In this second part covering the things you should take into consideration prior to doing a loft conversion, we will be discussing a couple of crucial areas like the best way of obtaining natural light, windows, stairs for accessing your new loft space, and your roof’s structure.
Making alternations to the structure of your roof
A majority of roofs are constructed using internal support struts within the loft, propping up horizontal roof beams (purlins) and rafters in pitched and traditional cut roofs, and making a web of braces within modern trussed rafter roofs. These all need to be removed in order to provide space for the new room. New supports need to replace them that won’t impose on the newly created space.
There are numerous ways to alter the structure of a roof for a loft conversion. However, there is one common element to all of them – the ceiling joists most likely will be inadequate for being floor joists. What that means is that new floor joist will need to befitted beside them, raised slight over the ceiling plasterboard in order to avoid any contact with them. The joists (frequently 225mm or 200mm in depth) rise over the currently ceiling joists and form the structure of the floor. Depending on what their span is, they will either bear directly onto newly installed beams or to existing wall plates of internal and external load-bearing walls.
In smaller lofts, frequently floor joints themselves are used for supporting sloping rafters. It is made possible through constructing a 1m to 1.5m high dwarf timber stub wall between the two called an ashlering. Once the supporting ashlering are in place, the internal braces and struts can be removed safely.
Stairs are inevitably hard to design, since space for them tends to be tight. It is acceptable to have narrow winding flights, however they might prove to be impractical, since it is hard getting furniture up them. There are also purpose-built staircases that are available, but they cost around 10 times that of off-the-shelf standard designs, so when planning a loft conversion, keep this in mind.
If it is necessary for you to have a purpose-built staircase, having the Building Control officer approve your design prior to having it commissioned is a good idea. Ask your builder or joiner to send a copy of your design to Building Control. As part of your loft’s fire safety upgrade, your stairway should lead into an external door and hall. If your arrangement is an open plan with the stairs rising from a room, you likely will need to alter this, and fit your choice of escape routes or new partition wall.
Gaining Natural Light and Fitting Windows
Not many structural alterations are needed for accommodating skylight windows. This makes it fairly easy to fit them. Usually the rafters on both sides of your skylights will be trimmed over the top of the opening and doubled-up. On the other hand, dormer windows are themselves structures, since they have a roof and walls in addition to the actual window. At the back of many houses they may fall into a permitted development quota, so planning permission might be required. However, in front of the home, Dormer windows still will require you to obtain planning permission. That is why you often instead see skylights.
Dormer windows might be essential for maximizing headroom inside the loft and for offering useable space. However, support will be needed at the ridge (apex point). A ridge beam gets installed under the apex prior to the roof being weather and the dormer roof joists being put into place. At this point, as the dormer winders are being built, your loft conversion is going to be exposed to the elements. Therefore, good temporary sheeting will be needed in order to provide protection against the weather.