T-Pren joints can be placed at a maximum distance apart of 6 metres. Where movement is restricted by an outlet or corner for example, an expansion joint should also be sited within 1 metre of that restriction.
However, The joint spacing depends on the metal and the
gauge used. For most metals, sheets up to 6 metres can be
used by correct choice of gauge, although shorter lengths
might be used for ease of handling or where thinner gauges
are preferred. However for lead, the Lead Sheet Association
recommend a distance of 2 metres for Code 5 lead increasing
to 3 metres for Code 8.
A length of T-Pren is first cut from the coil to go round the
girth of the gutter. This is jointed to the metal sheets, the
length of which gives the correct joint spacing as mentioned
above. The metal sides of the T-Pren should overlap the metal
sheets by a minimum of 25mm and the joint should be made
at least 75mm from the neoprene, or 100mm for aluminium
and copper due to their better conductivity. The neoprene and
its joint with the metal are resistant to heat but it is wise to
place a cold metal surface underneath, as the joint is being
made, to conduct away the heat. Caution is required when
brazing or welding and it may be necessary to cover the
neoprene with a damp cloth to prevent damage from
conducted heat. Naked flames should be kept away from the
neoprene at all times.
The jointing process depends on the metal. TIG welding is
best for aluminium and stainless steel, but low currents must
be used on these light gauge metals. Copper joints can be
soldered but brazing will make a stronger joint. Terne coated
stainless and zinc are best soldered, and where additional
strength is required the overlap can be rivetted before
soldering. For lead, the traditional lead sheet welding
technique for a flat lapped seam is used. A single loading
should be sufficient for Code 5 lead, but where the T-Pren
joint is on top of a lead sheet of Code 6 or higher, two
loadings may be beneficial. Jointing is easiest on flat sheets
but in certain situations the metal sheets and T-Pren joints
have to be pre-formed to shape before jointing. The jointing
will then require extra care, particularly on the vertical sides.
The gutter lining with the T-Pren expansion joints is then
formed to take up the shape of the gutter, placed into position,
and cover flashings formed over the sides. Where heavy foot
traffic is expected in the gutter or where the T-Pren joint is
visible,T-Pren Plus can be used or a cover piece of the
matching metal is clipped over the neoprene section, making
sure that it does not restrict the movement of the joint.
The T-Pren joints should be regularly checked for damage
from foot traffic etc., and where this has occurred another TPren
section should be fixed over the top. This is usually
preferred to the alternative of removing the old T-Pren joint,
and although the additional height may cause water ponding
this will not affect the life of the joint.
Health & Safety
The normal health and safety procedures for welding, brazing,
soldering and working with lead should be carried out. The
correct protective clothing should be worn, ventilation
provided for indoor work, and hands should be washed before
eating or smoking.