HOUSE EXTENSIONS · CHESHIRE
JNR Construction builds house extensions across Cheshire and south Greater Manchester — single-storey rear, double-storey, wraparound and kitchen extensions on substantial period and post-war homes. Every one is engineered before it is priced: load paths resolved, steelwork sized, Building Regulations and Party Wall obligations mapped, and the existing fabric protected through construction. One project manager, one point of accountability, from first survey to handover.
Most contractors treat a house extension as additional floor area. JNR Construction treats it as a structural engineering project. Every extension we build begins with a load path analysis — how the new structure will bear on the existing building, what steelwork is required to create the spans the design demands, and where temporary works are needed to protect the existing fabric during construction.
This distinction matters because the failure points in poorly executed extensions are almost never cosmetic. They are structural: undersized lintels, inadequately propped openings, cold bridges at junctions. We engineer these details out before ground is broken.
Every opening, span, and load-bearing alteration is engineered with appropriately specified steelwork — RSJs, flitch plates, and padstones — installed by our in-house structural team.
We assess Permitted Development eligibility, manage pre-application discussions with the Local Planning Authority, and handle Building Regulations submissions across Parts A, B, F, K, and L.
Period Cheshire properties demand precise material matching. We source reclaimed brick, natural stone, and traditional mortar mixes that satisfy Conservation Officers and satisfy the eye in equal measure.
An extension is not one job. The planning route, the structural problem and the services are different in each of the four briefs below, and those differences decide the programme and the budget far more than floor area does. All four are work we deliver across Cheshire and south Greater Manchester, under one project manager and a single point of accountability from first survey to handover.
The most common brief we take, and the one where the planning route matters most. Some single-storey rear extensions fall within permitted development and many do not; the test turns on depth and height, how much of the original curtilage is already built on, and whether the property sits in a conservation area or under an Article 4 direction. We settle that before design work goes far, because a scheme drawn to the wrong assumption is a scheme drawn twice.
Structurally the work concentrates in one place: the opening between old and new. Removing a rear wall transfers load onto a steel beam, and that beam needs bearings, padstones and a load path down to foundations able to take it. The other recurring constraint is below ground, where a drain crossing the footprint means a build-over agreement with United Utilities — a lead time rather than a formality.
Building at first floor changes the engineering and the planning argument at the same time. Foundations have to carry two storeys rather than one, which usually means deeper excavation and sometimes underpinning or a piled solution where the existing footings are shallow Victorian brick. The new roof has to tie into the original properly, because a badly formed valley is the detail that fails twenty years later.
On the planning side the questions become massing and neighbours: how far the addition projects past the building line, what it does to light and outlook, and whether it still reads as subordinate to the original house. On semi-detached and terraced properties the Party Wall etc. Act 1996 is a certainty rather than a possibility. We serve notices early, because a neighbour informed in good time is rarely the problem; one who finds out from a scaffolder is.
A wraparound is two extensions that have to behave as one. Wrapping side and rear means the structure turns a corner, and the corner is where the engineering concentrates: a goalpost frame of columns and beams carrying both the removed rear wall and the removed flank, with every connection designed rather than assumed.
Phasing is the other discipline. The existing roof, drainage and usually a working kitchen have to keep functioning while the footprint changes around them, so the sequence of temporary works matters as much as the permanent structure, and foul and surface water almost always need diverting. On a Wilmslow wraparound we installed heavy RSJs across both elevations and rebuilt the drainage before any finish went in. That is the right order, and it is not the order a programme written backwards from a completion date tends to produce.
Most clients arrive describing a kitchen rather than a structure, and they are usually right about what they want and reasonably unconcerned with how it gets built. A kitchen extension is a single-storey addition with a services problem attached: drainage, gas, water and a substantial electrical load all have to arrive in specific places, and those positions are fixed by a kitchen design that is often not finalised when the slab is poured.
We resolve the first-fix layout against the kitchen drawings before groundworks rather than after. Two other things are worth settling early. Large rooflights and sliding doors move the thermal and solar calculations under Part L, and an open-plan kitchen changes what Part F asks of extract ventilation. Both are considerably cheaper to design for than to retrofit. Our Design-to-Build process exists to catch exactly this.
