Flashing is an integral part of any roof. This weather resistant barrier prevents water gaining access through joints on your roof. Areas such as chimneys, vents, walls that abut roofs, windows and door openings all present areas for potential water access.

Prior to the use of sheet flashing, many techniques were employed to prevent water gaining access to properties. Angling shingles away from joints, chimney placement and even access to the chimney to manual move the water. The introduction of lead flashing in the mid 1700’s meant malleable, weather resistant sheets of metal could be cut to the required size and manipulated to form the exact shape to fit the areas most needed to prevent water penetration.

There are 3 main types of flashing:

• Chimney Flashing
• Step Flashing
• Apron Flashing

Chimney Flashing

The point where your chimney meets your roof is a particularly vulnerable to water gaining access if not protected correctly. Chimney flashing is applied to the point where you roof and chimney meet, step flashing is commonly used in this area.

Step flashing

Step flashing refers to the pattern created when cutting the lead and positioning it in an overlapping pattern resembling a staircase. By using the lead in this way the lead is manipulated to penetrate into the brick courses. Areas where a lower height roof meets a house wall, a roof meets a chimney or where a conservatory roof meets the house wall.

Apron Flashing

The most common type of flashing is apron or cover flashing. It is highly versatile and therefore perfect for; areas where there is abutting brickwork on flat roofs, around chimneys, areas where your roof meets brickwork, on conservatories and around bay windows. It can be used on both slate and tiles.

Which lead should be used?

Once known as milled lead, rolled lead is available in various codes. The codes basically refer to the thickness or the lead.

Code 3 – Is generally used for lead soakers, as it is a thinner and lighter. These unseen water proof sections (soakers) provide protection underneath tiles or slates. Used in areas such as; valleys or hips between two roof slopes, slates or tiles on curved roofs or swept valleys, at a part wall junction between two adjoining roofs, at a party wall junction . The soakers can be different sides for any one of these areas. This code is not advised to be used as main cover flashing as too much movement in a roof could cause it to split.

Code 4– Is the recommended code for lead flashings, the thickness provides both versatility and resistance to fatigue and splits from contraction and expansion whilst being also malleable. On occasion, it may also be used for soakers, and is certainly the most common type of code used within the roofing industry. It is very well suited for both lead hip flashings, lead roof valleys, and is versatile and robust enough to be used as cladding, or small roofs and wall sections.

Code 5 – Can be used, where deemed necessary, for the same aspects as Code 4 , with the exception of soakers, due to its increased thickness. On older larger properties that have more extensive sized valleys, Code 5 could be the more suitable option. Other aspects where Code 5 will be used is with
pitched gutters where there is an increase in normal water flow, usually due to higher roof elevations or roofs that have multiple elevations, or a combination of both. Old properties, and especially Listed Buildings that have degrading stone gutters, can be repaired internally using Code 5 sections that are lead-welded using expansion joints, this is also true of bay top roofs.

Code 6–Code 7-Code 8 – Are primarily used only for roof coverings due to their relevant thickness and strength.

Lead Flashing Length

Lead sheet for flashing should be no longer than 1.5 meters. The overlap of the flashing should be a minimum of 100mm. Lead work that is cut longer than this may split and fracture with contraction and expansion. Certain weather conditions, exceptionally high flashings may require an increase in overlap to avoid water creep.

Fixing Lead Flashing

There are three ways of fixing lead flashing. The more traditional method involves rolling a small strip of lead, usually 25mm or less in to an oval shape, forming a bung or ‘chock’, this should be just wider than the mortar chase, the chock is then driven in to the are to sit just below the surface of the bricks to form a wedge.

The alternatives methods are to use nylon flashing clips or hall clips. If a large run of flashing is being installed these may be quicker and easier to use. And finally the more advanced and technical lead- welding.

The term flashing isn’t as commonly recognised as other roofing aspects but to put it simply a flashing is a thin piece of resistant material which is designed to avert the passage of water, the flashing acts as a weather resistant barrier. A type of flashing gets their name by the location of uses or shapes.