July 1, 2011
By Sherry Hayes
You’ve decided to take the plunge and install a new inground swimming pool in your backyard. The pool has been chosen, the contractor is booked for installation and the excitement is mounting in anticipation of a fun-filled swimming season. Before the fun can begin, however, you must properly evaluate the grade of your property.
Simply put, the grade is the incline or slope of your property, which can vary from place to place in your yard. It is crucial the space for your new pool is properly planned or you might be faced with unpleasant surprises, or worse, additional expenses.
There are three important—and often overlooked—grade-related questions you need to answer before construction begins. They are not as glamorous as thoughts of poolside parties and elegant water features, but they must be asked to avoid turning your dream backyard into a nightmare.
Evaluating your backyard
As a layperson, it is easy to misread a grade or assume your backyard has only a minor slope. To avoid making this rookie mistake, try this simple exercise. Tap four stakes into the ground, one in each corner where the pool and surrounding surfaces will eventually sit. String separate lines to each end, as well as diagonally between the corners, making sure all lines are level. Once the level lines are stretched across the area, you will get a clear picture of what you’re dealing with.
What you described to the contractor as minor grade changes could be much more of a slope than you imagined, posing a variety of issues for your pool project. That slight grade could differ anywhere from 304 to 609 mm (12 to 24 in.) or more, which can become a slippery slope in the end.
The existing grade is designed to maintain water and drainage flow; therefore it should not be altered. However, when installing a pool within a sloping area, it is virtually impossible not to change the grade. Nevertheless, appropriate adjustments must be made to maintain water flow as your property was originally designed. You cannot impede the flow of water within your property—or the surrounding development for that matter. Each situation will be different and should be discussed with your pool installer before construction begins. It will be necessary to determine how to place the pool and surrounding hard surfaces in accordance with the grade and any drainage concerns. Your personal needs; budget and style preferences will also factor in the equation.
When planning your pool, you must think beyond the footprint of the pool wall and include the room needed for other aspects of the pool area, such as seating. For example, a 4.8 x 9.7-m (16 x 32-ft) swimming pool with a 1-m (3-ft) deck around the pool’s edge covers a minimum space of 6.7 x 12 m (22 x 40 ft), assuming there are pool steps in place. Once lounge chairs and a dining set are factored in, additional patio space will be required within that footprint.
When discussing your needs with the pool representative or installer, be sure to discuss the grade of your entire property. The area for the pool and surround is just one piece of the puzzle. The balance of your backyard must also be considered during the planning process. Errors in pool placement or elevation can impact any or all other elements such as additional hard surfaces, amount of steps required and garden beds.
If you intend to have a separate deck or patio area, for example, you must determine whether the two hard surfaces will be installed at the same level or terraced. The placement of a rear door on your house and its elevation off the existing grade can also influence the area’s overall flow. For example, a door that sits 609 mm (24 in.) above the grade will require the installation of several additional steps, to allow proper access to the backyard from your house. This, in turn, decreases the amount of usable space for other features.
Most backyards slope away from the house toward the property line. If possible, consider placing the pool at the lowest grade within the specified area. A grade difference of 406 to 533 mm (16 to 21 in.) allows for a perfect bench-height retaining wall for additional seating around the pool. This layout provides both function and esthetic value.
You must also be aware of and adhere to any applicable building codes and local bylaws while planning your pool and backyard, before any construction begins. Generally, your local city planning or bylaw offices will have the information necessary to assist with specific requirements.
It is far better to know all aspects of the installation well in advance. Proper planning will help avoid last-minute stress and potential expense. It isn’t in your best interest to have a 3-m (10-ft) deep hole in the ground, only to realize you have an elevation issue that requires a costly, time-consuming solution.
While oversized lots generally have enough space to feather out grading issues, the typical subdivision lot often does not, especially when the pool and surrounding hard surfaces (e.g. deck, steps) sit in close proximity to the property line and/or any swales that should be left undisturbed. Swales (ditches or lower ‘v-shaped’ areas) direct water flow through or around the property and neighbourhood. They generally sit at, or near, your property line. Your property may also have additional swales within the backyard to direct water flow away from your house. Crescent-shaped swales are commonly found in backyards and usually sit approximately 2.4 to 4.5 m (8 to 15 ft) from the rear foundation line of your house and run to each side of the property. This swale must also be addressed to avoid water sitting or backing up on your property or any surrounding properties.
When working with sloping properties, the existing grade will likely have changes throughout or follow a gradual drop. When dealing with these circumstances, there are a variety of options available to address a sloping property. The most common is a retaining wall with drainage accommodations. A retaining wall is a feature that is designed to ‘retain’ something—in this case, the pool wall or the earth that has been exposed, which remains at a different height than the pool area. Strength and durability are important factors when choosing the appropriate materials. Bear in mind, you must abide by your local building codes and bylaws with any grade and drainage changes.
Wall placement is important to the overall layout of your backyard. First, determine whether the wall will become part of the landscape or hidden from view. There are several design options available, each of which can turn a negative issue into a positive feature or even a focal point. By consulting with a knowledgeable, experienced landscape designer, you can better understand how a wall can become a highlight of your backyard as a functional element, rather than a detriment to your pool area.
Retaining wall materials can vary substantially based on the strength required and placement. Large boulders or manufactured locking wall systems are common options. Either material is generally acceptable provided it is deemed functional for the specific need. The choice should be based on the following requirements: personal preference, budget and accessibility. In terms of accessibility, materials that require a forklift or similar compact machinery to move also need a minimum space to be able to navigate the equipment.
If using boulders, they must be placed at the appropriate time—whether before, during or after pool installation—which will vary depending on the project based on accessibility. It is generally easier to install boulders during the excavation process to avoid potential damage to the pool and hard surfaces. Boulders should be reasonably uniform with smooth top surfaces while manufactured walls are best with a minimum depth of 304 mm (12 in.) on the cap or coping if being used for seating. For additional interest, surrounding gardens and steps leading from an upper patio to the pool area provide both functional and esthetic value.
The use of manufactured materials is contingent on manufacturer’s specifications. Be aware of any height or load-bearing restrictions/limitations when choosing materials. Vertical stacking walls do not generally have the same strength that locking, step-back wall systems can provide.
Creative planning opens the possibilities for multi-usage walls, especially when elevations permit multiple levels within the backyard. If space and drainage permit, the final placement of the pool wall, and ultimately the pool decking, can vary within the area of installation. The choices range from the upper, middle or lower area of the grade. Your own personal use should ultimately decide which area of elevation should be used. The end result determines the height and length of the retaining wall.
When working with a sloping property it all comes down to proper placement of each element to maintain flow from area to area. Take the appropriate steps when planning your backyard and you are sure to have years of enjoyment splashing around or just relaxing in your new swimming pool.
Sherry Hayes is a freelance writer and an award winning landscape designer. She owns Landscaping with Style, a design firm in Hamilton, Ont. For more information visit her website at www.landscapingwithstyle.on.ca.
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