07834 989360 Mon–Fri, 8am–5pm - AboutServicesAreasOur WorkReviewsContact07834 989360Request an Estimate Home/ - Areas we cover/ - Builders in Dartford Dartford · Rated 5.0 on Google # Double storeyextensionsin Dartford Adding a bedroom above a new ground-floor room is often the most cost-effective way to grow a Dartford family home. We handle the structural design, the planning route and the build. Request an estimate07834 989360 Written, itemised estimate after a survey, no obligation to proceed. 30 yearsof construction experience across the team CABE membersprincipals are members of the Chartered Association of Building Engineers 5.0 starsrated 5.0 from 14 Google reviews One point of contactdesign coordination, planning, procurement, build and supervision under one contract Building in Dartford ## We work in Dartford, and we know its houses Dartford is comfortably within our working area, reached from our office at Onega House, 112 Main Road, Sidcup, DA14 6NE. Surveys and site visits are arranged Monday to Friday, 8am to 5pm. The town mixes Victorian and Edwardian terraces near the centre with large inter-war and post-war suburban estates and a significant amount of newer development. Family houses on the estates typically have the plot width and garden depth for a two-storey extension, which is why more of our Dartford enquiries are for double-storey work than in the tighter areas closer to London. The older stock near the centre is a different job entirely: solid or early cavity walls, original roofs, and terraced access constraints that dictate how materials and steel arrive. We survey and design each property individually rather than assuming the postcode tells us what we are working with. The requests we get most are double-storey extensions adding a bedroom and bathroom, single-storey rear extensions to open up kitchens, loft conversions, structural openings on the ground floor, and whole-house refurbishment after a purchase. Two-storey work almost always needs a full planning application and careful structural design where it ties into the existing roof and foundations. All of that is detailed and coordinated before we price the build. Every Dartford project runs through the same five stages: design, planning and preparation, procurement, construction and project supervision, all managed under one contract by a team with 30 years of experience, with principals who are members of the Chartered Association of Building Engineers. You can request an estimate or read more about how we work. ## Get an estimate in Dartford Send us the details and we'll be in touch during working hours, Mon–Fri, 8am–5pm. Services in Dartford ## What we build in Dartford ### Home Extensions Single-storey, double-storey and wraparound extensions, design coordinated and built by one team. Home extensions in Dartford ### Loft Conversions Turn unused roof space into a bedroom, en-suite or office, structurally sound and building-control signed off. Loft conversions in Dartford ### New Build Homes Individual new build homes delivered from design package through to completion. New build homes in Dartford ### Full Refurbishments & Renovations Whole-house refurbishment, kitchens, bathrooms and period property renovation, managed end to end. Refurbishments & renovations in Dartford ### Internal Alterations Knock-throughs, new openings, reconfigured layouts and structural steels installed safely. Internal alterations in Dartford ### Outbuildings & Garden Rooms Insulated garden rooms, home offices, gyms and garages built to last all year. Outbuildings in Dartford ### Architectural Drawings & Design Coordination Survey, concept, planning and construction drawings coordinated with our recommended architects, ready to build from. Drawings & design in Dartford ### Structural Works Steels, foundations, load-bearing alterations and structural repairs. Structural works in Dartford ### Carpentry & Joinery First and second fix carpentry, roof structures, staircases and fitted joinery. Carpentry in Dartford ### Brickwork Extensions, garden walls, repointing and matched brickwork on period properties. Brickwork in Dartford ### Roofing Pitched and flat roofing, dormers, leadwork and roof coverings on new and existing homes. Roofing in Dartford ### Electrical, Plumbing & Gas Coordinated through vetted, accredited subcontractors: NICEIC/NAPIT registered electricians and Gas Safe engineers. Electrical & plumbing in Dartford Why Ashcroft ## Why homeowners in Dartford choose us ### Structural design coordinated for you Two-storey work is detailed by our recommended engineers and reviewed by principals who are members of the Chartered Association of Building Engineers, before the build is priced. ### Planning route confirmed early Double-storey extensions almost always need a full application. We tell you which route applies at survey stage rather than after design fees are spent. ### 30 years of experience 30 years of construction experience across the team, on residential extension, loft and refurbishment projects. ### Rated 5.0 on Google 5.0 stars from 14 Google reviews, from clients citing clear communication and high standards. ### Turn-key delivery Design, planning and preparation, procurement, construction and project supervision are all managed by one team. ### Accredited electrics and gas NICEIC or NAPIT registered electricians and Gas Safe registered engineers carry out and certify