From time to time I get asked whether or not our screw piles have sleeves / sheaths to protect the pile from ground movement. My answer is, “thankfully, NO!”
Consumers like the sound of a sleeve which floats up and down a pile with the freeze and thaw cycle. I must admit that at first, I thought “oh man, that makes a lot of sense.” However, once I looked into it further, I began to realize that the screw pile sleeve is only good in theory and for marketing.
- Screw Pile Sleeves Go Up But Don’t Come Down – When the freeze happens the ground heaves and the sleeve does as it should and it moves up with the ground. When the sleeve moves up it exposes the section of pile below which was previously covered by the sleeve and the ground then settles and compacts around the pile. Now when the thaw happens the ground settles once again, the sleeve can’t move back down due to the soil which now consumes the real estate it once covered.
- Screw Pile Sleeves Trap Moisture – Any moisture between the screw pile’s shaft and the sleeve gets trapped. Because the sleeves are typically non-porous there is no where for the moisture to go. If the screw pile is not galvanized or at least painted, the moisture will eat at the pile and will greatly accelerate the corrosion of the steel.
- Screw Pile Sleeves Are Redundant on Properly Installed Galvanized Piles – If your screw piling contractor chose a pile long enough to guarantee it it was anchored below the frost line (a minimum of 9′ pile in Winnipeg to ensure you are below our up to 8′ frost line) then the anchor of the pile would provide much more bearing capacity than the friction between the soil and the small (usually 1.5″ to 3.5″) shaft. Additionally, if the screw pile has been hot-dip galvanized, frost cannot adhere to the galvanization and friction is minimized even further.
Are you like me? You have to see it to believe it? Well check out this screw pile which was removed and replaced due to compromised integrity caused by a screw pile sleeve.
Now imagine you’re a customer with a screw pile foundation where sleeves were used – do you want to be out there every year trying to push your sleeve back into place or trimming it several inches every year? What if you were a contractor or home builder and your customers all started calling because the screw pile sleeves were creeping up on their structures?
Sometimes it’s better to be without!
For a professional grade 10 foot screw pile which is hot-dip galvanized and insulated, please contact Postech Winnipeg at 793-0653 and ask about Thermal Piles or visit www.manitobascrewpiles.ca.