Essential Guide to Diagonal Deck Bracing: Part I
When building decks, you need to think about several load path and uplift factors required to make the structural framework strong and stable. This means thinking carefully about what forces will affect the deck, the sizing of each element and its material (or grain and species composition), and how it’s configured. Today’s article looks at the structural construction of the deck frame and structure, aspects of deck bracing, considering the structural connections, characteristics, and resistive forces of these elements.
When designing and building decks, you need to think about all the different forces that will act on them. These forces fall into three main categories: static loads, dynamic loads, and environmental factors.
Static loads are the weights that don’t move or change much over time. Think of them as the constant pressures on the deck. There are two main types of static loads. First, we have the dead load. This is simply the weight of the deck itself – all the wood, nails, screws, and other materials that make up the structure. It’s called “dead” because it doesn’t change; once the deck is built, this weight stays the same. The second type of static load is the live load. This includes the weight of people, furniture, grills, and anything else that might be on the deck. We call it “live” because it can change – sometimes there might be just one person on the deck, other times there might be a big party with lots of people.
Although the live load is technically classified as a static he can act a bit like a dynamic load, depending on how it’s being used, especially under the weight of people standing on the deck. There’s been some interesting videos on social media and stuff like that that show people overcrowding and jumping up and down on top of decks which calls them fail under the weight, but it’s not just the way itself that’s causing the failure, it’s also the fact that this static load is also acting a bit more like a dynamic load.
Dynamic loads are forces that change quickly or suddenly. These are the kinds of forces that can really stress a deck structure. Wind is a big one in some places like tornado alley, and also not quite as much of a concern can be a factor here too. When strong gusts hit a deck, especially if it has a roof or privacy screens, it can push the structure sideways. This is why we need to think about bracing to resist these lateral forces. Another dynamic load is seismic activity – in other words, earthquakes. In areas prone to earthquakes, we need to design decks that can flex and move without breaking or collapsing.
Environmental factors are the third category, and these can be tricky because they often combine aspects of both static and dynamic loads. Snow is a good example. When snow piles up on a deck, it acts like a static load – it’s just weight pressing down. But it’s not constant like the deck’s own weight; it can change as snow falls or melts, and it might not be evenly distributed. This is why decks in snowy areas need to be extra strong. Another environmental factor is temperature change. As materials heat up, they expand, and as they cool down, they contract. This constant expansion and contraction can stress the connections in a deck over time.
Understanding these different types of loads is crucial for building safe, sturdy decks. We need to calculate the maximum possible load in each category and design the deck to handle all of them combined. This means choosing the right materials, using proper connection methods, and incorporating appropriate bracing techniques.
For example, to handle static loads, we might focus on the size and spacing of joists and beams. For dynamic loads like wind, we might add diagonal bracing to resist lateral forces. And for environmental factors like snow, we might increase the overall strength of the structure and ensure good drainage to prevent snow buildup.
Remember, in the real world, all these forces act together. A deck might be supporting the weight of party guests (live load) while also being buffeted by strong winds (dynamic load) and bearing the weight of recent snowfall (environmental factor). A recap follows.
- Static Loads:
- Dead Load (DL): Weight of the deck structure itself
- Live Load (LL): Occupancy and furniture weight
2. Dynamic Loads:
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- Wind Load (W): Lateral forces from wind pressure
- Seismic Load (E): Ground motion forces
3. Environmental Factors:
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- Snow Load (S): Accumulated snow weight
- Thermal Expansion/Contraction (T): Stress from temperature changes
This coming week, we will talk about the load path of the structural connectivity between the various elements of a deck, working through a vertical chain that connects the elements from the walking surface of the deck down all the way through to the footing underground. We’ll also look at the calculations related to the impact of wind and the exterior elements of nature.
Use a contractor who understands and cares about doing things right. Always, feel free to reach out to us here at Dupont Decks and Patios. We are happy to help with almost all steps of the deck building and design process. Let us know about your ideas and talk to us if you have questions about possibilities . You can call us at (202) 774-9128. You can find us online at https://dupontdeckspatiosdc.com and you can email us there as well at https://dupontdeckspatiosdc.com/contact-us
