Window Eyebrow

Provides weathertightness deflection of rainwater away from important flashings

Windows require holes in the cladding. These holes must be flashed so they are as waterproof as the cladding itself. Typically windows are square so require a diverter along the top called a head flashing so rain water running down the wall from above is diverted over the window safely. The hole also requires Jamb flashings down the sides and a sill flashing to divert the water from the window out over the cladding safely.

In this case I will be explaining the head flashing.

It was defectively installed and allowed water to track in around the ends and only had a small overlap to the window flange. As the window has no soffit protection rain water was able to wick up behind the plaster and wick in under the ends of the head flashing.

A useful upgrade is to fit an eyebrow. Fitted at the right height and covering the entire head flashing it takes over the function of deflection and provides a weathertight detail that only requires occasional paint. This detail does not require sealant.
 

No head flashing

Old Insulclad cladding

On the face of it you cannot understand how this detail would be compliant - no head, Jamb or sill flashing on this 1988 Insulclad window. But it has lasted? Why? Because the framing used in 1988 was treated against decay. Yes its leaked, yes the Insulclad has radially cracked around some windows, and yes it has been regularly painted. Never sealed. But it can't go on like this as boron treatment leaches out and over time decay sets in. Fact is the Building Act only allows claims within 10 years and due to the treatment level the framing would not have become damaged in such a short time. It has obviously been leaking BUT without moisture probes the owner would not realise.

Harditex head flashing

Deconstructed

I have chosen this particular window to show how things go wrong. The window had a set of 'mouldings' around the head, Jamb and sill as beautification's. Looked nice and passed the visual pre-purchase inspection. On the face of it the mouldings should have added an extra line of defence against water entry. But the probes when installed told a totally different story. Wet framing and decay. Leaked and framing was only H1 insect resistant not decay treated.

What is wrong is the head flashing ends are cut into the Harditex sheet allowing pathways of water in over the ends, around under the ends and through the Jambs as they were not air or watertight (or sealed).

Due to movement the Harditex has cracked and split allowing even more water entry.

All of this was covered over and out of sight so passed the visual inspection.

Eyebrows were too late but after some repairs they are what is required.

 

Corner window eyebrows

Provide deflection away from the head flashings

They look nice too. But the function of the head flashings is to deflect rain water away from the head flashing so no wicking water can get in and wet the framing.

Prior to the eyebrow the owner had reported water dribbling out the head in the corner. The head flashing was not weathertight at the miter.

Eyebrows solve many of the problems with poor head flashings as it stops rainwater wicking and getting in around the ends.
 

Arched and stepped windows

Head flashings do not work if vertical

Head flashings are intended to divert water running down the cladding over the face of the window. In theory and in low wind zones they work when horizontal - in this case only the very top of the arch is horizontal. As the curve sets in the head flashing becomes vertical allowing water to flow straight in. This water is not picked up by the two side stepped windows so leaks in along the tops of the two side windows and down the Jambs.

Windows being cuts through the claddings are in effect wall gutters. They collect water and discharge it onto the window corners and down the framing.

Wet framing becomes decayed framing.

In this case the owner was lucky enough to have 'wet frame boron treated timber' which has some early decay resistance. Decayed but not that serious. Intervention included RotStop, eyebrows and new Jamb sealants. Monitoring shows its improvement. 

Arched window eyebrow

Curved head flashing

This small addition, the eyebrow, stopped leaks on every window.

Curved plaster over faceted window

Eyebrows corrected head flashing defects

Faceted windows give great panoramic views but are impractical to flash properly. Each head flashing must be mitered so they remain weathertight at every joint, and the ends.

Impossible to achieve. Impossible to remain weathertight. Impossible to maintain. Yet persisted with. To the detriment of owners.

To correct weathertightness something as simple as an eyebrow is sufficient. Attractive and practical. Should have been part of the build specifications. Now is.