that work. Local property issues ## What we typically find on Dartford properties ### Existing foundations under new load Building a storey above an existing ground floor or garage puts new load onto old footings. Those foundations have to be exposed and assessed before any design is committed. ### Roof tie-ins that leak The junction where a two-storey extension meets the existing roof is the highest-risk detail on the build. Valleys, flashings and abutment upstands decide whether it stays dry. ### Ground conditions and mature trees Shrinkable ground and mature trees on the suburban estates around Dartford affect foundation depth. This is set from the survey rather than a standard detail. ### Party wall matters on semis Two-storey work on a semi-detached house almost always engages the party wall, so notices and procedures are identified at the start of the project. None of this is unusual, and none of it is a reason not to build. It is the reason we survey before we design and design before we price, so what turns up in Dartford is in the estimate rather than in a mid-build conversation about extra cost. How it works ## Five stages, all managed under one contract - 01 ### Design We take your brief, survey the property and coordinate the drawings and design package with our recommended architects and engineers, so you have no separate consultants to find or brief. - 02 ### Planning & preparation Applications, building control and the programme of works are prepared and coordinated before anyone lifts a tool. - 03 ### Procurement Materials and vetted trades are secured against a fixed scope, so the build starts with everything in place. - 04 ### Construction Your build is delivered by skilled tradesmen working to the agreed drawings, programme and standard. - 05 ### Project supervision A named point of contact supervises the site, handles building control and keeps you updated to completion. Dartford questions ## Frequently asked questions Do you cover Dartford?+Yes. Dartford is within our regular working area, served from our office at Onega House, 112 Main Road, Sidcup, DA14 6NE. How quickly can you get to Dartford?+Site visits and surveys are arranged during working hours, Monday to Friday, 8am to 5pm, from our Sidcup base. What does a double-storey extension cost in Dartford?+It depends on footprint, the condition and depth of existing foundations, structural steel, roof tie-in and internal specification. We survey and issue a written estimate with the scope itemised. Do I need planning permission for a two-storey extension?+Almost always, yes. We assess your property at survey stage, confirm the route, and prepare and coordinate the application. Can you build above an existing garage?+Sometimes: it depends entirely on the existing foundations and walls, which we expose and assess before designing anything. How long does the work take?+Design and planning come first, then construction. A written programme for your specific project comes with the estimate. Do you do emergency work in Dartford?+No. We deliver planned design-and-build projects rather than emergency repairs. Which nearby areas do you cover?+Crayford, Bexley, Bexleyheath, Sidcup, Welling, Blackfen and the wider Kent area. Rated 5.0 from 14 reviews ## What our clients say “Adam, Robbie and the team were fantastic delivering our kitchen extension and bathroom, great communication throughout and happy to adjust the design as we went.”Peter TingayKitchen extension & bathroom“Adam and Rob's team did an amazing job on our extension, from start to finish they made the process straightforward and painless.”Keith WeirHome extension“Professional, friendly and did a wonderful job creating a new opening between rooms in our Victorian home. Adam communicated clearly throughout. Highly recommend.”Holly MillsStructural opening Coverage ## Areas near Dartford we also serve Builders in BexleyBuilders in KentBuilders in SidcupBuilders in CrayfordAll areas we cover Alongside Dartford we work across Crayford, Bexley, Sidcup, Kent and the wider Kent and South East London area from our office at Onega House, 112 Main Road, Sidcup, Kent, DA14 6NE. If you are not sure whether your postcode is covered, contact our Sidcup builders and we will tell you straight away. You can also see examples of our work or start from our home page. ## Planning work in Dartford? Tell us about the property and what you want to achieve, or call 07834 989360. Request an estimate07834 989360 Extension, loft conversion and refurbishment specialists based in Sidcup, working across London, Kent and the surrounding areas. 5.0 from 14 Google reviews Facebook - Instagram ## Services Home extensions - Loft conversions - New build homes - Refurbishments & renovations - Internal alterations - Outbuildings - Drawings & design - Structural works ## Areas we cover - Bexley - Kent - South East London - Welling - Sidcup - Bexleyheath - Dartford - Crayford - Blackfen ## Get in touch - 07834 989360 - info@ashcroftconstructiongroupltd.co.uk - Onega House, 112 Main Road, Sidcup, Kent, DA14 6NEMonday8am – 5pm Tuesday8am – 5pm Wednesday8am – 5pm Thursday8am – 5pm Friday8am – 5pm SaturdayClosed SundayClosed © 2026 Ashcroft Construction Group Ltd. All rights reserved. ReviewsCookie policyPrivacy policyTerms & conditionsPrincipals are members of the Chartered Association of Building Engineers (CABE). 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