A deck is attached to the house and exposed to the elements, so it can seem incredibly strong and durable.
However, each deck is designed to hold a specific amount, and going over this amount can cause structural damage.
Calculating how much your deck can hold can help you make various decisions regarding your home.
Why should I know how much my deck can hold?
The most obvious reason for wanting to know how much a deck can hold is if you want to put something heavy on it.
For example, many people want the option to add a hot tub to their deck, but these items can be incredibly heavy, so it’s important to ensure that the deck can support it.
Knowing how much your deck can hold isn’t only important for placing heavy items on it, though. If you like to entertain and you want to have a large party on your deck, you may need to make sure that the deck can support a big group of people.
Knowing what your deck can hold is also a good idea if you live in an area that sees a lot of snowfall. Snow and ice can be surprisingly heavy, so before you start building your deck, you’ll probably want to make sure that it can hold the weight of several feet of snow.
How much can a deck hold?
How much a deck can hold depends on a number of factors relating to that particular deck. However, on average, a deck can hold about 100 pounds per square foot. This is only an average, however. When a deck is built to code, the code only requires that the deck can hold a minimum of 50 pounds per square foot.
Live Load
When you’re figuring out how much weight a deck can hold, many people will talk about live load. This is the term for the weight of the people or things you place on the deck.
The dead load is the weight of the structural pieces of the deck itself, such as the boards you stand on. The live load weight capacity of a deck is about 80% of the entire weight capacity, and the dead load is usually about 20%.
This means that, if your deck can hold 100 pounds per square foot, about 80 pounds of that is live load, and this is the actual amount of additional weight the deck can support.
Footings
There are several factors that need to be considered when you’re figuring out how much your deck can hold. One of the most important is footings.
Footings are the pieces of the deck that touch the ground and support the weight of the deck itself. Footings must, according to code, be a certain diameter, and there must be a certain amount of them, for the size and shape of the deck.
If your deck has the minimum number of footings and they’re the minimum diameter, the deck might only be able to hold 50 pounds per square foot.
However, if there are more footings or the footings are larger than necessary, the deck can often hold more. What hardware was used to join the footings and the deck can also increase your deck’s maximum weight capacity.
Lumber Type
Lumber type can also help you determine how much your deck can hold. Most decks are made with either southern yellow pine, a combination of red pine, redwood, and cedar, or a combination of pine, spruce, and fir.
Southern yellow pine is the strongest, and it can help your deck support far more weight. Cedar, redwood, and the combination of spruce, pine, and fir, more commonly called SPF in the construction industry, are also quite strong.
Soil Type
When people think about how much a deck can hold, they often consider the construction of the deck itself, but what type of soil or ground the deck is placed on can also make a big difference.
Although a deck might be structurally sound enough to support a large amount of weight, if it’s built on loose soil, sand, or clay, it can sink if enough weight is added, which can cause structural issues.
Loose soils are considered to be the default for deck building, just in case any or all of the footings need to be placed on looser soil.
Decks built on loose soil must have a soil bearing capacity of at least 1,500 pounds per square foot. If the soil is too loose and can’t come up to 1,500 pounds per square foot, you may need to pick another area to build the deck.
However, if your deck is built on rock or bedrock, the soil bearing capacity can reach 12,000 pounds per square foot, and decks built on hard surfaces like this are unlikely to ever slip or sink.
