shifting posts

k92thdr@hotmail.com · 06-06-2009, 08:30 AM

Hi,
We have a boathouse built on the shoreline and back. We have had a problem with shifting posts and unsupported areas of the boathouse or raised areas in the winter related to the frost in the ground. The doors don't work in the winter because of this. We have had a structural engineer have a look at it and have spent a lot of dollars re-pouring foundations- all to no avail.
My question is are there such a thing as self levelling posts? Maybe ones that have a computer chip in them to tell if they are out of level and then self level? The posts are exposed to extreme temperatures- minus 40 C in the winter and up to plus 30 in the summer.
If someone could give me some help on this I would appreciate it.
Colleen
k92thdr@hotmail.com

GBR · 06-06-2009, 09:02 PM

The reason posts heave or jack, is because water freezes around the pier in and under the concrete pier. Yours is a special situation with the water table so close. Here is a very good article on heaving posts: Building a deck: expert advice from ... - Google Book Search

To stop frost heave, normally, gravel is placed under a footing base, and in the back-fill hole to keep the water from freezing and forming "ice lenses". Google that, and frost jacking, frost heaving, etc. Notice they wrap plastic around the sonotube to prevent the freeze from pushing the pier up. And yet:

How Aggregates Prevent Frost Heave Be safe, G