Civil Engineering Reference
In-Depth Information
standard of resistance to leakage
without making it difficult to open, or
without providing extra protection
such as a canopy or even a porch (see
BS DD171
(196)
). Outward opening
doors are much easier to make
weatherproof, but even these may
need the extra protection of a porch in
the most exposed situations (Figure
5.8).
Inward opening doors may lack
weatherbars or weatherboards,
weatherbars may be incorrectly
positioned (Figure 5.9 on page 198)
and door frames may lack adequate,
correctly positioned drainage
channels. Sills and sub-sills may lack
drips or throating on the undersides of
projections. If doors are not
weathertight, surrounding materials
and finishes may have become damp
and deteriorated. Diagnosis of a
weathertightness problem is often
complicated by condensation. There
are some simple principles that can be
employed to improve weather
resistance
(197)
:
●
track across their stop ends (Figure
5.10 on page 198)
Thermal properties
The average thermal insulation
value (U value) of a typical single
glazed wood framed door will be
around 5.0 W/m
2
K, depending on
frame materials and air gap sizes. A
solid unglazed timber door should
give around 3.0 W/m
2
K and half
glazed doors will give somewhere in
between these figures.
External doors should be checked for
warping and twisting which can give
rise to poor airtightness or inadequate
wind resistance.
Case study
Leaking hardwood doors
The BRE Advisory Service was asked to
carry out an assessment of external door
weathertightness problems in a house.
Leakage of doors had been complained of
by the owners of this property since
completion. Despite extensive remedial
measures involving additional sealing and
weatherings, little improvement had
apparently been achieved.
External doors had been supplied in
American white oak, and were a mixture of
inward and outward opening, both single and
double leaf types, without weatherstripping,
raincheck grooves in frames or
weatherboards at the foot.
Doors and windows had been taped by
the building owners to limit leakage.
Removal of some of these tapes from fixed
light framing revealed poor bedding of
external beads and units, gaps in glazing
compound and gaps at the joints in the sill.
A crack in one timber door stile was
reported to leak.
Doors had an excessively wide gap at the
top, up to 9 mm, tapering to 3 mm at the
base. A single door was seen with additional
rubber seals fitted behind the line of the sill
waterbar. Although not water tested at the
time of the visit, this feature would allow
easy leakage of water draining down to the
bottom corners.
Was the American white oak used for the
joinery a suitable material? BS 1186
(198)
indicates that American white oak can be
used for exterior joinery without
preservative treatment. It should not be
confused with American red oak, which is
not durable and therefore unsuitable.
The simple principles of designing
weatherproof doors did not seem to have
been taken into account by the architect or
makers of the doors. Nor did the installation
take into account established principles of
design to minimise rain penetration on an
exposed, open country site. Remedial
measures involved replacement with
proven designs incorporating weather
resistant features.
rain check grooves at least 6 mm
deep
water bars fitted inboard of the rain
check grooves or rebate. This
requires the door to be rebated too
●
trough sills with adequate drainage
holes and that do not allow water to
●
Figure 5.8
Stable-type door opening outwards,
Saxtead Windmill, Suffolk
Figure 5.7
Not up to standard: a thin annealed glass in a door and low level glazing found on a BRE site
investigation
