelwork, the stair enclosure and the mansard accommodation was coordinated against the actual structural arrangement rather than added as a separate specification exercise.
The construction package also coordinates:
- below-ground waterproofing around the lower-ground extension;
- damp-proof membranes and cavity trays;
- threshold drainage beside the glazed opening;
- insulation around the structural frames;
- fire protection to the steelwork;
- vapour-control and breather membranes;
- pitched-roof ventilation;
- retaining-wall and floor junctions;
- and the relationship between the patio, internal floor and external ground levels.
Each junction was developed against the actual wall positions, structural members, external levels and internal dimensions at Vivian Road, ensuring that the architectural and engineering packages remained coordinated through construction.
Neighbouring property matters
Party Wall
AC Design Solution also acted as the client’s Party Wall surveyor, allowing the statutory process and technical design to be considered together rather than in sequence.
At planning stage, the lower-ground extension wall was proposed astride the boundary with No. 14 Vivian Road.
When the wall, boundary and adjoining garden steps were examined in greater detail, it became clear that constructing it in the proposed position would require a substantial part of the neighbour’s steps to be ground back. This would have narrowed their access, increased the cost and complexity of the work and created disruption without producing a meaningful benefit.
We therefore redesigned the extension wall so that it sat wholly on the building owner’s land.
The wall build-up was reconfigured at the same time so that it continued to achieve the required 0.18 W/m²K thermal performance without reducing the proposed internal area. The neighbour’s steps were protected, unnecessary cutting was avoided and the client retained the GIA achieved through the wider design.
The construction-package revision history records a Party Wall update on 15 May 2026 and the revised wall position beside No. 14 on 18 May 2026. Dedicated Party Wall plans and sections were then prepared for the interfaces with both No. 14 and No. 18.
The relevant Party Wall notices covered the proposed boundary wall, excavation close to the adjoining structures and works affecting the existing party structure. We also prepared the Schedule of Condition internally and issued the documentation by post and email.
An adjoining property had previously constructed its own mansard and raised the shared wall. Because the new mansard at No. 16 enclosed upon and benefited from that existing work, we calculated the appropriate contribution for the use of the previously constructed wall.
This type of payment is separate from the surveyors’ professional fees and is assessed according to the benefit received from the existing work. Our guide to Party Wall Award costs and enclosure contributions explains how these costs arise.
The Party Wall process produced a measurable design outcome at Vivian Road: the adjoining owner’s steps were protected, unnecessary construction was avoided, the required U-value was maintained and the client retained the proposed internal floor area.
Consent and delivery
Project Outcome
The project increases the property from approximately 140 m² to 213 m² GIA, adding around 73 m² of accommodation.
The original four-bedroom house has been redesigned to provide:
- five double bedrooms;
- two en-suite bedrooms;
- a retained family bathroom;
- a separate lower-ground-floor WC;
- an open-plan kitchen, dining and family area;
- a separate reception room;
- an enlarged rear patio;
- and a direct relationship between the main living floor and the raised garden.
The design also reinstates a missing element of the front façade, retains the characteristic rear butterfly roof and resolves a difficult boundary relationship without sacrificing the client’s proposed internal area.
Planning, architectural design, structural engineering, Building Regulations and Party Wall work were not treated as separate packages. Retaining the butterfly roof, moving the boundary wall, reconfiguring its thermal build-up, retaining the raised garden and introducing two cranked steel frames were all decisions made against the same coordinated project information.
Construction commenced in May 2026, with AC Design Solution continuing to provide construction support, site input and CDM Principal Designer services.
For a mansard, wraparound extension or whole-house refurbishment requiring architectural, structural and Party Wall coordination, get in touch to discuss your property and proposed works.
