Ensuring Stability with Deck Footing Piers
Often here in our blog articles, we look at different products, systems, and methodologies used in modern deck Construction to build decks better. Our company builds some of the best decks in the world. We are very specifically intent on driving the quality in the industry so that as an industry leader, we set the standard higher for the entirety of the builders in the Washington DC metropolitan area. Today, we’re going to look at some examples of really bad deck construction.
We’ve had a few different blog articles like this, here on our website. Each of these blog articles is focused on different areas and different elements of deck construction. Today, we’re specifically going to look at a deck built on a hillside that has a very steep slope. We don’t want to make it sound like this type of work is easy and it could have just easily been done better without any extra effort. It is plainly very complicated and expensive to build at a high slope hillside.
However, some sites and some properties are more challenging than others and there’s almost always a solution or two that can be applied to make things much better. Most of these better or best practices have an additional cost, but we simply argue, its worth it. There are lots of reasons why.
People can learn a lot from their own mistakes, but it’s even smarter to proactively learn from other people’s mistakes and build better.
There’s a list of problems, defects, shortcomings, and issues with the installation shown in the picture below. We’re looking at a picture of two deck posts set on top of rectilinear footings that extend above grade and also presumably go to a relatively deep depth below grade.
These footings are buikt from cast in place concrete, built with formwork. Essentially a formwork is a box built around the area of the footing and as the concrete is poured into the footing, it takes the shape of form work. Later, after the original construction of the footings, the formwork can be stripped away. Formwork doesn’t always have to be stripped away, but it generally makes sense because concrete is a durable material that can resist exposure to exterior elements and in most cases formwork itself cannot. Also, from a practical perspective, formwork can generally be reused for future work or for additional elements of the same project.
Footings like this are often used to encase the wooden post. The in case you were talking about here though is different than the concrete. Instead, we’re talking about a permanent installation where the wood is set inside of the concrete. We generally recommend against encasing wooden posts in concrete, particularly where the concrete and the post extend below grade, in most cases. It’s not cut and dry, and both methodologies have some unique advantages.
One of the most direct and obvious advantages to encasing a wooden Post in a concrete footing is that the concrete footing stabilizes the positioning of the wooden post. Nonetheless though, the problems caused by encasing the post generally outweigh the advantages and other methodologies such as secured base plates can provide the same or similar positioning security without the risk of accelerated deterioration.
The building code doesn’t seem to be cut and dry or clear enough on this and they seem to allow treated posts to be embedded in concrete, even in below grade circumstances, where the post is simply preservative treated. However, this is a bit risky because there are several different types of preservative treatments that can be applied to wood and these different types of treatments can have significantly varying effects or abilities to actually preserve the wood.
Concrete footings seem to encase embedded elements in a waterproof or watertight enclosure, but that’s not actually accurate. Concrete is actually permeable. It’s a common misconception that even fools some builders to think concrete is completely or significantly waterproof. Concrete is definetly a strong and tough material, but concrete is actually permeable to a degree.
Concrete generally includes a degree of pores, which in effect are tiny voids within the concrete structure. These pores are a natural result of the mixing and hydration process of cement, water, and aggregates. These pores can be interconnected, allowing liquids and gases to pass into and through the concrete. Even where it appears that isolated pockets of air, left in the concrete, are separate, they can be interconnected through microscopic or even hairline size cracking that naturally occurs in concrete.
This type of hairline cracking is extremely common and could effectively be considered a natural result of the concrete casting and curing process. Although these cracks can be microscopically small, they can still allow water to pass through and enter into voids or pocket areas, where those voids are pockets are interconnected, water will continue to flow and or enter and where they’re separated, hairline and or very small cracks will often allow bridging or interconnectivity between these small voids in pockets.
At a glance, the staggered joists make the deck look like it was put together using a pile of scrap wood, using whatever length of board was available from the pile. Of course it doesn’t look professional, but even more importantly, a rim joist which essentially ties all of the joist ends together is missing. Fasteners have been used, but structural ties have been omitted where the joist ties to the girder in this case is the horizontal board which spans from post to post, providing a bearing point for each of the individual joists as they project away from the higher area of ground.
As well, another important detail, which is easily missed, is that there is no shouldering between the girder and the substrate post. In most cases, a notch should be cut into each of the posts so that the girder can rest in a shouldered rabbet.
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
