When the exterior slabs in our home were poured, they used redwood spacers — and left them there for effect (and a nice control joint)... which is nice until they degrade. Most folks tear the wood out and replace with gravel or other hardscape material and we had done the same. However, years of sweeping pea gravel out of the atrium became tedious.
I've wanted to replace the redwood for years and this weekend we did. I wish we had done it years ago. It's pretty simple:
- Rip out the old redwood
- File down the original nails
- Cut new strips to size
- Using construction adhesive, re-set the redwood strips and let dry
- Fill in gaps with (polymeric) sand
When you remove the redwood, the remnants of the securing nails will remain — be careful... they're sharp and rusty. When originally poured, the contractors simply hammered in nails every foot or so (heads sticking out) and when the concrete was poured around the strips, it sealed it up tightly. However, with the wood gone, the nails remain and you'll need to use a grinder or Dremmel-tool to get them out.
After that, you'll need to measure and make some test blocks... some joints have probably opened up more than others. You will probably be looking at 1.5in square — which means you can get two out of a 2X4. Don't make the new strips too tight as they'll expand when wet.
If you have giant cracks in the slab (which is what the control joints are for) and insecticide is your thing, it would be a good time to pour insecticide in the joints to treat for ants or termites before you seal everything up. We use Bifenthrin and Fipronil for ant/termite control and purchase through eBay suppliers.
Clean up the channel with a wire brush and set the strips in a bead of construction adhesive. I like the kind with polyurethane adhesive added (aka: Gorilla Glue) as it "foams" a bit. You could also simply use Gorilla Glue, but you'd want to be careful as it could foam too much.
Use shims to space everything out nicely side-to-side and if an area pops up, use the friction of the shims to hold the strip in place.
When finished, sweep polymeric sand (or regular sand if you'd like) into the joints. The "juice" in the polymeric sand darkened the redwood a bit which is kind of nice as it was fairly pink otherwise. It should fade to a silvery-gray over time.
Next up: the driveway!