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How do you replace the lead on chimney stacks?

Updated: May 23, 2023

Removing the lead from the chimney stack

We start by carefully removing all accessible flashing, soakers, apron, and gutter back around the chimney stack and lowering this to the ground to use as templates for new replacements. We then chisel out or cut off the chimney stack with a masonry power saw, the old mortar between brickwork to a depth of 20 mm minimum. Prepare and refix new lead soakers, flashings, apron, and gutter back to chimney stack. We only use code 4 lead on the chimney stacks.


What is a lead apron?

The lead apron is the piece of lead that sits at the front of the chimney stack.

New lead on the chimney stack

This is the first piece you replace when replacing the lead on the chimney stack. We use code 4 lead for this as this is strong enough to deal with this area. When you have two semi-detached properties, you are always best to replace the lead apron on both properties as this is one piece. We see many roofers in Leeds that only replace the section they are working on, leaving a joint in the middle of the chimney stack. This is not ideal as this is one extra area where water can penetrate and cause problems over time. To fix the front piece of lead, you will need some lead clips and lead sealant.


How do you change the lead soaker?

There are several ways to fit lead soakers on your roof. If you have a tiled roof, the lead soakers usually sit on top of the tiles, or if you have a slate roof, the lead soakers will sit underneath the slate. The main object of the lead soakers is to stop water from penetrating through the side of the chimney stack. We also use code 4 lead on the side of the chimney, which is more flexible and hardwearing.


Changing the lead gutter back

The lead gutter back is the essential part of your chimney stack as this is the main area where you find leaks.

This is a roof repair in Leeds

The lead gutter back will need to be code 5 lead as this area will receive the most water. I do see many roofers who use code 4 for this area, and this makes this area of the roof more prone to leaks. We constantly shape the lead gutter back on the scaffolding and make all our cuts where needed, so the piece can slot in nicely when we offer it to the back of the chimney stack.


This piece of lead will also need to be clipped into the brickwork and sealed after to make it fully watertight. It is best practice to curl over the end of the lead so no water can flow over the side.


What is lead step flashing?

The lead step flashing is the pieces of lead that go up the side of the chimney stack and go over the top of the lead soakers. The step flashing stops any water from penetrating the side of the chimney stack, and the pieces should also be clipped into the side.


If I re-lead my chimney stack, how long should it last?

If the lead is fitted correctly, the chimney stack should stay watertight for many years. There might be some maintenance over the years, like sealing the lead back up or if some of the flashings have blown up in the wind. I think a properly leaded chimney stack should last around 50 - 70 years with little to no maintenance.

Who should I get to do the lead work on my chimney stack?

Getting a roofer with experience leading chimney stacks is always best, as it is not a simple job. When it comes to beating the lead into shape, you have to have experience, as I have seen many amateurs overbeat the lead, and when this happens, the lead will become weak.


Is mortar or lead sealant the best to use?

There are mixed reviews about both, but judging both products is the best way to decide this. If a good sand and cement mix is made with some plasticiser, PVA glue, and washing-up liquid, you should get a long-lasting finish. When it comes to sealant, you will need a suitable quality sealant as cheap sealants on the market will crack and eventually leak.


What is the cost of replacing the lead on my chimney stack?

The average cost to replace all four components on a chimney stack is around £750.00. Scaffolding will also have to be added to the price of this job as many jobs will need it.




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