01
Roof sealing
The joints on a roof sealed properly, around chimneys, walls, skylights, vents and pipes, which is where most leaks actually begin.
in short
AltHome seals roof junctions across Kerry, Cork and Limerick, where roofs meet chimneys, walls, skylights and pipes, which is where most leaks start. Failed flashings are replaced with lead dressed into the mortar joints, with soakers where needed, and pipes get proper collars, rather than being smeared with mastic. A typical house takes a day, in dry weather.
what decides it
A roof leaks at its joints
The main field of a roof, the slates or tiles laid in rows, is very good at keeping water out. The places water gets in are the joints: where the roof meets a chimney, a wall, a skylight or a dormer, around vent pipes and flues, along the ridge and hips, and where two roofs meet. Those are sealed with flashings, collars and mortar, and they are what ages first. The most common bad repair we see is a failed flashing smeared with black mastic or silicone. It stops the leak for a season, then shrinks, cracks and traps water behind it. Sealing a roof properly means fixing each junction with the right detail. Lead flashings are cut into a mortar joint and dressed down over the roof covering, with soakers under slates or tiles where the roof runs against a wall. Pipes and flues get a purpose made collar or lead slate rather than a ring of sealant. Skylights get the flashing kit made for them refitted. Ridges and hips are rebedded or dry fixed. And we go around every junction on the roof, not just the one that is leaking, because they are all the same age and the same workmanship.
When sealant is the right answer
There are places where a modern sealant or liquid system is correct: some metal roof laps, certain flat roof details and small cracks in otherwise sound materials. We use them where the manufacturer and the detail call for it, not as a substitute for a flashing that should be lead.
the work
What is included in roof sealing?
- Inspect every junction on the roof: chimney, walls, skylights, pipes and ridge.
- Remove failed mastic and sealant back to sound material.
- Cut in and dress new lead flashings, with soakers where needed.
- Fit proper collars or lead slates around pipes and flues.
- Refit skylight flashing kits and rebed or dry fix ridges and hips.
- Photograph each junction before and after.
4 steps
How long does it take to reseal roof flashings?
You get in touch
Tell us where water appears and send a photo of the roof if you can. We answer the same day.
We come and look
We check every junction and price the ones that need doing.
We seal it
Usually a day, in dry weather, and nothing is left open overnight.
You sign it off
You get photos of every junction and the guarantee in writing.
next door
What goes around it
Junctions fail alongside the parts of the roof around them.
asked
Roof sealing: common questions
Is silicone or mastic a proper repair?
On most roof junctions, no. It shrinks, cracks and traps water. Lead flashing dressed into the joint is the lasting repair, and we use sealants only where the detail is designed for them.
How long does lead flashing last?
Properly fitted, it can last for decades. It usually fails because it was never cut into the joint, the mortar has fallen out, or it was never dressed down properly.
Why check junctions that are not leaking?
They are the same age and workmanship as the one that is. Fixing them on the same visit saves another call out next winter.
How much does it cost to replace lead flashing?
The length of flashing, the type of junction (chimney, wall, skylight, dormer) and access set the price. A chimney flashing with soakers and a back gutter takes longer than a simple wall abutment.
Why not just seal the leak with silicone?
Silicone and mastic hold for a season, then shrink and crack as the roof moves and trap water behind them. Lead dressed into the joint moves with the roof and lasts decades.
quote
Get a fixed quote for roof sealing
Tell us the address and where the water is getting in. We work across Kerry, Cork and Limerick. We ring you back within one working day.
085 220 1422 · info@althome.ie
Written by the AltHome crew. Last reviewed September 2026.