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Decks are a nice backyard addition – if they’re built right

Last month, wanted to educate our loyal readers about decks! We wrote about decking materials and how to stain them, to name a few stories. But Rob Parker, a registered home inspector, has seen enough decks to know whether or not they’ll pass a home inspection. Here’s what you need to know if you’re building your own deck instead of calling a decking contractor.
When buying a home, you should be aware that decks are included in a general home inspection.

Your inspector will provide information about the deck’s condition at the time of the inspection. If you’re considering building or hiring someone to build a deck this summer, you should make note of these requirements before you start building, especially if you plan on selling your home in the near future.

Construction is predetermined by city regulations

If you’re a handy DIYer who’s looking at building their own deck this summer (or fall – it doesn’t have to be a summer job), then you should be aware that most municipalities require a building permit to be obtained before the start of construction and for any structure over 9.2 square metres (100 square feet).

building permit

Not having a building permit approved could delay your decking project and put construction schedules at risk.

Location, location, location

Decks should never be built over air-conditioning units and vents for a fireplace, furnace, hot water heater or dryer because all have codes for required clearances and distances from the deck structure.

deck drawings

A professional decking contractor can draw up a plan that will meet both building codes and avoid these areas that could otherwise be harmful.

Weight issues

Many homeowners have decks built in the backyard so they have a place to entertain. While a deck may be built to accommodate a large number of people, their weight may cause serious problems if it’s not seriously supported by the deck. Unlike interior floors that usually have direct bearing points for the floor joist, a deck may be supported only by connectors, at the house or supporting posts.

In addition to problems associated with weight bearing, it’s quite common to have the ledger board attached directly to the house, with no flashing or spacing to prevent water infiltration. This can lead to rot at the sill plate, band board, ledger and siding.

This deck has seen better days. Lack of joist hangers is what caused this deck to fail.

This deck has seen better days. Lack of joist hangers is what caused this deck to fail.

Are you rethinking your plans to build your own deck?

Don’t forget about water damage

Water also can pocket and then freeze over the winter months, damaging the siding, even vinyl and aluminum. One solution to prevent this from happening is to install a flashing cap. The flashing should go up under the siding at least several centimeters, angled out on top of the ledger, and bent down over the face of the ledger. This will force the water to run off and away from the siding. Another acceptable method is to space the ledger from the house, and fill the bolt holes with silicone or some other sealant prior to inserting the bolts. This will allow the water to drain between the deck and siding.

Decks are susceptible to rotting

Another serious problem involves the potential for rotting of supporting posts and footings. When support posts are put into the footing, and even the ground, they’re prone to rot. The problem occurs when the post is put into the ground, and concrete is poured around the post. Once the concrete has set, the post has established a pocket in which water can collect. The water is absorbed into the post and cannot dry out. In colder climates, the water freezes and can crack the concrete. Additionally, the deck should be bearing on top of the footing and not in it.

Here’s how to prevent this problem from happening:

  • Pour the footing either level or above the grade. Use a positive connection, such as a galvanized anchor base.
  • The post should be bolted to the anchor that’s embedded in the concrete. This will elevate the post off the ground and out of the footing.

It is also acceptable to pour a footing below the frost line, at least 20 cm thick and then sit the post on top of the concrete and tamp (pack) fill dirt around the post. This will allow the water to drain away from the post.

Lowe’s shows us how to dig below the frost line and set the posts on concrete:

Construction requirements

Any deck more than six meters above grade requires a railing, and any set of steps greater than two steps requires a hand rail. Ideally, the railing posts should be through bolted and the railing should be bolted to the deck frame securely. The height of the guard railing for decks less than 1.8 m above grade is 90 cm and for decks over 1.8 m the required height is 1.07 m.

A high deck with decking running perpendicular to the joist may be susceptible to shaking back and forth. This may be due to the lack of proper triangulation. A board fastened to the bottom of the joist from the ledger to the outside band board, running on an angle, can help stabilize the deck. Alternatively, decking running on a diagonal can add triangulation to the deck.

railingsIn addition to proper construction, as with other areas of your home, regular maintenance such as cleaning and sealing or staining the deck with good quality products designed for decks will help slow down deterioration over time and protect your investment.

A good deck can provide a great return on investment, which is why it should be built by a professional. We have an extensive directory of  decking professionals who’d be happy to assist with your decking project!

About the Author: Rob Parker is a home inspector and columnist for the Toronto Sun.

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