What is a second-storey extension?
A new floor is built on top of the existing structure or roof, creating substantial extra living space within the same footprint.
Second-storey extension
Second-storey extension made to fit.
A second-storey extension adds a full extra floor to your house. It is ideal when garden space is limited or you need bedrooms, a bathroom or workspace upstairs.
BouwGarant · 10-year structural warranty · Response within 24 hours
Benefits
Keep your garden
Gain a full floor without giving up outdoor space.
Extra rooms upstairs
Perfect for a growing family, a bathroom or a quiet office.
Structurally checked
We assess foundations, walls and load paths before committing to the design.
- BouwGarant certified
- 10-year structural warranty
- Fixed price upfront
- Response within 24 hours
About second-storey extension
Everything you need to know.
Costs
In 2026, second-storey extensions usually range from EUR 1,200 to EUR 3,200 per m2 depending on structure, finish and permit requirements.
Permit and engineering
A second-storey extension almost always needs a permit and structural calculations. We coordinate the full process.
Recent second-storey project
Modern second-storey extension on a terraced house
See how this terraced home gained extra upstairs rooms, with a calm street presence, a careful connection to the existing structure and the garden left intact.
View project case ->Cost estimate
Calculate your second-storey extension.
Process
From first idea to handover in five steps.
- 01
Request & advice
Tell us about your plans online or by phone. We call back within 24 hours with first advice.
- 02
Site visit & design
A specialist visits, measures the space and discusses materials, layout and feasibility.
- 03
Fixed-price quote
You receive a detailed quote with a clear fixed price and scope.
- 04
Permit & planning
When needed, we coordinate the permit process and agree a practical construction schedule.
- 05
Build & handover
Our own craftspeople build the extension and walk through the result with you at handover.
Client stories
What clients tell us.
Read how homeowners throughout the Netherlands expanded their homes with an extension, second storey or conservatory.
We twijfelden lang of een aanbouw op ons rijtjeshuis wel haalbaar was. Na het adviesgesprek bleek het gewoon te kunnen. De doorbraak naar de woonkamer was spannend, maar binnen twee dagen dicht. In totaal 9 weken van start tot oplevering, precies zoals afgesproken.
Familie De Vries
Haarlem · Aanbouw 18 m²
De stalen pui was voor ons doorslaggevend. Aanbouw 24/7 heeft het hele traject begeleid, inclusief vergunning en constructieberekening. De planning schoof één week op door het weer, maar daar werden we op tijd over geïnformeerd. Eindelijk een woonkamer met licht.
Sophie van Dijk
Utrecht · Uitbouw woonkamer 24 m²
Aanbouw van 16 m² voor een open keuken met schuifpui naar de tuin. We hebben zelf de vloer en het schilderwerk gedaan, dat scheelde behoorlijk. De ruwbouw stond er in 5 weken. Communicatie via een vast aanspreekpunt, dat werkte heel prettig.
Lisa Bosman
Amersfoort · Keuken-aanbouw 16 m²
Frequently asked questions