Why Junctions are the Weakest Point in Any Roof
The roof covering — whether a bitumen membrane, metal sheeting or tiles — is a relatively homogeneous construction designed specifically for shedding water. But where the roof meets a chimney, ventilation pipe, wall or parapet, a non-uniform junction forms: two materials with different expansion coefficients that move slightly against each other with every temperature change.
In Latvia, with an average of around 200 frost days per year and a temperature range of up to 60°C between winter and summer, this movement accumulates. Sealant ages, cracks and disappears. Without active maintenance, the junction zone typically begins to leak within 5–10 years of construction or the last repair.
Another common problem is junctions that were poorly installed in the first place. Many buildings in Latvia were built with little more than a bead of sealant around the chimney, without a proper flashing system. In those cases, a leak is only a matter of time.
Fact: A correctly installed flashing system lasts 20–30 years. A sealant-only solution lasts 3–7 years. If you have repaired the same junction repeatedly, the cause is an inadequate flashing detail — not a poor sealant choice.
Which Junctions Cause Problems Most Often
Chimney
The most complex junction: four sides, four corners, two different materials. The correct solution is step flashing with counter-flashing built into the chimney mortar joints.
Ventilation Pipes
The pipe perimeter is a constant leak zone. The correct solution is a rubber or metal pipe boot flashing that fully envelops the pipe with a flexible seal.
Roof-to-Wall Junction
Where a pitched roof meets a higher wall or a dormer, a strip junction forms. Without a continuous step flashing, water tracks down the wall.
Parapet
The low wall around a flat roof requires a watertight junction on both faces. The membrane frequently detaches from the parapet and water enters from above or the side.
Roof Hatches and Skylights
The frame perimeter is delicate work — both roofing material and frame metal expand at different rates. Incorrect installation causes leaks at the corners.
Cables and Antennas
Every roof penetration — electricity, internet, antenna — is a potential leak point. Commercial sealing with specialist pipe boot flashings reliably seals these penetrations.
What a Correct Flashing Means — The Technical Details
A flashing is a sheet of metal (galvanised steel, aluminium, copper or zinc) shaped to the specific junction and serving as a physical water diverter. It does not rely on a chemical bond between materials — it forms a lap over which water simply cannot travel upward.
- Step flashing — Used at the junction of a pitched roof with a chimney or wall. Individual metal pieces installed between each tile row or beneath each metal sheet wave.
- Counter-flashing — Laid over the step flashing and built into the chimney or wall masonry joints. Provides the watertight seal from above.
- Drip edge — The roof edge detail that directs water away from the fascia and wall, rather than letting it run down the face.
- Valley flashing — A continuous metal sheet installed at the valley where two roof planes meet — redirecting large volumes of water.
Flashing Repair Process — 5 Steps
Diagnosis — where is the leak?
We locate the source with visual inspection and, if needed, a water test or thermal camera. The leak point is often far from the visible moisture stain on the ceiling.
Assessing the existing flashing
We check whether a flashing exists, what material and form it takes, and whether it is correctly installed. We frequently find that a flashing is entirely absent or was not replaced during the last covering repair.
Preparing the junction
We remove old sealant, damaged metal parts and clean the surface. Where needed, we repair or renew the insulation layer at the junction zone.
Installing or replacing the flashing
We fabricate or fit a ready-made flashing system matched to the specific junction. Everything is finished with appropriate sealant and, where required, additional bitumen torch-applied detail.
Testing and guarantee
We carry out a water test — hosing down from above and checking from inside. You receive a written guarantee covering all works.
Note: If a junction leak has persisted for more than one season, moisture may have penetrated the insulation and timber structure. We recommend a moisture reading to rule out mould and wood rot.
Indicative Prices — Flashing Repair
| Work type | Price from |
|---|---|
| Sealant renewal (1 junction) | €150 |
| Flashing replacement — small chimney | €200 |
| Full junction restoration — large chimney with new flashing system | €300–600 |
| Ventilation pipe flashing replacement | €120–200 |
| Wall junction strip (per linear metre) | €80–150 |
| Parapet junction restoration (per linear metre) | €60–120 |
| Roof hatch sealing | €180–300 |
| Inspection and diagnosis | FREE |
Prices are indicative. We prepare an exact quote after a free on-site inspection.
"Water was coming in at the chimney for the third year running — every time they put sealant on it, and the following spring it was the same again. These specialists explained that without a proper flashing system nothing will hold for long. They installed new counter-flashing — two seasonal cycles have now passed and everything is dry."
Frequently Asked Questions about Flashing Repair
Why does my chimney always leak?
A chimney is one of the most complex junctions in any roof — it passes through the covering and creates a junction between two different materials (masonry and roof covering) with different coefficients of thermal expansion. With every temperature change the junction moves, sealant cracks and water gets in. The correct solution is not applying more sealant, but installing a proper flashing system with step flashing and counter-flashing built into the chimney mortar joints.
What is a flashing and why is it important?
A flashing is a sheet of metal (typically galvanised steel, copper or aluminium) shaped to cover the junction between the roof covering and a vertical structure — chimney, wall or parapet. A flashing is a mechanical, not a chemical, solution: it diverts water away from the junction zone. Correctly installed step flashing and counter-flashing lasts 20–30 years.
How much does chimney flashing repair cost?
Sealant renewal around a chimney: €150–250. Flashing replacement at a small chimney: €200–400. Full junction restoration at a large chimney with a new flashing system: €300–600. Price depends on chimney size, access difficulty and material choice.
What is the difference between sealant and a flashing?
Sealant is a chemical material that fills a gap — it ages, cracks and washes out with rain. Average lifespan 3–7 years. A flashing is a physical metal shield that diverts water — it does not rely on a chemical bond. Sealant is useful as an additional measure, not as the only protection solution.
Can I repair just one junction, or must all be done at once?
Technically you can repair one junction. However, I recommend checking all junctions at the same visit — if the roof is older, several junctions are typically in a similar condition. Doing them together is cheaper than multiple separate call-outs.
Does flashing repair need scaffolding or just ladders?
In most cases ladders or walking on the pitched roof surface are sufficient. Work at tall chimneys or flat roof parapets may require additional safety measures. We assess access before starting and include it in the price calculation.