When do you need a roof-addition drawing?
A roof addition is the most far-reaching way to add extra living space to an existing home without expanding into the garden. By placing a complete new storey on the roof, space is created for a master bedroom, extra bedrooms or a hobby space. Because the building height and silhouette of the home change, a roof addition is almost always subject to a permit and the municipality requires a complete, scale-accurate construction drawing.
Typical scenarios where a roof-addition drawing is needed:
- A flat-roof terraced house where an entire extra floor is added.
- A home where the existing attic is replaced by a full storey.
- Expansion for a growing family without moving or giving up a garden.
- Matching a neighbouring property that already has a roof addition, to continue the streetscape.
What does a roof-addition construction drawing include?
A roof-addition drawing shows in detail how the new storey connects to the existing home. The floor plan of the new storey shows the layout, room dimensions, stair connection and any roof windows or dormers on the new layer. Facade views are drawn from all relevant sides, because a roof addition is clearly visible from the street and the aesthetic committee assesses the design thoroughly.
Cross-sections show the height of the new storey, the connection to the existing truss structure and the new roof shape. A site plan shows how the home stands in the street after the roof addition relative to the neighbours. For terraced houses, a view of the entire building block is often included to support the integration.
Permit, aesthetic requirements and zoning plan
A roof addition is subject to a permit in almost all cases, because the building height and silhouette of the home change. Only in very limited cases at the rear of a home, within strict conditions of the Buildings (Living Environment) Decree, can a roof addition be permit-free. For the municipality, the zoning plan plays an important role: it determines the maximum permitted building height and eaves height of your home.
For a roof addition, aesthetic requirements weigh heavily. Many municipalities have specific policy rules for roof additions in a street or neighbourhood, to prevent the streetscape from becoming incoherent. Sometimes a roof addition is only approved if the neighbours already have a roof addition or if the design matches a previously approved reference example in the street.
What does a roof-addition construction drawing cost?
A roof-addition construction drawing is available from €400 including VAT. The final price depends on the complexity of the design, the availability of existing construction drawings and whether there is a special roof shape. A roof addition on a flat-roof terraced house can be drawn faster than on a home with a pitched roof where the existing truss structure has to be entirely replaced.
In addition to the drawing, keep in mind the structural calculation, because an extra storey considerably increases the load on the foundation and load-bearing walls. The municipal permit fees also rise for larger interventions, because the fees are a percentage of the construction cost.
Difference with a dormer and a ridge raise
The main distinction: with a roof addition, a complete new storey is placed on the roof. With a ridge raise, only the existing ridge is raised to gain standing height, without a full storey being added. A dormer is a protrusion in the roof surface, with which you locally create standing height and daylight without the total height of the home changing.
The choice between a roof addition, ridge raise and dormer depends on how much space you gain, the budget and the aesthetic rules in your street. During the intake, we look at which option suits your home and what is realistically achievable in your municipality.
