Get your flat roof ready for autumn
Autumn is when a flat roof is revealed. The rain falls for hours, leaves settle in the gutters, and the joints that just made it through the summer suddenly have standing water on them for days. You can do most of that now, while the roof is still dry and the weather is good.
Clear drains and roof drains first
It's the cheapest job, and it saves the most roofs. Leaves and moss collect around the well, the water stagnates, and then it finds its way down the nearest weak joint instead of out to the drain. Check it again after the first real autumn storm, that's where the leaves come from.
Follow the five transitions
The roof surface itself is rarely the problem. It is the transitions that give up first:
- Joints and overlaps in the roofing felt where the glue has come loose
- Upstands against masonry, fire ridge and neighboring building
- Skylights and light boxes where the flashing has come loose
- Penetrations for ventilation, exhaust, antenna and solar cells
- Edges and transitions down to the gutter
If there are cracks, blisters or loose edges in any of those places, those are the ones you need to address, not the entire surface.
How to tell the difference between wear and tear and damage
Wear and tear you can live with
Faded color, some peeling of slate granules and small moss growths on the north side. It looks sad, but the roof is tight.
Damage that needs to be fixed before winter
Open joints, blisters that give way when you press, cracks at the edges and water that stands on the surface the day after rain. These are the areas where frost continues to work its way through the winter.
When can you seal it?
The roof membrane should be applied to a dry roof, and it should be exposed to dry weather for a few hours afterwards. The surface will be dry again in about 1 to 2 hours, depending on the weather. The windows of dry weather will become shorter throughout October, so the earlier in the fall you apply it, the more flexible you are with the day.
The membrane is 1-component and ready-mixed. It is applied in one layer with a roller or brush, without a gas burner and without primer in several steps, so a garage or carport roof is typically completed in a morning.
What it costs to wait until spring
A leaky joint doesn't let water into a nice, confined area. The water runs along the rafters and insulation and emerges somewhere else inside, and in the meantime the insulation gets wet. Wet insulation doesn't insulate, and it doesn't dry out on its own under roofing felt. That's where a repair costing a few thousand kroner turns into a roof replacement.
Frost does the same thing to a crack as it does to a crack in asphalt. The water settles in it, freezes, expands, and makes the crack wider. One winter is enough to turn a hair-thin crack into something that can be seen.
What you can achieve in a weekend
- Sweep the roof and clean drains and wells
- Scrub off moss where there is any and let the roof dry.
- Place the membrane on edges, risers and around skylights first
- Roll the surface while the edges are still fresh.
If you need to calculate how many buckets your roof requires, you can do it directly on product page, where the calculator is based on square meters.
