Here in the midwest, we sometimes get several freeze/thaw cycles each winter. As we all know, this is the root cause of frost heave. The more cycles the greater the heave. My question is this. When designing a raised benchwork type RR, do all the supports need to be either buried below frost line, or all set on blocks set on gravel bases? Can the supports be mixed or is that going to create a lot of problems?
Ben H.
I would think a mix would cause problems(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)
The frost here in Eastern Ontario is as great or worse than where you are Ben. We stopped using anything that goes into the ground years ago. We only use deck blocks set either on a patio stone, or in some cases just the leg of the benchwork on the patio stone, if the location is relatively dry. Whatever you do, just don’t disturb the soil anymore than you can help, if it is already fully compressed. Let everything float.
Since I based a lot of what method I would use on what I saw up at Fred’s the deck blocks I left directly on the ground.
The cap blocks I did sink in the ground for lateral stability and to keep it somewhat level.
Of course, this hasn’t gone through one of our winters here yet, but I don’t for see any serious problems. Then again if you check back in the spring, I may sing a different tune…(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
I would imagine that your frost line is between 30 and 50 inches. For zoning purposes, ours here in Western CT is 40". If you are going to dig every post that deep and set in concrete it would certainly be stable, but that’s about 500% more work than I would want to do and makes removing or relocating track very difficult.
I think Fred’s method that many have followed makes more sense. I think it works because the weight of the bench work minimizes any heave and helps push things down when the thaw comes. I don’t have any elevated sections directly on dirt so I can’t add any practical experience.
My main yard is built on a bench similar to the construction Ken pictured. It has been in place for 2 winters now with no issues but then again our winters on Cape Cod are usually mild.
Save yourself a ton of work and go with the cement footings. If frost does push one up you can slip a shovel underneath to remove some of that heaved dirt. Try not to disturb the ground too much when building.
Happy RRing
