Lead

Laid correctly, lead can last over 100 years. Unlike other materials it can be shaped and joints can be welded. Because of these advantages, lead is widely used for flat roofs, roofs over oriel, bay or dormer windows, ridges, gutters and flashings.

Lead in use

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Lead flat roofGreyfriars RoofingLaid in stepped sections or bays to allow for expansion, all joined by raised rolls.
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Lead flashingsJohn GilbertUsed here to make a long lasting complicated junction
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Lead worked to cover a skylightJohn GilbertA good long lasting repair

Typical Problems

Lead can become damaged through:

  • general old age
  • cracking from being laid in such a way that the metal cannot move as it expands and contracts as temperature changes
  • foot damage causing sharp debris to pierce the lead
  • corrosion pinholes caused by acid run off from algae, moss and some types of wood
  • condensation dampness due to poor ventilation under the lead (an increasing problem as we keep our homes warmer)
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Temporary flashband repairHistoric Enbironment ScotlandMay last long enough for you to commission a proper repair

Water penetration can also occur if there are:

  • inadequate overlaps at lead joints or joints are poorly made
  • puddles caused by inadequate falls (slopes) on roofs and large gutters 
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Defective flashing Historic Environment ScotlandIf lead is overworked it can thin so much that it will crack and open up

Getting the best lead repair

Lead must be laid and formed correctly, so if you are carrying out repairs,

  • try to ensure the company is a member of the Lead Contractors Association
  • check if individual leadworkers carry a CSCS (Construction Skills Certification Scheme) with a blue craft skill card for 'Roofer-Specialist Leadworker'
  • check that your specification follows those set out by the Lead Sheet Association
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Defective leadwork on flat roofJohn GilbertPatch repairs are an attempt to over cracks. Note ineadequate height of steps and overlaps.

Specifically, check:

  • sheets are not too long for the purpose
  • sufficient overlaps are left at joints
  • correct weight of lead is used for the purpose
  • appropriate types of joint used for the purpose
  • adequate ventilation is used under the lead with ventilation gaps left in sarking boards underneath 
  • lead is laid with the right falls to rain water outlets
  • lead sheet can move (e.g is not fastened all the way along its length)
  • fixed with copper or stainless steel nails and with copper, lead or stainless steel clips
  • patination oil is used to coat the lead and prevent staining on slates, tiles or brickwork below
  • use of building paper between lead and sarking to allow lead to move

White marks on lead are lead carbonate which is poisonous. It is your duty to make sure you use a contractor who is properly equipped and experienced to handle such dangerous materials.

Lead thicknesses 

Lead thickness is expressed as a code, the higher the number, the heavier the lead. Generally speaking, the larger the area to be covered, the heavier the lead to be used.

  • Code 4 and 5 lead can be used on flashings
  • Code 6, 7 and 8 is commonly used on flat roofs
  • Use at least Code 6 for gutters (Code 7 or 8 on longer and wider valleys)

Alternatives to lead

For flashings

  • zinc, copper and other metals -  zinc can also be welded but is less easy to shape than lead - can last at least 30 years
  • bitumen felt compounds (“Nuralite”) have lasted for over 30 years however they do become brittle with age
  • mortar fillets may be used for skew flashings but are prone to cracking
  • polymer based materials may be used for flashings – a variety of trade products are available with life lengths from 20 - 30 years but some of them are nearly as expensive as lead

 More about flashings

For flat roofs 

Where there is a risk of theft of lead, you can also consider getting the lead marked with "Smartwater".

If you are in a listed building or conservation area, you will need consent to replace lead with these materials.

More about flat roofs

Further reference

Lead Sheet Association 'Pocket Guide for Installers of Rolled Lead Sheet'

Lead Contractors Association