Lead roof repair
This is a short guide on how to repair a lead roof, or repair a lead bay roof. I will be showing you a technique used by professional roofers that will provide a better and longer lasting repair than a DIY store paint on solution alone. Mostly I will reference a bay roof window as this is the most common lead roof leak encountered by the average homeowner, but of course it will also work on larger lead roof too.
An article and videos on other types of flat roof repair can be found in the links at the bottom of the page.
Bay Windows & Lead roof leaks
A bay window can come in many shapes and sizes, quite often though the covering is either lead or felt. Typically when they start to leak the first sign is water dripping onto the window sill, a brown stain on the ceiling or water running down the internal window.
What causes leaks in lead bays ?
The most common cause, especially in old houses is fatigue cracks. As the lead gets hot and cold it expands and contracts, this is quite normal and allowances would have been made when the roof was initially laid to allow for this. However most leaking lead bays are original to the house being built, meaning they can be 50 to 100 years old. That’s a lot of expansion and contraction.
Needs repair – A fatigue crack is basically a split in the lead caused by the above process. Once the crack is present and sufficiently big, it doesn’t take long for the water to find its way in. This one is very large and has been repaired before. Often however they can be quite fine and difficult to see without close inspection.
Is there a lead roof alternative ?
Increasingly these days with lead theft becoming more of a problem some people are moving away from lead, and certainly if you’re talking about small roofs or lead bays, fibreglass is a viable option. To see what fibreglass roofs look like see the Fibreglass bay roofs page.
When to repair a lead roof that’s leaking
If the lead seems reasonable, look closely at the overall condition and count up how many splits or holes there is and balance out the cost of the repair(s) against the cost of replacement with either Lead or Fibreglass. If the roof has several previous repairs it may not be worth the effort, especially if guaranteeing the job for a customer.
How NOT to repair a lead roof
Quite often we see bitumen or other similar paint on repairs applied, these are a waste of time and money for the following reasons.
- Short term solution – Any paint, bitumen or sealer no matter what the manufacturers claim will either dry out and crack, or simply be pulled apart by the force of expanding and contracting.
- Makes a good repair more difficult – Therefore more expensive. A good rule of thumb is that any sort of paint-on roof sealer should be avoided on lead in any circumstance, unless it’s an emergency.
Best paint on roof coating and water proofer
As mentioned above, painting straight onto lead can make a good repair harder work and therefore more costly, but in an emergency use an acrylic based paint on sealer like Evercryl – Cromapol – Acrypol – Roofacryl – Acryflex. Contrary to the instructions on the tin it helps if the roof is dry and free of grease and dirt. Another alternative is a small smear of normal silicone sealant, but again a clean and dry surface is best.
How to repair a bay window or lead roof without soldering
Most commonly this is the technique that is used to fix a leaking bay roof window or flat lead roof, but it can also be used in almost all leaks where a split or hole in the lead is the culprit.
DIY and Trade repair – This video on lead roof repair shows a long lasting repair for a lead roof. The use of heat is required.
More videos on flat roof repair, some without the use of hot flame can be found in the links at the bottom of the page.
Preparation – Remove any old previous repairs if possible, repairs on top of repairs are never a good thing. Wire brush the lead all around the fatigue crack or hole, taking care not to breathe in the lead dust, try to get upwind if possible and wear a mask. Clean a minimum of 50mm all around the area to remove the lead oxidisation.
Next – Cut a piece of Flashing Tape to size with a Stanley knife, there are many different manufacturers on the market of varying quality, most people though are familiar with ‘Flashband’. For those who don’t know it’s essentially a very thin Aluminium type tape coated with a sticky self adhesive Butyl type coating. Other brands are available – Bond it – Cromar – Bitu bond – Black Jack – Aqua seal
Adhere with heat – I blowlamp the tape down onto the lead at this stage, It will stick quite well of its own accord especially in the summer, but you can’t beat heating the surface of the tape to get a really good bond. Use gentle heat on a small hand held blow lamp working on about a 10cm patch at a time and rubbing it down with an old rag will do the trick.
Safety always – A good alternative to a blowlamp is a heat gun on a low setting if you have access to power. Remember that even though there is no naked flames to worry about they can also start a fire especially as you can be lulled into a false sense of security.
Finish – I like to seal the top of the repair with an Acrylic fibre reinforced paint which adds another layer of protection but also hides any burn marks you may have gotten from blow lamping the flashing tape down. It’s not vital but finishes the job off nicely. A sealant like this is probably the best paint on repair for lead in emergencies, brands are Evercryl – Cromapol – Acrypol – Roofacryl – Acryflex
Warning Important – When working with naked flames
Make sure you are insured to work with naked flames, let the blowlamp warm up before using or tilting, some blowlamps flare when tilted or the gas canister is really full, be aware of this. Also do not work with a blowlamp underneath flammable things like soffits, gutters e.t.c. Be aware even if Insured there can be a lot of wriggle room if you haven’t taken adequate safety measures! Have a fire extinguisher on hand always.
Also see…
- How to fit a new Lead roof – What lead you buy and how to use
- How to install Lead flashings – Full instructions
- Flat roof repair – Nearly all types of flat roof repaired
- Bay windows – Roof covering choices for bay roofs
- How to fibreglass a bay roof – Lay your own fibreglass bay roof
- Fibreglass bay roof – A superb lead alternative
- Roofing tools – Some of the tools I use day to daily