Lead flashing where a conservatory meets the house

A conservatory is a separate structure leaning on the house. The two move at different rates, as the temperature changes and as the ground settles, and the gap between them has to stay watertight through all of it. The roof slopes away from the wall, so rain from the house wall above runs straight down onto the joint.

That makes it the busiest detail on the whole roof. The flashing has to follow the slope of the conservatory roof, stay tight to the wall and allow movement. On a sloping roof it is usually formed in steps, each one tucked into a course of brickwork. Our answer on a conservatory roof leaking at the ridge covers a related joint at the other end of the same slope. Water that gets in at this joint tends to show up inside the room, well below the point where it entered, which makes the source hard to guess without a ladder. Moving the furniture away from the wall and checking after heavy rain is a good way to tell the wall joint from the glazing.

The leadworker cuts a chase in the brickwork, a slot in the mortar joint, then dresses the lead into it and fixes it with wedges, a method set out in our answer on lead wedges. The lower part lies over the conservatory roof frame and glazing bars, finished with a lip that sheds water clear of the joint.

On a lean-to roof the lead runs up the slope in stepped pieces, each overlapping the next, with the lower edge held down. Royston lists lead codes 4, 5 and 6 as suitable for flashings, and the choice depends on the length of each piece and how exposed it is. Our guide to lead codes explains how the codes are marked and what they weigh. A hipped or Victorian-style roof needs more shaped pieces than a plain lean-to. Where the conservatory wall is rendered or pebble-dashed, the lead is set into a chase cut into the finish and the brick behind, so the finish is repaired neatly afterwards.

The usual faults are lead that has pulled out of the chase because the pointing has failed, a joint closed with sealant that has dried and split, and lead that has cracked from movement. Damp patches on the house wall inside the conservatory, drips at the top of the glazing bars or stains running down the plaster are the visible signs.

A conservatory roof that has been replaced without renewing the flashing can also leave a gap. The new roof sits at a slightly different height, and the old lead no longer reaches the new surface. If your conservatory started to leak at the wall after a recent roof change, that mismatch is high on our list of things to check, along with the glazing bar caps and the cills. Moss and debris trapped behind the lead in the valley between roof and wall can also hold water against the joint, so we clear that before judging the flashing.

If you are replacing a conservatory roof with a solid one, the Planning Portal's guidance on conservatories is that the new roof has to meet the Building Regulations on structure, energy efficiency and ventilation. Your building control body, either the council's team or a registered building control approver, deals with it before the work starts. Our solid conservatory roof regulations guide explains the process.

The flashing is part of that job, and where the work is notifiable we deal with the notification. For a glass or polycarbonate roof, ask your building control body if you are unsure, because the answer depends on the roof you are fitting. Replacing only the lead at the wall is a repair, and the survey tells you which route your job takes. Keep any approval paperwork somewhere safe, because it is the proof that the roof was signed off if you sell. Let your building control body know early if the new roof will be heavier than the old one, since the frame may need checking.

Published lifespans make a difference here. HomeBuilding gives a typical polycarbonate conservatory roof about 10 years and the Eco Experts give 10 to 15 years, while MyJobQuote gives lead flashing more than 80 years. So a lead flashing in good condition may outlast the roof it was built to serve.

When we replace a conservatory roof, we check whether the existing lead can stay, whether it needs relaying to meet the new roof, or whether it has failed. Once the survey is done, you receive our quote in writing as one overall price. For the wider picture, see our conservatory roof replacement page and the lead roofing and leadwork page. If the lead is sound, keeping it saves both money and waste. A new roof laid over lead that is failing wastes the new roof's first winters, so it is worth settling the lead question at the same time as the glazing.