A lot of time spent thinking about sidewalks

Posted Feb. 12, 2010, at 6:20 p.m.
Last modified Jan. 30, 2011, at 11:28 a.m.

I spend a lot of time thinking about sidewalks this time of year. That is because my sidewalk goes on a little trip up in the air a bit from frost heaving.

When we bought this house, there was a walk that was done with 24-inch-square pavers. They were bedded in sand, and during the first two winters the walk was relatively flat. It did not seem to move when the ground froze.

A couple of years ago, we took the pavers up and extended the walk and installed new pavers. The next winter, the sidewalk moved up when the frost came and then back down once the frost went out.

It has done this for several years now.

This is an interesting study. The original pavers were white. The newer pavers are dark gray. I suspect that the difference in color had some effect on the emissivity of the paver. Emissivity is the ability of a surface to allow heat to radiate to a cold winter sky. In simple words, it sucks heat out of the ground and the ground underneath the pavers freezes. Once this happens, if water is present in the ground, the water expands as it freezes and the ground, and pavers, rise.

Since the “system” worked before we replaced the pavers, it seemed like a good idea at the time not to change anything.

I knew better, but I do like to take the path of least resistance. Pulling up the old pavers and installing new ones is a simple task. Flawed, but simple.

There are a couple of things that we can do to solve this problem.

We can put drainable material such as gravel underneath the walk, but have it on top of the existing soil to assist in draining water. The problem is that the native soil is heavy with clay. It holds water well, and simply draining the surface water will not necessarily solve the problem.

Since we want to do this only once, it is wise to install a layer of foam insulation on the ground before putting down some gravel and sand.

You might have noticed that roads like the interstate never have frost problems the way older secondary roads do. This is because the roads are well-drained and are up in the air a bit compared to the adjacent grading. It is a good idea to do this with walkways and driveways if possible. We want water to run off the areas that we have to drive or walk on. The insulation underneath is insurance against frost movement.

While we are thinking about the frost heaving, we can consider one other addition to this project. If we are installing insulation and then bedding it in sand or gravel, we can install some snow-melting tubing under the pavers.

Since I am spending a lot of time thinking about sidewalks, there is another option that I like. There are several locations in the town where I live that have boardwalks instead of pavers or more conventional walkways. I like the idea of boardwalks. There is minimal surface preparation, although they should be somewhat level.

Because of the way they are built, they are self-draining. They might allow a savvy carpenter to install a snowmelt system.

And you get to work with wood, preferably pressure-treated, which might be simpler than fooling with pavers.

I guess it is a matter of what you like to do and what your sense of aesthetics is.

Since the heaves are not that great, and the pavers might drop back into place come spring, I might just have to study this a bit longer.

Questions for Tom Gocze should be mailed to The Home Page, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. A library of reference material and a home-project blog are at www.bangordailynews.com/thehomepage.html.

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