Last Updated: May 31, 2021
When Rise's CEO and Founder, Matt Daigle, was planning for his new deck, he wanted to make sure it would be low maintenance and extremely durable. Who can blame him? Decks represent a significant upfront investment. If we don't pay attention, it's easy to choose materials or make choices that will mean ongoing maintenance and frequent repairs.
After Matt chose thermally modified wood as his decking material (watch that research unfold in this video), it was time to select a foundation option.
Anyone who researches deck foundations will quickly face the ultimate question: helical piers or concrete piers? It's evident by the title of this article what Matt chose. So, to save you the Googling, we'll lay out the results of his research here. Keep reading, and we'll take a look at the pros, cons, and frequently asked questions about helical piers (also known as screw piles) for decks.
Screw piles, or helical piers, are a type of foundation system. This method of supporting a structure has been around since the 1800s - which hints at their long lifespan. They're essentially giant galvanized steel shafts with screw-like flanges. To install screw piles, they are twisted into the ground to a depth that the torque required to turn them indicates proper soil bearing capacity.
Usually, installation extends to just below the frost line. They can sometimes even extend to hundreds of feet down, depending on soil conditions.
These piers can be driven into most types of ground. However, if solid bedrock is encountered, it requires some pre-drilling, which will add to your cost. Stony soils are okay, but sometimes you might hit a large enough rock to have to start the process all over again and reposition the screw.
Screw piles are quick to install — it's kind of like an instant foundation. They work in a variety of soil conditions, and the installation is pretty cost-effective. Screw piles have relatively low embodied energy and are relatively non-intrusive in the surrounding environment.
While they're easy to install, screw piles are not a DIY job. You need specialized machinery to install them.
On average, screw piles (helical pier) cost $250 per standard screw pile That price includes the full installation, brackets, and a helpful little engineering report at the end. This professional installation gives you the peace of mind, knowing that the piers are appropriately sized, correctly torqued, and will stay in the ground without shifting.
Now some of you may say that's a hefty price to pay for a single pier, and you might be right. But consider concrete piers for comparison. These are another common pier wherein a hole is dug, and concrete poured. Concrete piers are likely the most commonly used alternative for backyards and other pier applications.
When installing concrete piers, your material cost will run about $70, and the install time will be between two and three days. The cost to install is wide-ranging - between $30 and $230, depending on the machinery you will need, based on your soil conditions.
When considering a DIY installation, keep in mind that a lot can go wrong with concrete pier pouring. And how much is your time worth to you? You'll need lots of it for this job. So, in the end, $250 might be a reasonable price to pay. With it, you will have the comfort of knowing that your foundation won't be going anywhere!
Most of the embodied energy that goes into making helical piers stems from the harvesting and manufacturing process, and a bit in transportation. They're typically made from steel and coated with zinc and require sources of high heat. One advantage is that waste from this manufacturing process is quite low and mostly from offcuts. That said, the overall embodied energy for helical piers is relatively small.
Durability and longevity are also critical to the helical pier's low impact. These products typically last a very long time. Their durability is, of course, dependent on the quality of the pier and the soil in which it is placed.
Steel piers have very little to no impact on their surroundings from a health perspective. Typically we'd look at any potential off-gassing from the material or any possible soil contamination in their vicinity. Soil health is also an excellent reason to pick a galvanized finish over a painted one.
For smaller structures, like pergolas or even ground-level decks, DIY helical piers might work. You can find them at most local hardware stores for about $25 to $30 (non-standard brackets are extra). They work the same way as the helical piers we installed earlier, but with one big difference — you can do it yourself!
These are visibly smaller than the helical piers Matt installed for his deck. The biggest potential issue with these smaller options is knowing whether their installation is successful. Since you can't measure the actual torque required to turn the pier into place, you won't be able to tell just how much weight these piers will support. For this reason, you may only want to consider these for smaller projects. Also, these smaller helical piers usually have a powder-coated finish instead of the more durable galvanized steel finish.
It is best to get a helical pier contractor involved early in the process. They can advise you on sizing the suitable pier shafts and location selection and know how many you will need.
Getting a geotechnical survey done before committing to helical piers is ideal. That said, you may be able to skip this step for smaller projects like a deck build or when a pier contractor is familiar with the area's soil conditions.
Make sure that the brackets supplied with the helical piers are compatible with your project. Otherwise, you might have to buy a brand new bracket to help support your structure.
Double-checking with your local building department is always a good idea too. This way, you can ensure that you're meeting all code requirements.
Usually, a sign of an appropriate helical pier contractor will provide an engineering stamp with the work. You may need this for approval from your local building department.
Make sure you've prepared ahead by checking for potential underground wires or pipes before you dig. Your helical pier contractor may do this, or they may ask you to do it ahead of install. Aside from electrical and gas lines, be aware of anything else that may be hiding underground. Matt caught an issue at the very last minute in his yard - they found that a drain tile exit was in the exact location of one of the piers. It was an easy fix to reposition the pile, and it could have caused extensive damage had it not been discovered ahead of time.
Now that you know all about helical piers, please don't forget to leave your comments on the video! Thanks again for checking this out, and we'll catch you on the next one!
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