Extension · Conversion · Storey addition · Rhineland
Extension, conversion, storey addition — is it possible on your house?
Tell us what you have in mind — we tell you honestly whether it works, what it costs and how we get it approved. With a conversion the first question is whether it holds and gets through the building authority: that is engineering work. Design, structural engineering, building physics and site management come from one hand — one point of contact.
Fixed-price corridor
depending on the scale of the project, the procedure and the depth of construction management.
The fastest way
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No five questions, no form. Your name and number are enough — we will get back to you, usually the same working day.
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Disziplinen unter einem Dach
Konzept · Tragwerk · Bauphysik · GEG-Nachweise · CO₂-Bilanz · Bauleitung
Partnerbüros
AKNW-Architekt · Tragwerks-, Energie- und DGNB-Partner im Netzwerk
LP 4 · Bauantrag
Genehmigungsplanung in Kooperation mit AKNW-Partner-Architekt
Erfahrung
10 Jahre Profession · 70+ Bauvorhaben · Konzept bis Bauleitung
The substance-before-design method · 5 steps
From the extension idea to handover of the keys.
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On-site appointment
Survey of the existing building, capturing your wishes, a first procedural assessment (§ 62 / building application), checking dimensions.
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Variant study
Two to three extension variants with a sketch, a BKI cost estimate and a funding note. The client chooses the preferred variant.
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Permit-planning preparation
The complete building-application documents in technical form: site plan, floor plans, sections, elevations — handed to the AKNW partner for LP 4.
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Structural engineering & building physics
Structural design for the extension and the interfaces with the existing building, GEG certificate, thermal-bridge calculation and, where relevant, sound insulation.
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Construction management
Execution planning, tendering, on-site supervision by Robin Henn — a single point of contact throughout.
Anfrage · 5 Schritte
Direkt zu uns — Anfrage in 30 Sekunden.
Der schnellste Weg zu uns: fünf Fragen, eine pro Schritt. Antwort persönlich von Robin Henn binnen 24 Stunden.
Seven questions before the first building application.
Procedural exemption, BauO NRW limits, existing-structure analysis, GEG certificate — we settle the answers before you plan.
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01 Extension exempt from procedure under § 62 BauO NRW — when does that apply?
For single-storey extensions without habitable rooms and up to 75 m³ of gross volume, § 62 BauO NRW provides exemption from procedure. As soon as habitable rooms are created (living room, study, bedroom) or the 75 m³ limit is exceeded, a building application is required — which we submit through our AKNW partner architect. We clarify the procedural question before planning begins. -
02 Conservatory or extension — what is the difference?
A conservatory is a glazed, unheated extension for seasonal use — under building law it often counts as an ancillary structure. An extension with a habitable function (heated, in permanent use) is accounted for like living space: energy performance certificate, GEG certificate, fire-protection separation distances. The fixed-price corridor differs accordingly. -
03 Adding a storey on an existing roof — is it structurally feasible?
That depends on the existing load-bearing structure. We assess the timber-joist or solid ceiling, bearing certificates, the load capacity of the walls in the storey below and, where relevant, foundation reserves. In many houses from the 1960s to 1980s a lightweight timber storey addition is feasible, often combined with a building-physics upgrade. Preliminary structural assessment €1,785 gross, after which a fixed-price corridor applies for the overall planning. -
04 Converting a garage into living space — what is required?
A change of use from garage to habitable room requires a building permit (§ 60 BauO NRW), even if the shell remains. Required are: a GEG certificate, a fire-protection concept (the transition from wall to living space), a ventilation plan and, where relevant, proof of parking provision. We supply all certificates; the building application runs through the AKNW partner. -
05 A retrofitted dormer — effort and permit?
Shed and gabled dormers in NRW require a permit in many cases, depending on size, position and the requirements of the local development plan. We clarify the structural connection to the rafters or purlins, and likewise the building physics (vapour barrier, thermal bridge). Fixed price from €4,165 gross for the structural engineering plus execution planning of the dormer. -
06 What does an extension cost in total — fees plus construction costs?
Our fee corridor runs from €5,355 (a small conservatory, exempt from procedure) to €11,305 (an extension with habitable rooms, a building application, full construction management). Construction costs vary widely: the BKI mean value for a high-quality extension is €2,800–3,600/m² of gross floor area, depending on the existing building and the specification. A first cost estimate comes with the variant study. (BKI = the German building-cost information centre.) -
07 Who takes on construction management for an extension or conversion?
Robin Henn as civil engineer — LP 8 site supervision himself, on site. 10 years in the profession, more than 70 completed building projects. Only the LP 4 building-application submission runs through the AKNW partner architect. The client has a single point of contact from concept to handover of the keys.
Plan the extension. Fix the price. Add construction management.
Send us the year of construction, your extension idea and the plot situation — we will check procedural eligibility and provide a fixed-price proposal within 24 hours.