Two things decide the programme on all four. The first is how much remains unknown when work starts: an opened-up floor, a trial hole or a drainage survey answers a question that would otherwise arrive later as a variation. The second is whether planning consent and Building Regulations approval are actually in place or still being chased, because a programme built around an assumed approval date carries one entirely unmanaged risk. We price from surveys rather than assumptions, and we tell you which assumptions are still open.
Under the Construction (Design and Management) Regulations 2015, domestic clients automatically transfer Principal Contractor duties to the contractor they appoint. JNR Construction formally assumes those duties on every qualifying extension project: we prepare and maintain the Construction Phase Plan, coordinate trade health and safety, and compile the Health and Safety File handed to you at practical completion.
This is not a legal technicality. It is the governance framework that keeps your site safe, your project on programme, and your position protected should any incident or query arise after the build. A contractor who does not operate under CDM 2015 is a contractor who is not running the project properly.
A structurally complex wraparound addition requiring heavy RSJ installation to achieve the client’s brief for a fully open rear aspect. The works involved removal of the original rear wall elevation, temporary propping of the existing roof structure, and installation of a twin-beam structural steel frame to carry the new load path. Bi-fold glazing runs the full width of the rear elevation. Masonry matched to the original 1930s brick. Part L insulation strategy incorporated throughout the new fabric.
We deliver house extensions across eighteen towns in Cheshire and south Greater Manchester, and the planning position is different in almost every one. An Article 4 direction governs materials and openings in Hale; Green Belt volume limits drive the design in Chelford; four conservation areas and a River Bollin flood warning area shape what is consentable in Wilmslow. Start with the town page for your address – Wilmslow, Knutsford, Macclesfield, Stockport, Altrincham or Northwich – or see the full list.
Many extensions fall within Permitted Development rights, which allow works to proceed without a formal planning application provided they meet the parameters set by the Town and Country Planning (General Permitted Development) (England) Order 2015. The key thresholds are: single-storey rear extensions up to 4 metres on detached properties (3 metres on other types under standard PD), no more than half the original garden area covered, and height restrictions on side and rear extensions.
However, properties in Conservation Areas, Areas of Outstanding Natural Beauty, or National Parks lose certain PD rights, and Article 4 Directions — applied by Cheshire East and Cheshire West in specific locations — can remove PD rights from individual streets or areas. We assess your property's position before any design is progressed.
The principal Parts are A (structural safety — foundations, steelwork, load paths), B (fire safety — escape routes if the extension alters the existing layout), F (ventilation of new habitable space), K (protection from falling — stairs, guarding), and L (thermal performance — insulation values for new walls, roof, and glazed elements, including the Part L conservation of fuel and power requirements).
In practice, Part A and Part L generate the most detailed engineering work on a complex extension. We manage the Full Plans Building Regulations submission, coordinate staged inspections with the Building Control Officer or an Approved Inspector, and obtain the final Completion Certificate on your behalf.
If your proposed extension involves excavation within 3 or 6 metres of an adjoining owner's building (depending on depth) or involves work on or at the boundary, the Party Wall etc. Act 1996 applies. You are required to serve a formal Party Wall Notice on all affected adjoining owners — typically two months before works commence for a Party Wall Award, less for excavation notices depending on the proximity. If an adjoining owner dissents, an agreed surveyor or two surveyors must produce a Party Wall Award documenting the condition of affected structures before works begin. We advise on whether the Act applies to your specific design and can recommend a Party Wall surveyor where required.
Yes — this is one of our primary project pathways. Where an architect or architectural designer has already produced a design and obtained planning consent, JNR steps in as the executing contractor. We review the drawing package, provide a buildability review at pre-construction stage, raise any ambiguities before work begins rather than improvising on site, and report progress against the programme. We do not value-engineer your architect's design without their explicit instruction.
Programme duration is a function of structural complexity, ground conditions, consent timescales, and specification level. As a general guide: a single-storey rear extension is typically 12–18 weeks on-site once all consents are in place; a double-storey addition 18–26 weeks; a complex wraparound with significant steelwork 24–32 weeks or more. These timings assume a clean start — they do not include the pre-construction period for Building Regulations approval or planning consent, which adds 8–12 weeks on average. We issue a detailed programme at pre-construction stage so you understand the full timeline from day one.
Whether you have a set of architect’s drawings or are still at the ideas stage, Julian will give you a straight assessment of what your project involves, what it will take to build properly, and what the regulatory requirements are. No obligation.
