Comments on risk of flat roof with internal gutter

It is no doubt that flat roof incorporating internal gutters is regarded as a high risk design feature.

The economic risk and return theory is generally applied to building design as well. While risk of leaking is higher, flat roof can often gain higher usage of limited building platform, achieve a better view, achieve desired exterior looking, hide unsighted features, bring more light into interior space and so on.

As long as well designed, well built and well maintained, just as any other exterior features, flat roof with internal gutter can be well performed or even out-performing many other type of roofs. It is problematic only when either design, or construction or maintenance side has got any problems, such as no consideration was taken by the designer for future maintenance and replacement, incorporating overly complex junctions, substandard materials being used during construction, poor construction workmanship, minimum or no maintenance by occupants and so on.

Flat roof incorporating internal gutter is a building element, which inspectors should keep good eyes on rather than simply relying on inspection tools only. It is a typical feature, which to be assessed from design, construction, historical and current performance, likelihood of future major issues, expected serviceable life and other perspectives. A competent building inspector should deliver a lot more comments than simply stating “leaking or not”.

Why there is a common “perception” that stucco houses have “no value” comparing to “other” building finishes?

First of all, common perception does not necessarily mean correct. Otherwise, there is no need to have any scientific study. It is actually more to the other end, i.e. common perception is often wrong.

This common perception comes from a summary of following common misunderstanding:

Most of leaky houses are “monolithic” houses;

Many monolithic houses are clad with “Stucco”;

Stucco is a high maintenance material;

Stucco houses cost fortune to reclad;

Stucco has got poor ventilation ability, therefore moisture can be easily trapped within framing;

If I need to make a correct statement, I would put it in the following way:

A poorly designed, poorly constructed and poorly maintained complex timber framed house clad with direct fixed stucco may have “no value” if exterior wall framing timber is under-treated.

We have to look at a stucco building from many perspectives, such as design, construction, maintenance, building envelope simplicity, timber treatment, cladding system, location, wind zone and etc. before we can make any judgement.

To explain where this common perception comes from, consider the following workout:

Many externally complex houses leaked;

Many externally complex houses used stucco;

So stucco causes leaks.

There are a lot of reasons why complex buildings have used stucco as their cladding system. I will do some separate writings for that topic. But should people somehow decided to use other type of cladding, e.g. weatherboard as the main cladding system back during that leaky building era, we now many have a totally different common perception.