Dormer, roof extension or extension: which fits your house?

When a family outgrows its house, there are three ways to add space without moving: a dormer in the roof, a roof extension that adds a whole floor, or an extension at the back of the house. They solve different problems, and choosing the wrong one is an expensive mistake. This guide compares the three, based on the houses we work on across Brabant, from Eindhoven and Veldhoven to Den Bosch, Tilburg and Breda.

Start with the question, not the solution

The right choice depends on what the space is for. If you need one more bedroom or a quiet place to work, the attic is usually the answer. If you need two or three rooms upstairs, a dormer will not be enough and a roof extension becomes the realistic option. And if the problem is downstairs, a kitchen that is too small or a living room where the family does not fit, then no amount of attic space solves it and an extension is what you need.

Many families actually have both problems. In that case it is often smarter to do both at once: one scaffold, one planning, one round of disruption.

When a dormer is the right choice

A dormer pushes the roof out on one side of the attic, giving you standing height and a proper window. It works well when your attic already has a usable floor and a fixed staircase, or room for one. A prefab dormer is fitted in a single day; one made to measure takes one to two weeks on the roof. It is by far the cheapest way to add a usable room.

The limit is the width of the roof and the height of the attic. In a small attic, a dormer gives you one room, not two. Details and price ranges are on our dormer window page.

When a roof extension is the right choice

A roof extension adds a complete floor. On a house with a flat roof, a new storey is built on top. On a pitched roof, the roof often comes off and a full floor with a new roof goes on. You gain full height everywhere, and usually room for two bedrooms or a bedroom with its own bathroom.

It is a structural job and always needs a permit. Before anything is designed, a structural engineer checks whether the walls and foundation can carry the extra floor. In many 1960s to 1980s houses in Eindhoven, Veldhoven and Tilburg that is possible, sometimes with reinforcement. More on our roof extension page.

When an extension is the right choice

An extension adds space where most families feel the pinch: the kitchen and living room. The most popular layout moves the kitchen into the extension, with sliding doors to the garden, and turns the old kitchen into living space. The ground floor goes from cramped to open.

Up to 4 metres deep at the back is often permit-free, within limits on height and how much of your garden is built on. On a corner plot or in a protected area the rules are stricter. See our home extension page for types and guide prices.

What the house itself decides

The roof

A steep pitched roof with a good attic floor is ideal for a dormer. A low-pitched or flat roof makes a dormer pointless but makes a roof extension much easier.

The garden

An extension needs garden. If yours is short, or if building on it would leave you with almost no outdoor space, going up is the better choice.

The structure

A roof extension puts weight on the walls and foundation. A dormer and an extension barely do. If the structure cannot take more weight without major reinforcement, that pushes the choice towards a dormer or an extension.

The rules in your street

In many Dutch streets the neighbours already have a dormer or extension. That is useful, because a municipality usually approves what already fits the street. In protected areas such as Philipsdorp in Eindhoven or the centre of Den Bosch, the rules are stricter for anything visible from the street.

Doing two at once

A popular combination is an extension downstairs and a dormer upstairs, done in one project. Another is an extension with a floor on top, which gives you space on both levels in one structure. Combining saves on scaffolding, site setup and planning, and you only live through one period of building work. It does mean a bigger budget at once, so it helps to know the numbers per part.

Summary

One extra room upstairs: a dormer. Several rooms upstairs: a roof extension. More space downstairs: an extension. Your roof, your garden and the structure of your house narrow it down further, and the rules in your street decide how easy the permit will be. We build all three across Brabant and can tell you at a first visit which one fits your house, in English.

Frequently asked questions

Which option adds the most value to a house?

Generally the one that adds the most usable living space: a roof extension or a larger extension. But value also depends on what buyers in your area want. In family neighbourhoods an extra bedroom often adds the most.

Can I stay in the house during the work?

For a dormer and an extension, almost always. For a roof extension usually too, though there are a few noisy days and the moment the new staircase is connected.

Which one needs a permit?

A roof extension always does. A dormer on the back roof and an extension up to 4 metres at the back often do not, as long as they stay within the national limits. We check it for your address.

What if I am not sure the structure can take it?

Then the first step is a structural check. We look at the walls, floors and foundation at the first visit and involve a structural engineer where needed, before anything is designed.

Back to all guides