Quality in Construction Part 1: Whats an eave between friends?

In this blog series we look at a number of aspects that concern modern day quality of construction.

My team had an interesting discussion the other day, despite the fact it concerned not the most exciting of subjects: eaves.

Our discussion focused on do we need eaves in our medium density developments and if so how deep do they need to be and what risk are we taking on if we remove them.

Frank Lloyd Wright - a big fan of large eaves

Developing medium density housing at a gross density  1:200m2 or (50 homes per hectare) where most of the houses are standalone, requires a high attention to detail that needs to be addressed early on. At this density it is the space between buildings and site boundaries that is critically important. In a zero lot line configuration, there may only be 1.2m between homes. We are into design, consenting and contracting on about 20 of these sites at the moment and we are finding every centimeter counts.

Despite New Zealand’s leaky building crisis and a sea of wrapped townhouse schemes having to be re-clad the basic fundamental weather protection of an eave seems to have escaped the lexicon for many designers.

The pressure to remove eaves is a direct result of planning regulations because when applying height in relation to boundary rules, it is the eave that is first to infringe. The easy fix is to clip the eaves which allows you to move the wall closer to the boundary.

In addition, wider eaves increase the percentage of impermeable area on a development site which many zoning regimes seek to control for storm water runoff – so deeper eaves can mean less sell-able floor area.

There are also modern design pressures, what I will term the ‘monolithic architectural style’,  requires solid forms not ruined by punctuating with functional rain protection elements. It does appear many designers now forget about the simple things like how eaves can bring other important benefits like shading during the heat of the summer.

Unfortunately by clipping the eave, you bring water closer to the wall of the home and all openings and horizontal details on it. If there is no eave, water in the gutter is right next to the wall/roof intersection and the effects of pressurisation need careful consideration (I am getting out of my water-tightness knowledge depth here!).  The lesser the depth of the eave the higher the risk of the detail you will be constructing. The higher the risk, the higher level of scrutiny needs to be devoted to ensure quality during detail design and construction.

As recent as last weekend I viewed a property in a popular beach resort that has all the hallmarks of a leaky home – built in the 90’s,  lack of head flashings, monolithic cladding system down to the ground, some cracks, no cavity, and numerous other problem indicators. However, whilst it will probably deteriorate faster over time as any driving weather eventually finds its way through a proven failed cladding system,  this building had no leaks – what it did have was substantial eaves!

I am conscious that the thousands of houses my team has responsibility for developing over the coming years are built to a high quality that lasts; despite budget cuts that could affect maintenance budgets despite; despite gutters that get clogged; despite some failure of some material we don’t yet know about; despite weather-tightness guarantees our contractors provide; and despite how fail safe cladding manufactures market their products as.

To that end we have just implemented a quality assurance process if we are forced to create an eave that is less that 300mm deep. This involves an independent review and inspection of the design and the construction by an independent registered building surveyor (RICS qualified preferred), making these eaves a focus of quality assurance in  the project control meetings and the development and project managers eyeballing the detail and workmanship on site.

Eaves are easy. Eaves work. Long live the eave.

Andrew Crosby


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