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Do Grade-Level Decks Make Sense for Your Client?

Article-Do Grade-Level Decks Make Sense for Your Client?

Tony Tallec/Alamy Stock Photo Lounge chairs on ground level deck of modern house
Low-lying decks could be a consideration for your client’s decking needs. Here’s some important information about the grade-level process and a few things you’ll need to keep in mind.

A grade-level or low-lying deck is a box frame that’s topped by floorboards and supported by joists. This type of deck can be placed on any level surface, anywhere in the yard. If the deck is placed next to the house, but not attached, it’s considered a platform. Attaching the deck to the house makes the house look larger and is an easy transition from home to landscape.

Grade-level decks can be a more affordable alternative to hardscaping. They are faster to frame than elevated decks as there are no ledger or lateral-load connections to deal with and no requirements for footing depth.

Decks that are less than 30 inches above grade can be easier to build for several reasons. They usually don’t require railings, steps or guardrails and they may not require a permit. According to information from, decks under 200 square feet and/or shorter than 30 inches high that are unattached to a property don’t require a permit.

A major consideration for grade-level decks is ventilation. Since the ground under a platform deck will get wet, dampness is the enemy of this type of structure as it can lead to mold, rot and decay. Leaves and other debris that collect underneath the deck reduce lumber’s drying potential, making the choice of material used an important one. Because joists and beams will be close to or in contact with the ground, a grade-level deck requires pressure-treated lumber with an AWPA UC4A tag, according to the Journal of Light Construction. When framing rim beams and in-floor beams so a deck can hug the ground, you’re going to use a lot more joist hangers and other metal hardware than when cantilevering joists over beams. Since the hangers are going to be close to the ground, there is a potentially greater risk of corrosion. One option may be to use stainless steel hardware, but keep in mind that most hardware manufacturers don’t recommend installing their hardware below grade.

Since there are moisture and ventilation concerns regarding grade-level decks, it makes sense to address what you can before you cover the area. You can begin by sloping it away from the building the deck will be attached to, to create proper drainage direction. If possible, dig the earth below the deck frame deeper than the surrounding area, then backfill with permeable materials that will help to absorb precipitation.


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