When Matt was planning for his new deck, he wanted to make sure it was going to be very low maintenance and extremely durable. Who can blame him? Decks represent a significant upfront investment, but it’s easy to choose materials or make choices that mean ongoing maintenance and repairs.
After Matt chose thermally modified wood as his decking material (watch that research unfold in this video) it came time to choose a foundation option.
Anyone who researches deck foundations will quickly be faced with the ultimate question: helical piers or concrete piers? It’s obvious 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 for the pros, cons, and frequently asked questions about helical pies (screw piles) for decks.
What Are Screw Piles?
Screw piles, or helical piers, are a type of foundation system that’s been around since as far back as the 1800s which hints at how much of a lifespan these things have. They’re essentially giant galvanized steel shafts with screw-like flanges that are twisted into the ground. They’re twisted into the ground just deep enough that the torque required to turn it indicates a proper bearing capacity of the soil.
Usually, they’re installed to go just below to the frost line but sometimes can even go hundreds of feet deep depending on soil conditions.
These piers can be driven into most types of ground, but the solid rock does require some pre-drilling and also add to your cost. Stony soils are okay as well, but sometimes you might hit a large enough rock to have to start the process all over again and reposition the screw.
Advantages of Screw Piles
Screw piles are super fast to put in — 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.
Disadvantages of Screw Piles
While they’re easy to install, screw piles are not a DIY job. You need specialized machinery to install them.
How much do screw piles cost?
In Rise’s home of Eastern Canada — we’re paying on average $250 per standard helical pier. That price includes the full installation, brackets, and a nice little engineering report at the end so you know that the piers are rightly sized, rightly torqued, and will stay in the ground without shifting.
Screw piles vs. concrete piers
Now some of you may say that’s a hefty price to pay for a single pier, and you might be right. But consider this: by comparison, a concrete pier, which is another common pier, this time, where a hole is dug and concrete poured — is likely the most commonly used alternative for backyards and other pier applications.
Here are some more numbers to throw at you to consider if you’re installing these for a deck or large structure.
Material Cost Average: $70
Time to install: 2–3 days
Labor Cost: $30-$230 — and this will depend on machinery used and time to install which will vary depending on your soil conditions.
For those who say “I’m going to install these myself” keep in mind that a lot can go wrong with concrete pier installation. How much is your time worth to you? You’ll need lots of it for this job.
So at the end of the day, $250 doesn’t sound that bad now, does it? Especially for that piece of mind that your foundation won’t be going anywhere!
How might screw piles impact the environment?
Like everything else we do at Rise, we like to consider the planet impact of materials and products, so a couple of things to consider with helical piers:
Most of the embodied energy that goes into making helical piers is found in 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 plus though is that waste from this manufacturing process is still quite low and mostly from offcuts. That said, the overall embodied energy for helical piers is relatively low, and that’s also thanks to its installation process which is very straightforward.
How long do screw piles last?
Durability and longevity are also key to the helical pier’s low impact. They typically last a very long time and their durability usually depends on the quality of the pier as well as the soil in which it is placed.
How might screw piles impact your health?
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 potential contamination to the soil in which they are placed. This is also a good reason to pick a galvanized finish over a painted one.
What about DIY screw piles (helical piers)?
Here’s something I learned for smaller structures — so things like pergolas or even ground level decks might work with this option. I call these DIY helical piers. You can find them at most local hardware stores for about 25–30 bucks each (non-standard brackets are extra by the way) and they work essentially the same way as the helical piers we installed earlier, but with one big difference — you can install these yourself!
You’ll want to check your local building requirements and whether these helical piers are acceptable for your project.
Looking at these up close, they’re visibly smaller than the helical piers we had installed for the deck. The other big unknown here is whether we’re truly successful with our installation — by not knowing the actual torque required to turn the pier into place, we don’t actually know just how much weight these piers will support, which is why you may only want to consider these for smaller projects. Another thing I noticed with these smaller helical piers was the finish, which was powder coated, in comparison to the typical galvanized steel finish that is found with piers, and that does have longevity advantages over paint.
How to successfully install screw piles
You’ll want to get a helical pier contractor involved early in the process — sizing the right pier shafts can have a big impact on your project costs, and so knowing where you’ll place the piers and how many will be needed is essential.
In a perfect world, 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 a scenario where 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 — or else you might have to buy a brand new bracket to help support what you’re building
Double-check with your local building department is a good idea too, to make sure you’re meeting all code requirements. Usually, a sign of a good helical pier contractor is one who will provide an engineering stamp with the work, which you may need to bring to your local building department for sign-off.
Lastly, make sure you’ve prepared ahead by calling in before you dig for potential underground wires or pipes — your helical pier contractor may ask you to do that ahead of install. But aside from electrical or gas lines, be aware of anything else that may be hiding underground. I caught an issue at the very last minute with our yard where we had a drain tile exit in the exact spot of one of the piers. It was an easy fix to reposition the pier and something that could have caused some extensive damage.
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