Lead flashing is one of the most important ways to reinforce a home’s seams or joints. However, sometimes you can’t get an optimum fit because something’s in the way. This article will explain how to navigate around a window sill when installing lead flashing.Â
Upstand
The main way window sills will change flashing is how the chase and drop work. The drop is the part of the lead that goes up the wall, and the chase is where it enters the brickwork to keep the flashing in place. Normally an angle grinder is used to cut 25mm into the gap in the brickwork to make room for the chase, but if you are flashing directly underneath a windowsill it’s advisable to only carve out 20mm in order to avoid compromising the window frame.
In addition, depending on how close the window is, you might not be able to complete a normal-sized drop. Normally this goes up 150mm from the flashing, or two levels of bricks before being chased. But a windowsill might restrict you to only 75mm of drop.
The lead is moulded into the right spots using dressing tools. These work it up the drop, and then a chasing wedge and mallet are used to work it into the carved area in the brickwork. This should be done as with normal flashing, only taking into account the reduced drop and chase.Â
Dormers
On the other hand, if there is absolutely no room between where you need to flash and the windowsill, you will need to take a different tack. This might happen if the window is a dormer window for instance, where it is sticking directly out of the tiled roof. Fortunately, the windowsill juts out so it can help protect the flashing from water where an upstand is not possible.Â
There is one thing you need to make sure of however. The flashing can’t go so near the sill that there’s a real risk of accidentally touching it if you lead out of your window. Lead is, of course, toxic. Make sure that when resting your hands on the sill or gripping the bottom that the lead is far away.
