You do not need to be a roofer to know that lead has been used in roof construction for hundreds of years. The main reason for this is that lead has a durability to it that means it can perform its waterproofing function for decades without requiring any repair or renewal. However, there are circumstances in which repairing the lead works on a roof become necessary. In this article, we look at the composition of lead and describe some of the problems that can arise that create the need for roofing repairs by your local roofers.
The Characteristics of Lead
Most lead sheet that is used on roofs in the UK nowadays is milled lead sheet. The lead sheet has to be manufactured to a high standard of quality, the details of which are set out in BS1178. Having said this, continuously cast lead sheet has gained popularity in the UK roofing market over the last few years. However the lead is manufactured, it is a metal that has a high coefficient of expansion. This means that it will expand in the heat and contract in the cold. It is essential, therefore, that this is taken into account when the lead is fixed to the roof. The fixings should not prevent expansion or contraction but should still be sufficiently secure to hold the lead in position. This can be achieved through the use of fixing retaining clips within the joints to permit expansion/contraction in conjunction with fixings along the free edges to keep the sheet securely attached.
Lead is also susceptible to corrosion if warm air penetrates from the house through to the roof. This can cause white stains running down the joints and a whitish powder accumulating beneath the lead. The best way of avoiding this problem is through the creation of a ventilated air space underneath the material that is used for the roof decking.
Lead Sheet and Flashing Issues
The following is a list of factors that are likely to give rise to the need to carry out remedial work to the lead on a roof;
- The presence of rippling or splitting
- Utilisation of pieces of lead that are too large
- Inappropriate fixing restricting the ability of the lead to expand/contract
- Worn or poor fixings
- Signs of corrosion, as highlighted above
- The presence of an inadequate underlay
If any of these features is apparent the next decision that will have to be made will be whether to carry out repairs to the roof or to renew the offending parts of it. Repair or Renew
As a rule of thumb, if lead roofing sheets or flashings are generally perceived to be in a reasonable state, with, perhaps, only a few relatively insignificant breaks it will probably be sufficient to carry out some modest repairs. This is obviously the most economical way of dealing with problems, so long as your roofing contractor is confident that it will provide a lasting solution. However, if the evidence thrown up by a roofing inspection suggests that the problems are more severe, the only viable solution may be to have the lead works renewed. Whilst this is likely to be more costly, to attempt to patch up lead works that are beyond repair will represent a false economy and will be likely to result in further problems in the foreseeable future, which will then require proper remedial measures.
The lead works on a roof are an essential part of its structure and are key to the roof’s efficient performance. Keeping the lead sheets and flashings in a good state of repair is therefore imperative if you want to keep an effective roof over your head.