If you are considering building a deck for your next home remodel project you have likely considered location and aesthetics. From here a deck builder or architect will generally come up with a drawing and a plan on how to build. You may be included in the decision making of colors and styles for the finish products but the builder will decide on the structural components and technical build procedures.
One could dedicate an entire website or blog to deck building but I will try to cover three general topics on technical aspects of deck building in a short series. When i approach a deck build from a builders perspective there are three main categories to consider; Footings, Decking and Railing System. Under footings there are things to consider such as weight, soil conditions and depth. In the decking and railing categories you consider not only quality, cost, maintenance and appearance but the layout and how it will manipulate the framing.
Footings are the most critical structural component of a deck or addition and state and local guidelines should not be taken lightly or forgone especially in climate zones like Minnesota. The negative impacts of a poorly installed or designed footing can drastically decrease the lifespan of your investment. The reason frost depth is considered in footing design is to mitigate heaving and movement due to the freeze thaw cycle. When the depth of the footing is below the depth of the freeze or frost, the ground the footing is bearing on is less likely to move which in turn pushes or pulls on the framing components of your deck causing sagging or warping of your decking and railing components. It is the root of a lot deck issues.
Sizing and depth charts can be found in Minnesota code books and on local government sites and can vary based on soil testing in specific localities and the weight of the bearing structure. If you have loose or wet soil or if your deck will be supporting a hot tub the quantity, spacing and size will be subject to change. This is not an article on the specifics of sizing and spacing but to provide general understanding of the purpose of footings so you can make sure to make informed decisions. These sizing charts are a guideline for a generic standard and if you have a unique project you may want to protect it by getting a second opinion on the footing design from and engineer.
Footings have evolved over the years as issues have been found and engineering and standards have expanded. What started as a hole in the ground with a buried post has changed to a hole in the ground with post resting on a concrete pad and buried which changed to a hole in the ground filled to finished grade with concrete and a post bearing on top. From there sizing was adjusted based on weight and with soil testing came more changes. In recent years uplift mitigation was improved by adding a "bell" shape to the bottom of the footing and footings began to get poured above grade to prevent water from collecting, freezing and cracking the concrete. Probably the most significant changes is the introduction of a completely new footing design called the Diamond Pier Footing.
The Diamond Pier footing is revolutionary because of its ability to be installed in minutes whereas the classic footing consisted of digging a hole, having it inspected, pouring concrete and letting is cure and finally mounting the hardware to connect to the post. This results in a major labor cost savings. The design and technical information can be found here. https://www.diamondpiers.com/ From my own experience, since this is a relatively new product that drastically differs from the classic footing it is taking time for it to be recognized by local governments until data is gathered over long term use and in different environments. There are cautions about loose and rocky soils as of now but I am sure as the engineering continues the product will adapt.
To conclude this rant I want to make it known that I am by no means an engineer of any sort but a residential contractor who has seen good installs as well as bad and have done a fair share of research of my own accord and through schooling. I hope to inform the average homeowner that this part of deck building is not something to take lightly and that there are many things to take into consideration. If you happen to be looking for a remodel contractor to take you through your deck building process check out our page below.