Dormer window

Your home becomes more attractive with a dormer. But what exactly are the advantages of a dormer window? This article will help you make the right dormer choice. From wood to plastic, with a pitched or flat roof: find all options with corresponding price indications.

What does a dormer cost?

Dormer windows are generally supplied in wood, plastic or polyester. Dormer window costs start at £6,500. For this, you have a plastic dormer 2.5 metres wide. Below are the average prices per material type and size.

The benefits of a dormer window

With a dormer window, you can boost your home’s comfort. If you buy a dormer, these are the main benefits:

• More space: Divide your home more efficiently and enjoy more space and less awkward sloping walls on the upper floors.
• More light: The few small windows often make your attic dark. With a dormer window, you add a healthy dose of daylight to the rooms in question.
• The value of your home goes up: A dormer window is an attractive addition to any home. The extra walking space a dormer provides increases the value of your home.

Do you need a permit to install a dormer?

Not always. If you want to build permit-free, you need to meet a number of conditions:

• Your house must be constantly occupied.
• Your dormer is not on the front or side of your house. The municipality sees anything adjacent to public land as having a major impact on the immediate surroundings. And then a permit is required. When your dormer is at the back of your house, it logically has less impact on the immediate area.
• Your dormer has no pitched roof. Instead, it has a flat roof with opaque sides.
• Adhere to the regulations for the size and placement of the dormer.

Maximum dimensions for a permit-free dormer:

• Height of dormer: maximum 1.75 m
• Bottom: placement between 0.5 m and 1 m above the eaves
• Top: placement at least 0.5 m below the eaves
• Sides: placement at least 0.5 m from the sides of the roof surface
• Sides in case of the terraced house: placement at least 0.5 m from a house separating wall

Permit check

If you do not meet the above conditions, you may need a permit for your dormer. The costs for a building permit are, on average, 2% to 5% of the total costs, with a minimum of £ 150. The exact costs vary per municipality.

Do you doubt whether you need to apply for an environmental permit? Use the Environment Counter’s permit check to check whether you need a permit within minutes.

How to apply for a permit

Is it necessary or even compulsory in your situation to apply for an environmental permit? Then contact your municipality or log in to the Omgevingsloket website. You can log in with your DigiD and see which documents you must submit. Think of building drawings and construction calculations. Another possibility is to contact your dormer specialist and ask him to take care of your application.

After you have applied for your permit, you will hear within 8 weeks whether you have permission to install your dormer. After this, your neighbours can object for another 6 weeks. The municipality then has 6 weeks to respond to this objection. So inform your neighbours in good time. After the objection period, your permit is irrevocable and you can build with peace of mind.

Which dormer window suits your situation?

Get the most out of your dormer window. We would like to give you the information you need to make your choice here. Think about:

1. Traditional versus prefabricated installation
2. Flat versus pitched roof
3. Material choice: plastic, polyester or wood

1. Prefabricated versus traditionally built dormer

These different ways of installation both have their advantages and disadvantages. Do you have the dormer assembled on site? Or do you opt for a prefabricated dormer that is lifted ready-made onto the roof? Find out which one suits your situation here.

Prefab dormer: The components of this prefab dormer are made in the factory and often already assembled in the factory. This allows this type of dormer to be installed in 1 day.

Traditionally built dormer: This type of dormer is built on your roof on-site. This may be preferable, for example, if a crane cannot fit in the street. Traditional installation may also be the best choice if the house is no longer perfectly straight. The pieces can then be accurately placed on the roof.

2. Sloping or flat roof

The roof has a lot of influence on the performance of the dormer. For instance, a dormer with a pitched roof lasts longer. We zoom in briefly on the different features and advantages of both different roofs.

Roof dormer with a sloping roof (trailing roof dormer)

A sloping roof carries several advantages.

• Low maintenance: Because rainwater flows off the roof by itself and this rainwater also carries away debris such as leaves and branches, this type of roof requires less maintenance than a flat-roofed dormer.
• Long lifespan: The lifespan is longer than a flat-roofed dormer. Apart from the roof being less exposed to water and dirt, the roofing lasts longer. Roof tiles, often the best roofing material, last extremely long. Sometimes up to 80 years.
• Smooth transition with the roof of your house: The appearance of your dormer can be a reason to choose a pitched roof.

