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.

After a jubilant first week of action on site and a buoyant beginning to this week's building, things turned a tad mediocre as our second week of construction drew to a close.

Kylie and I had been singing from the rooftops about how smoothly our earthworks were going. And they were.

The building platform had been cut without a hitch, the subsoil drains were in and we were already a week ahead of schedule. The sun was shining and life was good as our piling contractors arrived on site.

Because of the types of soil on our section and with the stream running right through the middle, our house needs to be built on timber piles as opposed to a concrete-slab foundation. Essentially, it'll be on stilts, but pretty ones once we finish with them.

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The earlier assessments made by the geotechnical engineers found our timber piles would need to be driven up to five metres deep to reach foundation-worthy soil.

Given parts of our house will eventually be more than two metres above the ground, the starting length of the piles would range from six to nine metres. We were intrigued how these giant poles would be put into place, so we pulled up a front-row pew to watch the action unfold.

Before the piling could begin, four test sets had to be done in strategic places around the house and witnessed by our structural and geotechnical engineers because they needed to ensure their calculations were correct when it came to the on-site construction.


A 9m long pile being thumped to depth. Photo / Ben Crawford

We had been nervous about this part. What if the geology of our section didn't match the theoretical models, throwing our entire plans out the window? Fortunately, after the first four piles were driven to depth and everything had gone as expected, the engineers gave the green light and the remaining 42 piles could be thumped in.

The bedroom side of the house was finished within a day. We'd been worried that all the thumping and vibrating required to set the piles might ruin our stream and the months of hard work would be in vain. However everything held up superbly - thanks to the amazing skills and care of the contractors, Ground And Pound.

Then it was on to piling the other side of the house, our driveway and the retaining walls. The Ground And Pound boys said they would smash it out in a day and, after witnessing their efficient operation on the bedroom pod, I had no doubts. I even rang mum and dad to tell them our foundations were successfully in. Obviously I spoke too soon.


Left: A huge pile getting lowered into place. Right: Checking the set of the pile to ensure it's meeting the engineer's specification. Photo / Ben Crawford

Everything started out well but things slowly turned to custard. Well, actually, a boggy, muddy mess. This part of the section has always been wet and will be addressed eventually with a lot of drainage.

However in the short term, a 14 tonne digger and this type of soil don't mix, and pretty soon it was stuck in the mud, unable to reach a couple of areas requiring piles.

As the digger's tracks churned up the earth with I-don't-want-to-watch-any more ease, it revealed just how average the soil below our garage area is. The plan had been to lay a normal concrete slab over a standard base course with a piled footing along the stream edge, but it became apparent we'd need a different approach.

Luckily our geotechnical and structural engineers were able to recommend a new design that same day.

Called a piled raft slab, some extra piles were driven below the garage floor to create a foundation grid, on which the eventual concrete slab and supporting ground beams will sit, creating a perfectly sound parking area. The added bonus was that it solved our immediate issue of getting the digger to the rear of the section, as it was able to crawl along the top of these new piles and finish the job.


Left: One of the huge piles being vibrated into the ground. Right: The locations of our piles being pre drilled. Photo / Ben Crawford

I guess in the big scheme of things it could have been a whole lot worse, especially when the earthworks stage of any build is the biggest unknown. So we've come off pretty lightly, losing only a couple of days from the schedule and only adding small figures to the overall costings. But we've learned a valuable lesson about this building caper; it's never over until the fat lady sings.

• Find out more about Ben and Kylie's dream home at ourdreamhome.co.nz

For more information on the Kiwibank First Home Buyer's Guide visit: kiwibank.co.nz and search for "first home".