On this page
What is made in advance?
This depends on the selected system. Walls, roof sections and frames can be preassembled to different degrees. Specify which elements arrive factory-made and which junctions and finishes will be completed on site.
When is prefabrication suitable?
An existing building that can be measured accurately and sufficient lifting space help. Limited access or complex connections may affect the choice. During the survey, we assess the transport route and possible crane position.
Structure and waterproofing
Even lightweight construction must suit the existing supporting structure. Roof edges, rainwater drainage and the connection to the old house must also be designed in advance.
What should you compare?
Compare complete specifications: production, transport, crane, assembly, temporary protection, insulation, stairs, services and finishes. A prefabricated shell and a complete roof extension are different quotations.
Installing the shell is only part of the programme
Prefabricated elements are manufactured in advance. Site survey, design, structural preparation, production and scheduling come before installation. Connections, building services and internal finishing may follow. Ask for the complete programme and handover standard. A short lifting or assembly stage does not mean the entire new floor will be ready that day.
Which decisions must be final before production?
Agree dimensions, window positions, roof shape, facade finishes and connections to the existing home. Also discuss the stair opening, service provisions and the division between factory and site work. Changes after production can require additional work and expense. Ask when decisions become final and how revisions are recorded.
From preparation to handover
Space requirements
Decide which new rooms and usable floor area you need.
Site survey
Assess the existing roof, load paths and access.
Design
Develop the height, façades, daylight provision and stairs.
Structural design
Have the additional loads and their transfer through the building calculated.
Permits
Have the design and local rules assessed.
Quote
Itemise the shell structure, installations, finishing and lifting work.
Construction planning
Plan the lifting position, suitable weather conditions and temporary protection.
Opening the roof
Open the roof in a controlled way and protect the home.
Installing the structure
Build the walls and roof in accordance with the structural design.
Weatherproofing
Complete the windows, doors, roof covering and connection details.
Interior work
Install the stairs, services, insulation and interior finishes.
Handover
Inspect the connections and finishes together.
Frequently asked questions
Is the price on this page a quote?
No. An estimate or worked example is for initial planning. The property, materials and agreed scope determine your quote.
What should I include in a quote request?
Describe the work and include the town, postcode, photographs, dimensions and any available drawings. Add your preferred start period. Larger projects need a site visit to establish the scope and price.
Do I need a permit?
This depends on the work, the address and local rules. Check your plan through the Dutch Omgevingsloket and have structural alterations assessed in advance. Work that does not need a permit must still comply with applicable building rules.