The Basics of Deck Footings - Fine Homebuilding (2024)

FAQs

What is the easiest footing for a deck? ›

Precast cement block footings are a popular choice for smaller decks. They are easy to install and do not require any digging.

Each deck support post must be supported by concrete footings. The size of each footing is determined by the tributary load imposed on it. See the diagram below for an explanation of tributary load. Footing must be dug down into undisturbed soil and to a minimum depth of 12-in below the finished grade.

A basic attached deck foundation of 12 feet by 12 feet requires three 12-inch diameter deck footings. It will need at least two more if you build attached stairs. You can use a footing and beam calculator to help you determine how many footings will be best for your deck design.

Plain concrete deck foundations without rebar are acceptable under the minimum standards of construction established in the International Residential Code. However, placing reinforcing steel within footings is a relatively easy and inexpensive practice that can provide increased performance.

Putting gravel under your deck is a great way to add stability and drainage. It's simple to do and provides many benefits, from preventing soil erosion to helping protect the underside of your decking material from moisture damage, especially for ground-level decks.

Deck pier blocks are used in deck building as an alternative foundation to traditional footings. They are placed directly on the ground, and do not require digging or pouring. They come pre-formed with holes for attaching the posts of a deck, making it easy to install.

Footings support a deck's posts and beams and must be spaced and sized accordingly. To figure the deck footing spacing, factor in the size of the footing and beam, as well as the beam's span. In most cases, it's best to space the footings/posts no farther apart than 8 feet in the center.

I prefer to have the top of my concrete deck piers at least 4 inches above the final grade around the piers. I don't want my treated lumber posts buried in the soil, as I've seen them rot and be a food source for termites.

A deck that's constructed without concrete footers — the columns of concrete poured into holes that support the deck — is called a floating deck. A floating deck sits directly on the ground or on deck blocks or deck piers to support the deck.

When measuring for where to place your footers, make sure that the holes will be square with your house and that they are are no more than 8-feet apart in either direction. This is a general recommendation to keep your deck as sturdy as possible.

How do I know what size footing I need? ›

To determine the size of the footing, a simple formula is used: Structural Load (lbs) / Soil Capacity (psf) = Footing Surface Area Required (sq. ft.)

Footing width can vary according to the structure, site, and conditions. Under code, generally, one-story buildings with footings on undisturbed soil with LBVs between 1,500 and 4,000 should have a minimum width of 12 inches. Two-story buildings require a minimum of 15-inch wide footings for 1,500 LBV soil.

In soils with bearing capacity greater than about 4,000 psf, I suggest excavating next to the footing and under it, and placing compacted large gravel into the space. That should be adequate to support the wall. If there's a keyway in the wall, fill it in, and if there's steel projecting from the footing, cut it off.

There are a few options for deck footing, but some are better than others. One constant for each deck footing option is the use of a concrete foundation. Concrete provides a solid, durable foundation for your deck and will last a long time.

A concrete mix of 1 part cement : 2 parts sand : 4 parts coarse aggregate (by volume) should be used for footings.

Precast Cement Blocks

They are a more straightforward and less labor-intensive option. Pros: Ease of Installation: These blocks can be placed directly on the ground without extensive digging or concrete pouring. Cost-Effective: Generally cheaper than pouring concrete footings.

MoistureShield composite decking with CoolDeck Technology doesn't just keep bare feet and paws comfortable in the hot summer sun; it's also splinter-free and slip-resistant.

Usually made of concrete, these footings can be considered the most important part to building your deck correctly. J&W Lumber recommends using QUIKRETE to build your concrete footings.

One of the most common footing types is a concrete footing poured on-site. The concrete is mixed and poured directly onto your job site. The big advantage of this footing type is that it can be customized to any size or shape you need. This provides greater flexibility for your deck design.