Overview and Tools
Lead
is the ideal material to use for flashings and weatherings. It is extremely
malleable and can easily be bent and dresses to fit the various types of
contoured roofing tiles used in both old and modern buildings.
When
fitted correctly, lead sheet is a very long-life material which makes it ideally
suited for flashings over other long life materials such as tiles, slates, EPDM
synthetic rubber, and many other types of materials used around the home like
hardwoods and uPVC.
This
guide covers the following:
Ø
Clips and Clipping
Ø
Cover Flashings
Ø
Soakers and Step
flashings
Ø
Pitched Valley Gutters
Ø
Ridges and Hips
Ø
Flashings to windows
Ø
Small Extensions and
conservatories
Ø
Porches and Bay Window
Tops
The tools required for fitting lead sheet are a dresser, bossing stick, straight snips, hammer, plugging chisel, straight rule, lead welding equipment or soldering iron.
Lead
sheet for flashings is most commonly sold in 6m rolls
(4 x 1.5m lengths) in widths from 150mm to 600mm in increments of 30mm.
Code
numbers relate to the thickness
-the higher the Code number the thicker the lead – see table A on the window flashings page.
Before
commencing any lead-work it is important to remember the following basic rules:
Individual pieces of lead sheet must not exceed the recommendations of the lead sheet Association. In particular each piece of flashing in code 4 must be no longer than 1.5m.
In
exposed positions the use of code 5 will provide a greater resistance to wind
lift, although the use of adequate edge clips is of paramount importance. This
is particularly relevant when fixing ridges and hips as detailed later.
Fixings
must hold the lead securely in position without restricting thermal movement.
With flashings, regular expansion joints (laps) will overcome the restriction
caused by lead wedging along one side.
Nail
and screws should have a similar life expectancy to that of the lead, therefore
use copper, brass or stainless steel – never
galvanised
or aluminium fixings. Joints must allow for thermal movement but also remain
weathertight for the positions where they are used.
Other
materials Required Patination Oil
On
completion of all leadwork an application of patination oil is required.
Where
lead is turned into brick-work or masonry a sealant is required for pointing.
Where
clips are required, fixing details are shown later.
Patination
Oil should be applied to all leadwork. It can prevent unsightly white staining
on materials fixed below the lead and provides a pleasing surface appearance.
It
is important to:
Shake the can vigorously before use. Apply the oil with a soft cloth as soon as is practical after fixing, but never later than at the end of the day’s work. Lift flashings and coat the under-side of the lead for about 50mm from the edge.
This
can prevent white ‘dribble’ when rainwater penetrates up under the flashing
in storm conditions.
Coat
the lead before turning up clips around the edges.
Remember
to coat between laps.
Don’t
use linseed oil as an alternative to patination oil.
If lead is to be fixed by nailing it is important to use the correct nails. Nails and screws should have a similar life expectancy to that of the lead, therefore use copper, brass or stainless steel – NEVER galvanised or aluminium fixings.
Why
is that so many water penetration problems occur at abutments?
The
answer often is that mortar is not a satisfactory long-term pointing where lead
flashings turn into joints in brickwork or masonry.
The
mortar is unable to adhere to both the brick and the lead when subject to
changes in temperature. It soon cracks, particularly in sunny exposures,
allowing water to penetrate, causing dampness below. In many cases the problem
is made worse by poor cleaning out of the joint which results in a wedge-shaped
pointing which quickly cracks away from the brickwork.
Now
there is a practical alternative to mortar pointing – Lead Sheet Sealent. This one part, neutral cure, high-performance silicon-based sealant has
been specially formulated for use with lead sheet flashings and its elastic
properties make it ideally suited for pointing between lead and brickwork or
masonry.
The
sealant is specifically designed for pointing joints between lead and brickwork
or masonry.
Colour
matched to lead.
Provides a long-term, flexible
joint,
which can absorb temperature changes.
Avoids
the problems of pointing with wet mortar, particularly in hot or frosty
conditions.
Quicker,
cleaner and easier to use than mortar.
The
Lead Sheet Association recommends sealant.
HEALTH
& SAFETY FOR LEAD