Can You Put a Sunroom on Top of Decking?

While it may seem logical to assume that because decks are typically built over foundations, adding a sunroom on top of decking would be a piece of cake. This couldn't be farther from the truth. For starters, while decks can be built over foundations, they are typically not specifically engineered to carry the sort of extra load that a sunroom will present.

Building a sunroom over your existing deck has the following complications and drawbacks:

- Decking is not engineered to carry sunroom loads, especially snow loads if you live in a snowy area.

- Most decks are not built to withstand the weight of a sunroom. The average weight of a sunroom is about 150 pounds per square foot, while the average deck is built to withstand 40 pounds per square foot. This means that adding a sunroom to your deck could cause it to collapse.

- Most decks are attached to the house with lag bolts, which are not strong enough to support a sunroom. The weight of the sunroom could cause the deck to pull away from the house.

- The flashing around the deck will not be able to prevent water from seeping into the house. This could lead to leaks and damage to the house.

- Decks are typically constructed as extensions of the house's interior. This may make enclosing a raised deck, without modifications to the house, quite challenging.

However, if you are convinced that a deck-top sunroom is the way to go for you, consulting a structural engineer is essential. If they confirm that your decking can indeed handle the weight, you are all set to go ahead with your sunroom project.

Remember, a deck sunroom, although practical, is never an off-the-shelf project and may involve substantial modifications to ensure the safety and quality of the end product.