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Is a Deck Considered a Structure? What You Need to Know

A deck adds value to the aesthetics and functionality of the property. Having a deck is becoming increasingly important to homeowners, no matter what climate they live in. This is true of commercial buildings as well where decks are used for multiple purposes – from holding impromptu meetings to assigning a corner where people can gather during a break.

Decks are considered to be structures that help extend living spaces by seamlessly connecting the indoors with the outdoors. It is a great way to maximize living space, enjoy the outdoors from the comfort of home, and it also enhances the aesthetic and market value of the house.

This article elaborates on the various ways in which adding a robust and weather-resistant deck structure can create a functional yet pleasing extension to your living space.

Are Decks Considered a Living Space?

Growing needs for ample storage areas and liveable floor plans have led many to consider adding a new structure to their buildings and homes by adding decks.

These decks provide additional living space that extends to the outdoors and have the added advantage of not needing to be heated or cooled like the rest of the house. You can get the best of both worlds – the outdoors as well as the indoors – without sacrificing the comfort of your home.

Residential Decks Are Increasingly Used As Living Spaces

Today’s homeowners are looking for solutions that maximize their living space. Decks are being used for barbecues and family gatherings. Larger establishments have decks on the upper floors of the building, which serve as open-air cafeterias and lounges. Certain decks also have pools built into them.

The book, Ultimate Guide: Decks (link to Amazon) includes multiple deck project ideas with illustrations and step-by-step instructions on adding the perfect deck to your home. Many people use their decks as additional living space to entertain or gather in.

Urban Rooftop Decks Are an Extension to the Building’s Living Area

High-rise commercial and residential buildings have seen the proliferation of rooftop decks complete with urban landscaping, commonly known as green spaces or sky parks. This trend has led to decks being an integral part of the building structure itself.

Decks Bring in Outdoors to the Living Space

A deck technically allows for living spaces in the outdoors. Often these decks may be accessed from the house through doors and from the basement via a stairway. The railing built around the deck area lends the space a semi-private air and apt for entertaining guests or having quality time with family.

It has become very common these days to add garden pots and seating areas complete with a canopy or a pergola on the deck.

Are Decks Considered an Addition?

A deck can be built over any steep area or rough ground that is otherwise unusable. Decks increase your usable outdoor space. Appealing outdoor living space is a welcome addition to any house, and especially so when it is time to put your house on the market.

According to the National Association of Realtors, the average return on investment for adding a new deck is around 71.5%.

Key Elements of a Deck

In the context of a building, a structure is an arrangement of interrelated material objects that form the dwelling set-up of human society. By definition, decks are also structures that add to the overall structural composition of the building.

Like any other structure, decks, too, are designed to bear loads. It can house furniture and withstand heavy foot traffic on its surface. The deck floor is often elevated from the ground and is kept at the same level as the flooring of the house. This ensures a natural transition as one walks out onto the deck from indoors.

Building Restrictions May Be Applicable When Constructing a Deck Structure

Any additional structure to a house, such as a deck, is governed by a set of building guidelines and the by-laws set up by the homeowner’s association.

Building restrictions and guidelines lay out guidance regarding the size and placement of the deck, height of privacy screens, and the distance that needs to be maintained from property lines. The location of the deck may also be dictated by local building and zoning ordinances.   

Decks Have Been Patented As Structures

Deck structures that are adapted for assembly with the help of a supporting frame have been patented as structures. This patent recognizes a deck as a structure adapted for mounting to a frame. The patent goes on to describe the deck structure as one that is easy to assemble, and once assembled, can be securely retained in its assembled state.

Are Decks an Impervious Surface?

Decks are permeable to some degree because of the open slots through which water can drain out. However, the zoning authorities mostly consider any surface or structure that substantially limits or prevents the infiltration of rainfall, snow-melt, or water to be an impervious surface. In light of this understanding, zoning authorities consider decks to be impervious surfaces.

Does the Space Between Decking Boards Make It a Pervious Surface?

While it is not unanimously agreed, some counties consider decks with at least 0.25 inch (0.63 cm) of space between the deck boards to be pervious, while others have considered it to be impervious. If the decks have a permeable layer below the decks, made of soft rocks and gravel through which storm-water can drain out, then those decks are more likely to be considered pervious.

If, on the other hand, the floorboards of the deck are made up of water-resistant materials and the deck is constructed in such a way that the gap between each deck board is almost negligible, and there is no permeable layer of rocks and gravel below the deck, then the deck is likely to be considered an impervious surface.

Does the High Durability of the Deck Boards Make It an Impervious Surface?

In addition to the multiple varieties of decking wood available in the market, composite lumber, PVC decking, and hardwood imports are also readily available.

To ensure durability, composite lumber and PVC decking are two of the more popular choices available in the market. While composite decking is a mixture of wood pulp and recycled plastic, PVC decking is made from 100 percent plastic. They are both very low maintenance and extremely weather-resistant and durable.

This video talks about six such decking materials that are largely available in the market:

However, the high durability and the water-resistant nature of the materials alone do not transform a deck into an impervious surface. A lot of other factors, such as the spacing between the deck boards, the nature of the soil underneath the deck, and the surface area of the deck, all contributes to the impervious nature of the surface. 

Is the Impervious Nature of the Surface Dependant on the Deck Area?

Many counties have upheld that decks that measure up to 200 sq. ft. (18.5 sq. mtrs.) or less do not count as impervious surfaces. If a deck is over 200 sq. ft. (18.5 sq. mtrs.) in area, then one-half of the total deck area counts as impervious.

It is further recommended to have a porous surface underneath the deck area and a minimum spacing between each plank so that any storm-water can get easily drained out.


As a structural addition, decks help bring the enjoyment of the outdoors nearer home. It helps expand the living space and adds to the overall appeal of your property. A well-designed deck can be built to endure harsh weather for years.

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