Civil Engineering Reference
In-Depth Information
number of proprietary manufacturers of roof window available to suit most pitches from
virtually a flat roof to the side of a mansard roof which would frequently be 60 degrees
pitch or more. These windows can be provided with sophisticated opening systems giving
trickle ventilation, double glazing and incorporate various types of sun blind equipment.
Designs are available from simple small windows for bathrooms and toilets to combina-
tion sloping and vertical windows which offer the ability to allow considerable amounts of
light and ventilation into the loft.
Some typical installations are indicated in illustration 8.14. The left hand sketch indicates
roof windows fitted between trussed rafters, thus avoiding any structural disturbance to
the roof itself and offering probably the most convenient and cost effective way of intro-
ducing an opening roof window into the roof space. The centre sketch illustrates a typical
installation involving trimming an opening which has been described elsewhere in this
topic, thus allowing a larger roof window to be installed. The right hand illustration shows
a horizontally split window running from near ceiling height to the floor level of the loft,
and this type of roof window is available either with an opening upper and fixed lower
section or as a roof 'balcony', in which the lower section pushes out to a vertical position
and with the upper section opening upwards from its top hinges allowing the occupant to
effectively walk out into the open air, with protective guard rails automatically locating
themselves for safety reasons.
Can We Stand Up?
Until the introduction of the Building Regulations 1985, there had been a minimum height
requirement for rooms in roof spaces, but these no longer exist. Depending on the inten-
ded use of the attic, it is desirable to have the maximum area of full height attic possible
even if it is only just over 2 metres high. Clearly the pitch and span of the roof will affect
the usable room within the attic; a narrow but steep pitch roof may be as useful as an attic
conversion as a larger span, shallow pitch roof. In this respect many houses of the 1950s,
1960s and 1970s will not prove very easily converted because of the trend in that period to
lower pitch roofs. There is also regional variation in pitch preference, but in recent years
the trend has generally been for steeper pitches. As can be seen in Fig. 8.15, the low pitch
roof is one of the reasons we often see large, somewhat ugly, dormers with their trouble-
some flat roofs extending almost to the ridge just to afford adequate internal headroom
within the attic conversion.
Valley
