Bespoke Leadwork

How to Install Lead Cover Flashing Correctly?

Lead Cover Flashing

The 4 Stages of Installing Lead Cover Flashing

Lead cover flashings are one of the most common lead flashings used on all buildings and if installed correctly will last more than 50 years. Installing lead cover flashing can be broke down into 5 main steps:

  1. Grind out joint or create new chase
  2. Install lead cover flashing
  3. Fill joint or seal joint
  4. Patinate lead flashing

1: Grind Out Joint or Create New Chase

To grind out a joint or a new chase a 125mm grinder with a masonry disc is required. If installing lead cover flashing into a brick wall, then it is easiest to grind out the mortar joint in between the bricks. The mortar is generally relatively soft, and it easily allows you to grind out a straight line. If creating a new chase into concrete wall, you will want to measure the height of the proposed chase from either end then mark a straight line for you to follow with the grinder. A chalk line is a good way to create a straight line, however you can also use a long straight edge such as a level.

Whether the chase is new or old the depth of the chase needs to be a minimum of 25mm deep and 10mm high. Once the chase is cut out, it needs to be thoroughly cleaned out, a electric blower is ideal to do this.

2: Install Lead Cover Flashing

Lead cover flashing is generally made from 20kg or 25kg lead sheet. When deciding on the width of lead to use, you need to measure the height between the bottom of the roof upstand and the bottom of the chase you have cut out. Once you have this measurement add on 25mm which is the amount you will be turning into the chase. It is very important that the lead cover flashings do not get installed in longer lengths than 1.5m due to the thermal movement of lead, if installed in longer lengths the lead flashing is likely to fail. If the area required to flash is longer than 1.5m then you can lap the lead flashings, the lap should not be less than 100mm.

Once the lead flashings are installed into the new chase you will need to fix the lead, to do this you can use either lead wedges or stainless-steelwall clips. Lead wedges are small strips of lead approx. 25mm wide which are folded until the thickness of the wedge matches the height of the chase, the lead wedge is then hit into the chase with a hammer and then finished off with a blunt chisel until the wedge is completely wedged into the chase securing the lead flashing to the wall. These wedges or wall clips should be used every 450mm.

3: Fill or Seal Joint

Once the lead cover flashing is installed it is time to fill and seal the chase, this can be done one of 2 ways, either with mortar or sealant. A mortar joint is sometimes preferred when installing into a brick wall for aesthetic reasons, however, experience has shown that the mortar can crack and fail due to the thermal movement of lead. Therefore, we recommend using a polyurethane sealant that can accommodate thermal expansion and creates a much stronger waterproof seal between the wall and the lead. It is important to ensure the sealant joint is smooth and flush with the chase and that there are no sections of the joint that are not connected to both the wall and the lead. It is recommended to use masking tape along the chase both above and below the joint to ensure a neat sealant joint.

4: Patinate Lead Flashing

The final stage of installing lead flashing is to patinate the lead, this prevents the lead from oxidising and turning white. To do this you need to use Patination oil, simple pour some patination oil onto a cloth and wipe all the lead ideally along the ‘grain’ of the lead. It is important not to get any patination on the new sealant joint as this may compromise the sealant. Patination oil can stain other surfaces especially slate, therefore you will need to take extra care not to spill or drop any oil onto anything but the lead. Once the patination oil is applied allow it to dry before touching the lead again.

Professional Installation of Lead Cover Flashing

Whilst installing lead cover flashing can be broken up into 4 simple stages if you want a professional finish with a guarantee that the lead flashing will not leak or fail then you will want it to be installed by a skilled tradesman.

At Bespoke Leadwork we have a team of highly qualified lead workers who specialise in all aspects of lead work, lead flashings and lead roofing. We can install lead flashings that not only keep the water out but look good and compliment the rest of the building.

Contact us today for more information or your obligation free quote.