The city of Austin has set up impervious coverage restrictions for the footprint of all buildings falling within the city limits. The size of your building including sidewalks, patios, driveways, and anything impervious to water seeping into the ground is set at a maximum of 45% of the total lot size. As a simple example if you have 10,000 square feet of land to build on your building shall be no larger that 4,500 square feet. Some properties in Austin have been grandfathered in and exceed this limit, some others have received a variance for additions.
When adding a pool, impervious coverage is one of the first things your pool builder should inquire about before designing your pool. If you are under 40% coverage you are in a good situation. Anything over 40% becomes trickier to design around, but there are several ways to accomplish this. Keep in mind that anytime you approach the 45% mark, you’ll need to hire a survey company to calculate your new impervious coverage before and after construction to meet city requirements as you approach 45%. Typically you’ll need a before calculation and survey to submit prior to construction along with a new calculation after construction to be submitted before your final inspection is approved. Talk to your survey company about a package deal for this service.
Some ways to address impervious restrictions are removing existing walkways and or removing existing structures. Sometimes taking out a sidewalk and some stone planters can allocate enough space to add an addition. Other times more severe and costly remedies are required. Currently wood decks are calculated at 50% however the rules are constantly changing and vary depending on which inspector your get. Many other pervious materials such as crushed granite, pervious pavers, and pervious concrete are not typically recognized by the city of Austin. That is why in tight areas, great design becomes an even more important approach to the form and function of your pool.
The good news is, the water area of your pool will not count as impervious coverage. Only the coping and decking around it. So if you have a small amount of space for your outdoor living area, the right design should still be able to give you the form and function you desire.