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There are many styles and types of dormer windows that can be used in loft conversions. We have summarised this, and added a few pointers of our own, on where we think it's best to position them.

ABM are able to advise you on how best to convert your loft space, and then set about transforming that unused space to what ever you require, be it a master bedroom including an en-suite shower room or two additional bedrooms, the options are endless.

Our experience has shown us that our customers are never seldom short of ideas, our strength is the realisation of these ideas and our ability to design your project firstly to meet your requirements and secondly to provide a design that enhances your home.

The design, position and size of a dormer really depends on two factors:

1. Which elevation the dormer is to be positioned on - Front, Side or Rear.
2. What you are aspiring to achieve by introducing a dormer. Do you require more floor area or head room, or is it simply that you don't like roof lights and you need to allow the natural transmission of light.

A box type dormer offers by far more useable floor area and head height than any other type. A hipped or gable style dormer affects the useable floor area & head height, and the width of a gable or hipped dormer also affects the pitch and height of the roof ridge. This is normally dictated by the existing ridge line - remember the wider the dormer, the higher the ridge. Dormers can be all different shapes and sizes, below are just a few examples (click to enlarge).

If you plan to add a dormer to the front elevation, you need to firstly take a look at the other houses nearby, and the street scene, and consider if introducing a dormer would make your property look out of place. If you live in a detached house or there's no apparent relationship with other dwellings you would have a greater chance to achieve planning permission. Your planning department will resist any major alteration other than allowing for natural light, or to allow the introduction of the stairs to your loft conversion, however if you are lucky enough not to have to apply for planning permission (your alteration falls within permitted development) you can add what you wish depending on the volume and a couple of other important factors, which are laid out in the new guidelines. Remember the volume is only the external area of the dormer.

ABM would normally design dormers to the front elevation that relate to the style and proportion of the windows below and try to position them so as to respect the symmetry of the existing building. We think they should be regularly spaced, though not necessarily immediately above the windows below. However dormers positioned at the edge of the roof will look visually weak and produce an unbalanced elevation. Dormer windows should also be set back from the building line and below the ridge line of the existing roof. They should be visually subordinate to the roof slope. Whenever possible and instructed to do so we will use reclaimed materials which allow the dormer to blend in more naturally with the existing roof scene.

Rear elevation dormers.
A very important factor is whether your dormer and loft conversion needs planning permission. If it does not then it really is down to you what size and type of dormer you require (depending on information previously stated). You firstly need to consider what you are trying to achieve by converting your loft. You might want to add a additional bedroom or bedrooms, en-suite bathrooms including a walk-in wardrobe. Remember, the bigger the dormer the more usable floor area you will have to convert. Below are a few examples:

Fig 1: Typical box type roof dormer.

This type enables you to gain by far the most space and floor area. It is normally built to just within the full width of your roof plane, and again must be set back from the outside wall and down from the ridge line (click to enlarge).

Fig 2: Smaller Hipped or gable dormers.

This style of dormer is more attractive if built correctly, using the right materials (reclaimed if possible), not having the dormers too large and positioned as previously mentioned. It tends to blend in much better with the roof scene, but this style does reduce the usable floor space. The width of this style is dictated by the existing ridge height. The wider the dormer the higher the ridge (click to enlarge).

Fig 3: Arched / eyebrow dormers and cats slide.

This style of dormer relates to the hipped dormer (fig 2). By incorporating an arch or curve it allows the appearance to blend in more naturally roof scene, but again it reduces the head height and usable floor area (click to enlarge).

Fig 4: Large Gable or barn hip.

Usually a large gable style dormer is added to the side elevation to achieve maximum floor area and head height required for the stairs. A normal combination would be a side elevation gable or barn hip and a full rear elevation box style dormer. In some instances you would have to consider building a dormer to the side elevation to allow for the head height required for your stairs (part K of the current building regulations) to provide access to the loft (click to enlarge).

ABM are specialists in loft conversions and installing dormer windows and rooflights in all areas including Horsham, Crawley, Billingshurst, Dorking, Epsom, Faygate, Kingswood, Reigate, Rusper, Surrey and West Sussex. We are able to offer you free advice on loft conversion dormers, attic conversions and the many different styles of dormers that would suit your home.