Reliable drainage for your house roof

Roof and drainage

A reliable drainage system is the foundation of a durable house. Installing gutters, external window sills and similar elements is a must.

A light blue house with scaffolding on which a wooden roof is being installed.

Roof drainage

A really good roof drainage system is important for a house, because it is not only storms that cause problems. Even light summer rain can bring large amounts of water. It is said that rainfall of one millimetre per hour on a roof with an area of 100 m² produces about 500 litres of water if the rain lasts 5 hours. Good roof drainage is therefore essential if you want to protect your house from moisture damage.

Factors that affect roof drainage:

roof pitch
amount of rainfall
exposure of the building to wind
capacity of the drainage system...
...and the presence of emergency (secondary) drainage
temperature differences
resistance of the waterproofing layer to standing water

Reduce the risk of damage

To make roof drainage reliable and reduce the risk of damage to the house and its structure, you can take several measures:

Think about the greenery around the house – trees increase the risk of drain gullies becoming blocked.
Provide emergency roof drainage that takes over when the main drainage system is not working.
Check the drainage system regularly. Check, for example, the gutters, gullies and silt traps in the ground connected to the roof drainage.
Check that the drainage system does not leak anywhere. Look for gutters that are not connected to downpipes, or downpipes that are not connected to the pipes in the ground.
Check regularly the safety overflow.
When renovating the drainage, make sure it is correctly connected to the waterproofing layer.

A light blue wooden house with a newly laid board-on-board timber roof (faltak).

A downpipe bracket is installed on a white wooden facade with a gutter hook screw.

Installing gutters and downpipes

Roof drainage elements such as gutters, downpipes and external window sills carry water away from the roof and the house when it rains or snow melts. It is important that they are correctly fixed with screws that withstand the outdoor environment and are suited to the conditions.

Gutter hook screw – installing gutters and downpipes

Gutters and downpipes are fixed to the facade with gutter hook screws. The gutter is installed along the longer sides of the roof – gutter hooks are used for this, and the gutters are then clipped into them. We recommend that gutters have a fall of about 0.5 cm per 1 metre towards the downpipes so that the water drains away.

Screw the gutter hook with a cordless screwdriver set to a low torque directly into the pre-punched holes in the hook.

Installing external window sills

An external sheet-metal window sill prevents rain from getting in between the window frame and the wall. It is very important for the durability of the window. Its slope matters because it drains water away – so it has to be installed correctly to avoid moisture damage.

For installation on a wooden facade we have external window sill screws. The screw has a Fibercut tip, which makes it easier to drive in and minimises splitting of the wood. The screw also seals against the sheet metal and protects the joint from the weather. Remember to pre-drill the sheet metal of the window sill when installing!