Resurrecting fallen walkway pavers
By Tom Phelan - ReminderNews
Feature Article - posted Wed., Aug. 17, 2011
If you have ever trod the historic brick sidewalks of Boston's Beacon Hill, you will know what treachery can be wrought by sunken and raised paving stones. If the steep pitch of the Hill doesn't cause you to stumble and fall, the consistently erratic levels of the bricks will trip you up more than once on the way up and down.
If you installed your own stone-paved walkway, you are intimately familiar with the painstaking process required to install a well-set decorative, though functional path. Yet if you did install your own path, and don't recognize the "painstaking" part of the project, your stones may have already erupted. Whatever the cause, the repair is not difficult.
First, identify the area that needs repair. Hopefully the problem areas are few, and each depression is limited to a few blocks. Use a long level or even a 4-foot length of 2x4 set across the depressed area. Move the straightedge around a few times to be sure you identify all the stones that need to be raised. Mark the stones that no longer touch the bottom of the board or level. Mark your ailing pavers with a washable marker or just sprinkle them with a little flour.
Removing the first depressed brick or paver stone will take some time. Once the first one is out, the others should be easier to remove. You can use a straightedge screwdriver for the extraction, or fashion your own tool from a sturdy length of steel wire - a coat hanger should be rigid enough. From a straight length of wire, create an L-shaped tool. The bottom only needs to be about 1 inch long. Make a longer L in the opposite direction to use as a handle.
Work the screwdriver into the sand between adjoining pavers, and apply a prying motion while you jar the surrounding stones with a mallet or length of 2x4. The paver should begin to work its way up out of the walk. Alternate the process on opposite ends of the paver. If you make the L-shaped extraction tool, work the shorter side down into the sand, and rotate it 45 degrees, such that it hooks under the paver. Then pull upward while you hammer on the surrounding stones.
If your stone pavement was installed correctly, the pavers will be supported by a couple of inches of stone dust or concrete sand over a bed of 3 to 5 inches of ¾” process stone. That bedding should have been well-tamped and leveled, and inclined where appropriate. Metal or hard plastic edge constraints around the circumference of the pavement hold the stones in place.
Once you have removed all the stones from the reconstruction area, you will need to spread a new layer of sand, and level it to receive the stones once again. The level of the sand must be slightly high, because it will be compressed during the reinstallation process. To level the sand, cut a screed board with notches at each end. The notched ends will rest on the stable pavers. The depth of the center of the screed should be about 1/8” less than the thickness of the paver. Fill in the low areas, level with the screed board, tamp, and repeat until you feel you have a level, firm base.
Replace your stones on the repaired sand base. Cover the area with sand, and work it into the joints between the stones. Tamp the stones and repeat the process until the stones are snug and the spaces between them are well filled.
As you are going through the repair process, look for signs that can help you understand why the stones lost their level. The prime suspect should be faulty installation technique - not building enough solid base or perhaps a base that used too much sand and not enough process stone. Inadequate preparation will inevitably cause failure in any DIY project over time.
Water flowing across the walk, maybe from a gutter drainpipe or other run-off, can easily erode the layer of sand below the stones. You may have repeatedly piled up snow on certain sections of the path that at some point turned to ice, and worked on the stone construction below it.
Another possible culprit for the stone-paved walkway might be moles or voles that have tunneled under the walk. Weight on the walkway would compress the critter's network of tunnels, and the stones could sink.
Whatever the reason, find it, and eliminate it as a cause of future stone-paved walkway failure.