Attic Extensions are usually the most cost efficient way of adding value and space to your home, with it adding a third to the total space in the average house. When done professionally it adds a lot to your home, when done wrong it can be your worst nightmare. Below our some of the basics to help you gauge what the best course of action would be for you.

What height is needed?

Fairly obviously, the height must be at-least the height of the average person. less obvious is taking into account loosing 6 or 7 inches to account for the new flooring and supports. If this is a struggle, it is possible to lower the floor by lowering the ceiling of the rooms below or by constructing a new roof.

Are the internal walls taking any of the load?

It is very important at the design stage to figure out how this is going to be evenly distributed throughout the house.

If the house has a traditional timber roof (usually pre 1950) there’s a high chance that one or more internal walls are taking some of the load from the roof. However, if it is a new house the chances are that the internal walls are not taking some of he load.

Our experience in all kinds of conversions allows us to design most of them so that extra loadings do not need support from any internal walls.

However, if available and capable of taking the load, using the internal walls can save money as the design can be kept as simple as possible.

For internal walls to be used for support, they must be able to take the load from the roof. Signs that the walls are likely to meet this conditions include:

  • Blockwork walls
  • Solid, double brick or more walls
  • Walls unlikely to be of use are:
  • Hollow partition brick walls
  • Plasterboard partition walls
  • Timber walls

However there are some exceptions, Victorian era and before timber walls can sometimes be structural.

Where will the new stairs go?

Fitting in stairs can be more trouble than first imagined. Especially if it is a small house, unless it is a traditional Victorian era or semi-detached home.

In these houses, stairs can usually be fitted directly above or ran parallel to the existing ones to minimise the loss of space. As with most semi-detached houses the roof will be hipped meaning there will be no room to climb the stairs when at the top.

A simple solution is to build a large side dormer or doing a hip-to-gable conversion. However, if this is not a wanted solution, it is likely that the stairs could in theory be placed anywhere below.

If there isn’t enough space to fit normal stairs, it may be possible to fit a compact staircase. However they are not particularly popular with Building Control and so would have to be used as a last resort.

Is there an entrance hall?

Fire regulation is very important to follow with any type of extension or conversion. The layout of the ground floor and the position of the main hall door can have a major impact on the cost of getting a new design to comply with the fire regulations.

An ideal ground floor layout would have an entrance hall leading in from the front door to the main stairs. If the house doesn’t have this layout then it will have to be redesigned before we can start work.

It is also important to consider any extra internal walls being built during the construction process. These walls will act as the main defence if a fire were to occur.

Are there tanks and pipes that need to be relocated?

It is common for a large cold-water tank to be placed in the middle. It is important to remember that everything in your attic is going to have to be relocated, at least for the duration of the construction.

Things such as boilers and tanks  present a more problematic situation. These cannot simply be moved as that would cut off the heating around your home.

Tanks and pipe work can usually be successfully relocated to the corners, out of sight in a cupboard, or some similar accommodation.

If the tank is out-dated it may be easier to replace the tank with an unvented hot-water system such as a Megaflo pressurised system or combination boiler which do not require the large cumbersome tanks.

Is the roof in a suitable condition?

Before starting the construction it may be a good idea for us to survey the condition of the roof as construction cannot start until the roof is repaired.

Things to check:

  • Missing Tiles
  • Leaks
  • Damp
  • Capping of chimneys
  • Infestations


On an aesthetic level it would be unwise to place a roof window where a chimney stack eliminates the view. But more important is if the chimney has been properly supported.

Adding a large new dormer or other extension may interfere with the airflow for the chimney. Chimney stacks must rise 900mm above the ridge height so expanding the attic may need an increase in the height of the chimney stack. This is likely if the roof is hipped and a hip-to-gable conversion is a likely option.

Party walls

Most conversions utilise some steel beams that are embedded into old party walls which naturally increase the loadings to the rest of the house. That is why it is important to have your party walls in tip top condition.

Party walls are normally the length of a single brick thick (approx. 225-230mm) but this is not always the case.

On older properties the length may only be half a brick thick due to builders saving money by laying bricks sideways. This is a serious flaw and must be attended to before building can commence.

This may seem bad, but things can be worse. In some traditional Victorian terraces walls may be omitted completely! New party walls are often built from concrete block work and are sometimes only 115mm thick. If your party walls are omitted or undersized they will need to be rebuilt.

If the house has chimney breasts in the roof these must also be considered before embedding the large steel beams as it is not permissible for the structural beams to be fitted directly into the chimney breast.

If the neighbour’s attic has been converted/extended before, then the chances are they have steel beams in their party walls as well. The beams need at least 100mm either end for support so it’s important to find out the position of your neighbour’s beams before advancing.

Main walls

Properties before the 1930’s often have solid brick walls about 230mm thick or even solid stonework which can be more than 400mm thick. Houses built after the 1930’s often have cavity walls which are between 260mm and 300mm thick, whereas modern cavity walls incorporate a timber frame inner leaf.

Older buildings are more prone to defects which means there can be potential problems before the conversion. All walls must be checked for cracks and other defects before continuing. Any cracks must be followed up before additional loads can be applied.

Newer buildings are also at risk…

The lightweight concrete blocks of the inner leaves have a maximum load bearing weight and so all of this must be considered before starting a conversion.

Roof replacements

If after the survey, we decide that it is not advisable to have a conversion/extension with the current roof there are other constructions that can be considered.

Sometimes it can be more beneficial to rebuild the roof from scratch. If the current roof is too shallow to provide sufficient headroom then this may be the only option.

A downside of roof replacement is the need for planning permission.

Although it may seem like a huge and costly job, it isn’t as dramatic or expensive as it may seem.

It won’t cost any more than the equivalent sized home extension.

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