Drainage With Stone Cills

Stone cill drainage for aluminium doors and windows is an important issue.  Unlike aluminium door and window cills stone cills have a different construction and designs.  They are also drained differently which is the subject of this article.

The biggest difference between stone and aluminium cills is their design.  An aluminium cill is made from hollow extrusions with thermal breaks.  A stone cill is solid piece of stone which is then cut and shaped to the required size and design.

How is an aluminium door and window drained with a stone cill?

As the stone is a solid piece they do not have drainage channels that go through them.  For the stone cill to offer effective draining of the water that runs over them they have a specific design.  As mentioned in our other technical articles aluminium doors and windows are designed to let water in through the gaskets.

The most common method of draining aluminium doors and windows with stone cills is to face drain the aluminium frame.  The excess water drains back out of the frame through specially designed drainage holes away by the stone cill.

On the diagram there is a groove underneath the stone cill which is called a drip groove or throating.  As water will travel upside down and toward the wall it needs diverting to the ground.  When the water reaches the drip groove gravity takes over and the water drips to the ground.

Reveal Doors and Windows minimum recommended projection beyond the face of the stonework is 40mm.  There should also be sufficient distance between the drip groove and the face of the stonework of about 10mm.

 Stone cill drainage for aluminium doors and windows

Choosing the right stone cill design?

Stone cills vary by supplier in sizes and shapes.  Some are as shown above with sloping sections to allow the water to run away from the aluminium doors and windows around the cill.

There are some stone cills that are flat on the top which should be avoided.  These do not drain water away and the water can sometimes pool.  The pooling or standing water can then cause damage to the stonework which can be expensive to repair.  The biggest threat is if the water gets in to the interior of the wall cavity.


Closing Comments

Proper consideration for stone cill drainage for aluminium doors and windows needs to be given.  For existing stone cills the correct aluminium door and window frame needs to be selected to ensure that aesthetically and functionally they will work.  Our advice would be when selecting the stone cill for a new building the cill and drainage needs to be considered together.

By getting this right at the start you can alleviate any expensive mistakes such as damage caused by water entering the building which ultimately could damage the fabric of the building and its interior décor.

For additional information please do not hesitate to contact Reveal Doors and Windows on 0113 386 9207.  We are always happy to help you and discuss your requirements in further detail.