Patination oil and white staining on new lead

Freshly cast and rolled lead is bright. Once it is on the roof, the surface begins to react with oxygen, moisture and carbon dioxide in the air, and it slowly develops a layer of compounds that turns it from silver to a matt, mid grey. That layer is the patina. It is a natural coating, and once it has formed evenly it is the reason lead stays stable on a roof through decades of weather.

The trouble is the in-between stage. While the patina is forming, the surface reacts at different rates in different places. Where water lies on the sheet it reacts one way, and where the surface stays dry it reacts another. Lead that is sheltered under an overhang weathers differently from lead that takes the rain full on, so the same flashing can end up with pale and dark patches side by side.

Why timing matters

The first few months are the tricky ones, and the season they fall in changes how obvious the marks are. Lead laid in autumn meets a lot of rain before the surface has settled. Lead laid in a dry spell can sit bright for weeks, then take its first proper wetting all at once. Neither is a defect, and the patchy look tends to even out as the patina builds.

How long that takes depends on weather and exposure, and we cannot give you a date. Ask your roofer, and read the lead maker's guidance for the product that was used. Meanwhile the lead is doing its job, since the patina has no bearing on whether the joint is watertight. MyJobQuote gives lead flashing over 80 years of life, a long time to look at it.

The white marks come in two forms, and it helps to tell them apart. The first is a pale, chalky film on the lead itself, often in streaks that follow the run of water down the sheet. The second is a white or grey run-off mark on whatever sits below the lead: a brick course, a slate, a painted sill, a stone coping.

Both come from the same early reaction. When rain or condensation sits on bare lead, it dissolves some of the surface compounds, and what dries out is a white deposit. Where the water runs off the sheet onto masonry, the deposit goes with it and is left on the wall as it dries. The effect is most visible on light stone and new, pale brick, and least on dark slate.

Is it harmful?

For the roof, white bloom is mostly cosmetic. It is not a sign that the sheet is failing, and it does not mean water is getting through. On the wall below it can look worse than it is, and a clean, mild rinse often shifts fresh deposits. The caution is for the person doing the cleaning: lead and its compounds are not something to handle carelessly. Wear gloves, keep washings away from ponds and vegetable beds, and never scrub dry material into dust.

Streaks that stay put are the ones to look at more carefully. A heavy white crust in one spot can mean that water is sitting there, perhaps behind a lap, along a poorly shaped drip or where the lead is in contact with damp timber. In that case the cause is a detail to fix, not a surface to clean. Our answer on leaking lead flashing explains how to tell a cosmetic mark from a leak.

Patination oil is a protective coating made for new lead. It is brushed or sprayed onto the clean, dry sheet after fitting, and it leaves a thin film that gives the surface an even, slightly darker grey from day one. While it sits on the sheet, the lead underneath weathers more slowly and uniformly, and less white run-off reaches the wall below. It does not stop lead weathering, and it does not form the patina for you. It manages the awkward stage.

The oil works as an appearance measure. It is no substitute for a good detail: it will not seal a bad lap, close a gap at a chase or hold a flashing in place. The things that keep the water out are the code of the sheet, the clips, the wedges, the rolls and the fall. The oil sits on top of all that.

How we handle it

Maker's instructions govern every product, so we follow the data sheet for the oil in use, including how clean and dry the lead must be and how it is applied. Lead needs to be free of dust, grease and surface water first. The coat goes on along the finished flashing with a brush, and care is needed because oil on a clay tile, slate or pale render leaves a mark of its own. We mask and wipe back as we go.

The weather decides when it can go on. A cold, damp or windy day is a poor day for a coating, and the leadwork can be completed first with the oil applied when conditions suit. Our guide to leadwork in winter and wet weather explains how that sequence works.

Whether to oil is a judgement about what you can see and what will run onto what. Four situations push the answer towards yes.

• The lead is visible from the street, such as a bay window roof, a dormer cheek or a chimney flashing against clean brick.
• Run-off from the lead falls onto light masonry, pale render or painted work that would show a streak.
• The property is in a conservation area or is listed, where the look of the roof is part of what is protected.
• The owner simply wants the new work to blend in sooner.

In the opposite case, hidden lead gets little benefit. A valley lining tucked between two slopes, a back gutter behind a chimney or lead under a covering is out of sight, and run-off from it falls onto tiles or into a gutter where no one will see it. The oil there is a small cost for little gain, and many roofers leave it off.

Conservation areas and listed buildings

Bognor Regis has conservation areas, and Arun District Council's appraisals describe the character of each. On a listed building the council's conservation officer may care about the colour and finish of any visible metal. Check with Arun District Council's planning team (or the authority for your town) before using any coating on visible lead on a listed building. On a conservation-area house, like-for-like lead renewal is normally routine, and an even finish can make new work look right from the street.

When you read a quote, check whether the oil is mentioned. It sits inside the total price along with the lead and the labour, and you are entitled to ask for it to be included or left out.

If your lead has already gone white, or you chose not to oil, the next question is whether to clean it. The short answer is that you can, gently, and that you can also leave it.

Cleaning the lead itself

Plenty of owners find the marks fade as the patina evens out and rain washes the surface. If you want to speed that along, use clean water and a soft brush on a dry day, and rinse down to a gutter that drains properly. Stay off ladders and roof edges; leave anything above head height to your roofer. Do not use a wire brush, an abrasive pad or a harsh chemical cleaner. They scratch the sheet and strip the patina you are trying to build. If you are unsure about a product, check what the lead maker recommends first.

Cleaning the wall or tiles below

Fresh run-off marks on brick or stone are easier to shift than old ones. A soft brush and water often does the job, but masonry varies, and a cleaner that suits brick can mark limestone or soft render. Test a small, hidden patch first. For old, set-in marks or delicate stone, ask a specialist or the council's conservation officer before you try anything stronger.

Keeping water moving also helps. A blocked gutter, a chase full of moss or a flashing lapped the wrong way lets water sit on lead, which is when deposits form.

Bare lead that has weathered to a matt grey is not neglected lead. It is lead that has finished its first season and settled down, and it looks the part on an older roof.

Oil is a surface treatment, and some marks point at faults that no coating can cure. Knowing the difference saves money and time.

Marks that are not the patina

A crack in the sheet looks like a thin dark line, often at a fold or a clip. Oil will not close it, and the water that passes through it will carry on. If a white mark sits at a crack, or the sheet is lifting at an edge, the repair is lead work, not a coat of oil. Our short answer on lead cracking explains what causes it.

Dark staining on the wall beneath is a different matter. It may mean the gutter above is overflowing, or that water is spilling off a lap and running down the face. Soggy, stained plaster inside points the same way. These are leaks, and cleaning the outside will not stop them.

Choosing the repair, not the coat

A good survey looks at the lead before it looks at the colour. The laps, clips, wedges and chase all get checked and photographed. The verdict is plain: sound lead needs nothing but time, tired lead may need a patch, and worn or badly fixed lead needs renewing. Oil then comes into the conversation as a finish for the new work, not as a way to hide the old.

The cost of the oil is small next to the lead and the access, and it sits within the total on the quote. The lead roofing and leadwork page describes the work we do. Lead that is detailed well and left to weather will usually look better each year than a coating alone can make it.