Flat-roofed dormer

A flat-roofed dormer is popular because it fits almost all types of houses. Most people opt for a flat roof. The advantages are:

• Economical: The price of a flat-roofed dormer is lower. This is because the construction of your roof does not need to be changed as much. This saves a lot of effort and thus costs.
• Easy to install: A flat roof is fairly standard and therefore requires few modifications. This makes it easy to install. With a prefabricated dormer, placement is done within a day.
• Permit-free: To have your dormer built without a permit, you must meet several conditions. One of these conditions is to take a flat-roofed dormer.

3. Wooden, plastic or polyester dormer?

The choice of material largely determines the success of your dormer. We compare the three most common types of material.

The inexpensive choice

If you are looking for an inexpensive dormer window, you will soon end up with plastic. People quickly associate plastic with ”an ugly plastic cheap material”. This is unjustified. Nowadays, plastic is almost as beautiful in appearance as wood and is no more expensive. Plastic has excellent value for money.

A quality choice

A polyester dormer is of very good quality. The material insulates extremely well and is virtually indestructible. Because it is cast in a mould in the factory, the material is also leakproof.

Wondering about the advantages per material type? You’ll find them below.

Advantages of wooden dormers

Wood is a favourite for many people because of its beautiful appearance. Find the advantages of a wooden dormer here:

• A classic and natural look;
• Can be customised and adjusted by your own input;
• Wood is easy to paint and in many colours;
• Eventual damage is easy to touch up;
• Wood is environmentally friendly if it has the FSC quality mark.

Advantages of plastic dormer

A plastic dormer features a basic wooden construction with plastic as a finish. The advantages:

• Plastic is an economical choice. The purchase price is not high and maintenance costs are very low;
• This material is waterproof and resistant to extreme weather conditions;
• Fire-resistant. Plastic is suitable for many situations where fire resistance requirements are imposed;
• Isoles very well. Heat loss is minimal.

Advantages of polyester dormer

Polyester is also plastic. Yet there is a big difference in it. A polyester dormer is padded with insulation foam instead of the basic wooden construction. This makes this type of dormer seamless and only available as a prefab (ready-made) variant. The advantages of polyester are:

• Very durable material. It sometimes lasts up to 80 years;
• Resistant to extreme weather conditions;
• Keeps maintenance to a minimum;
• Fire-resistant;
• Insulates excellently;
• Low roof load as polyester is lightweight.

Restore your old dormer.

Instead of buying a new dormer, you can also choose to have old parts refurbished. If only one or a few parts need replacing, a dormer renovation is attractive, even financially. For the average cost of a renovation, take a look below. £100 per m2

Replacing lead flashings
£ 650

Take advantage of the experience of a specialist and ask them for advice when in doubt. Is renovation wise in your situation? Renovating normally consists of one or more of the following work:

• Replace your window frames
• Install insulating glass
• Replace side cheeks and fascias
• Replace roofing
• Insulate the roof and side cheeks
• Finishing the dormer with lead flashings

Go for quality with dormer quality marks

We recommend that you look into quality marks around dormers and specialists. We have listed a number of important quality marks for you, both for the dormer specialist and for the material.

• KOMO: KOMO guarantees the quality of products and services in the Dutch construction industry. By hiring a dormer specialist with the KOMO quality mark, you can be sure that the quality is reliable and good.
• FSC: Wood with the FSC label has been an environmentally friendly choice. FSC indicates that this material is sustainable and comes from responsible forests

Tips when buying a dormer window

The future success of your dormer window owes a lot to the experience of the professional. We offer some tips.

Choose a local company.

Seek out a dormer window specialist in your area. By doing so, you will save on call-out charges, which increase from the moment the specialist leaves his place of residence. Moreover, a specialist who is close by is particularly flexible.

Check reviews

Do you want to be sure you are hiring a good specialist? Reviews will often help you a long way. This can be in the form of word-of-mouth but also by searching online. For example, research what previous customers have said about keeping appointments, the quality delivered and overall experience with the specific company.

Quantum discount

Do your neighbours also need more attic space? Then discuss with them whether the project could possibly be carried out at the same time. This could take the form of a double dormer across both roofs or two separate dormers being installed at the same time. If a specialist can carry out several projects at the same time, this could save you in overall costs.