Design & build: My, what a great roof you have

We designed our house with a flat roof to maximise our outdoor living spaces while creating a low profile home, tucking into the bush surrounding the site. Photo / Ben Crawford

The Block NZ 2012 winner Ben Crawford and his girlfriend Kylie are building their dream home. Share their proud moments and pitfalls here every week.

The most common question we get about the design of our home always relates to our decision to have a flat roof. Without fail, the conversation leads to one about water tightness.

So with the roof of our bedroom pod nearing completion, I wanted to dispel the misconception that a flat roof is a leaky roof. But why do we want a flat roof?

The short answer is design and practicality. Our philosophy has been to work with the land, not against it. So when it came to the house's architecture, we wanted a home that complemented its surroundings by being as natural and as low-profile as possible.

A flat roof was the ideal solution. It provides clean, sharp and modern lines like the rest of the house and also enables the bedroom pod, in particular, to nestle perfectly under the bush canopy, an effect that wouldn't be possible with a steeply pitched roof.

We were also conscious that the section is in a valley surrounded by trees, so sunlight will be at a premium, particularly in winter.

We pondered our outdoor living areas and spent ages observing how the sun tracked across the site. We realised the sunniest spot was where our living pod was, which was when Kylie came up with the brilliant idea of creating a roof-top deck.

This is where flat roof designs excel. They are practical and flexible, allowing you to get more use out of your property. We have been able to create an additional 60sq m of outdoor living space and at the same time maximise the available sunshine hours. Had we gone with a pitched roof we would have a smaller home and some pretty shady outdoor living spaces.

The Nuraply 3PM system is a double layer torch on membrane system. Photo / Ben Crawford

Other possible applications include creating a green roof, using it as a car park or providing built-up city environments with outdoor gardens.

Now to that water-tightness myth. After preliminary research we were assured that with good design, great products and ongoing maintenance, a flat roof can, in fact, be more watertight than tiles or iron.

We had the design aspect under control and I've happily committed to regularly clearing out the gutters. So that left the final aspect: finding a great product and applicator to make our flat roof a reality.

That task turned out to be quite simple. A quick Google search for "flat roof experts" found a company called Nuralite.

After thoroughly reading its website it was clear they were indeed experts when it comes to flat roofs.

After all, you can't be in business for more than 40 years if you're not good at what you do. Plus, I discovered that its flagship product, Nuraply 3PM, is the most specified and popular torch-on roof membrane system in the country.

All of the lap joints are welded together to create a perfectly watertight roof. Photo / Ben Crawford

I always like to know as much as I can about a company and how its products work, so I arranged to meet managing director John Simmons.

He loved our design and how we planned to use our roof space and immediately confirmed the Nuraply 3PM system was the perfect roofing solution for our home.

Simmons then showed me how Nuraply 3PM works, explaining that it's bulletproof because of the double layer system.

First, an adhesive is put on to the plywood roof structure before the first bitumen membrane layer is applied. Then the second layer, which has a natural mineral chip finish, is heat-welded to the first layer and is offset from the runs of membrane below to prevent any leaks.

A flat roof house on Waiheke using the double layer Nuraply 3PM system. Photo / Ben Crawford

Finally, all the joints are welded together, creating a perfectly watertight and robust roof with a back-up system, providing complete peace of mind even in the heaviest of rain.

I was sold. But what's the point of a great product if it isn't installed correctly? Simmons recommended I meet Terracon Industries, one of Nuralite's approved applicators on the North Shore, to see if its expert team would be available to work on our house.

But that's a story for another day. A very nice story, in fact, where we all live happily ever after.