Going up in the World - 2
Ivy Ngeow RIBA
October 2003
Copyright reserved, see legal statement

In the last issue, we discussed the possibilities of converting your existing roof space into a new usable room. We discussed planning permission, employing an architect and approximate costs. In order to submit your application, there are three basic roof forms which your new space will take:

1. Existing roof pitch retained: This is the cheapest of the three options because it facilitates the use of the floor space and roof area by inserting rooflights like Velux windows and a new staircase. However, you can only opt for this form if you have a steep pitch to begin with, for example 40 deg and steeper.
2. Existing roof pitch retained with new dormer windows: This is the second cheapest option. Dormer windows are those wedged-shaped windows with a roof and sides fitted into an existing pitched roof. By creating full head height areas in a pitched roof construction, it is a good option for those who cannot have the first option. Dormer windows help increase the usable floor area. Many houses in conservation areas are required to have dormer windows when converting their lofts.
3. Existing roof pitch retained on front pitch with mansard roof on back: This is the most expensive option, but it creates the most usable space, because it maximises head height on the entire back half of the house. The back pitch of the existing roof is removed, a new flat roof and mansard back pitch is added, into which windows are fitted. The mansard is often 70 degrees in pitch in some councils, depending on the existing streetscape. In all the three roof forms, a front escape window of a minimum size of 450mm x 450mm is necessary for escape during a fire. This window size should generally be a tenth of the floor area as a guide.

Staircases most commonly continue over the existing stair direction. Staircases in the first and second roof forms have to 'wind' more. This means that a straight flight is out of the question. This is because as you are ascending, the roof pitch is getting closer because the roof is sloping down towards the back of the house. Therefore the disadvantage of retaining your roof pitch is that the staircases eat in more into the usable floor area of your new room. The minimum head clearance is 2m in domestic applications in order to building regulation requirements. Some people have used spiral stairs, but it is much more impractical when moving large items of furniture (eg mattresses) up and down. In the mansard option, a straight flight is possible, if the mansard is almost vertical, i.e 80 or 90 deg.

When you increase your accommodation, it is normal that the loading on your existing services would increase. Your new services such as plumbing and electrics should be connected to the existing supply, therefore you may need to increase the capacity on your mains. If you choose to have a new bathroom in your loft room, it can increase the price by five to ten thousand pounds depending on the size, design and the specifications of your bathroom. If you have not budgeted for this aspect of the construction, it is best not to embark on it unless you do not mind the cost implications. Bathrooms should always be thought of at the beginning of the design process, not at the end. This is because altering and adding to existing plumbing, sanitary fittings, and tiling are very expensive if they are of any quality. Also, another reason why you should design the bathroom into the scheme at the earliest stage is the issue of head height. The shower and handbasin, for instance, can only be where there is full head height, whereas the WC can be at points where there is lower head height, if needs be.

The first issue about plumbing costs is that if the new WC cannot be located near an existing soil vent pipe, you may have to install a macerator. This is an electrically powered waste disposal machine, chopping up and pumping waste through a smaller pipe to the nearest soil pipe. They are not that noisy these days but still you should install them only when the normal soil pipe is not possible. Your architect, builder or plumber will be able to advise you.

The second point to mention about plumbing is that shower fittings are expensive. Make sure that another shower or bath being run elsewhere in your property will not affect the water pressure. There are numerous ways of ensuring that the high pressure is retained for modern showers, for instance, pumps or a higher capacity tank. Again, seek advice from the professionals. There is no point in installing a new shower that has poor pressure because it is a complete waste of money.