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A behind the scenes look at a pool and landscape project in Ontario’s Muskoka region

Structural concrete

5_pool sequence 5- the blasted shelf
The ‘shelf’ (bunker floor) is 5.5 m (18 ft) below grade. This involved drilling and blasting 914,442 kg (900 tons) of granite.

A complete set of engineered structural and hydraulic plans were used for the placement of three tractor trailer loads of rebar and all 900 m3 (1177 cu yd) of cast-in-place concrete used throughout the project.

Much of the pool construction was simplified by creating the shelf in the granite bedrock. The base was still pinned to the exposed granite that was left intact, while some of the smaller blast rock was left insitu as a base for the pool foundation. An extensive drainage system was installed to carry groundwater, which is continually seeping from the granite face to the tree bed gardens created below.

Cast-in-place construction was used to pour all of the pool, spa, shallow lounging area, surge tanks, bunkers, and cantilevered decks. All of the concrete was pumped using a standard boom pump with the exception of the cantilevered decks on the lakeside of the cottage. A line pump was used for these areas.

Dealing with challenges

Pumping a large volume of concrete in such a remote area presented a number of challenges. For instance, during half-load season, trucks could only be loaded with 3 m (9.8 ft) of concrete (normally trucks are loaded with 9 m [29.5 ft]). To overcome this obstacle, the ready-mix company brought full loads to the end of the gravel road and then used a shuttle truck to move the 3-m (9.8-ft) loads to the build site. Normally, concrete must be placed within 60 minutes of batching; however, a number of additives were mixed into the concrete at the plant, and on-site, to meet the engineered concrete requirements over a longer time frame.

Gravel was stock piled on-site while the ground was still frozen. Once half-load season ended in mid-May, more gravel was brought in for backfilling and grading.

cantilevever deck on cottage , lakeside
The structural cantilevered decks that surrounded the pool and cottage were relatively easy to construct. The only difficulty was working with harnesses and keeping a constant watch for any safety concerns while working on the edge of the cliff.

The pool portion of the project was built in layers, similar to the construction of a high-rise building. Soil and mechanical engineers verified the progress at all of the important stages of construction. With the pool base being 5.5 m (18 ft) below grade, the local survey crew assisted with locating structures, as running string and plumb lines were not accurate enough.

The structural cantilevered decks that surrounded the pool and cottage were relatively easy to construct. The only difficulty was working with harnesses and keeping a constant watch for any safety concerns while working on the edge of the cliff.

Concrete slabs were poured and large granite flagstone tiles were laid around the pool and wrapped around the cottage to create patios and walkways. Developing multi-level patios suited the site’s topography and aided in the creation of different entertainment spaces. In a secluded section, located beneath the main patio and set before the backdrop of the forest, a lower-level patio provides a relaxing lounge area with a custom firepit. Together with the soothing sounds of the nearby negative-edge pool, the perfect place for the quintessential Muskoka summer evening was created.

Part of the project involved running kilometres of conduit for the various subtrades that would follow the installation of the structural components. Electrical, lighting, automation, irrigation, audio, gas lines, plumbing, drain lines, and all of the pool equipment had to be imbedded in the structural concrete. Detailed plans were drawn up to ensure nothing was missed. Having to core, chip, and install conduit lines after the fact is expensive and time consuming. When in doubt, it is always a good idea to run extra lines and chase pipes.

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