One of the constant background projects we have is extending the concrete driveway toward the house. We try to keep roughly sixty feet of forms set up at any given time so when the opportunity comes up we can extend it. Forming a driveway is about as simple as it gets, but it takes a little practice.
The first thing we did was stretch a string line down the North side of the driveway. One stake was driven at the top, and another down the hill with a string stretched tightly between them. This provides a visual reference for keeping the side of the driveway straight. Then another metal stake is driven so that the center of the board will line up with the string, and a 2×4 is nailed to the stake at the desired height. Each 20 ft. board has three or four stakes to support it, and to connect two together you just hold the ends together and toenail them.
Once one side is straight, we take a spacer board whose length is the desired width of the driveway, and stake and attach the boards on the opposing side in the same way, making sure that the distance between them matches the length of the spacer board.
The distance of driveway poured is determined by the amount of concrete as well as the thickness of the slab (the higher the form boards are raised, the thicker the driveway will be). The spacer board becomes a floating end which is dropped in where the concrete runs out.
Doug has a magnesium screed board that is rested on top of the forms and dragged along to create a level surface. Having the right amount of concrete is a bit of an art, as trying to drag too much wet concrete with the screed board will wear you out quickly.
Once the surface is relatively flat, a bull float is run over the surface to smooth it out. This also reduces the surface area of the driveway, which will slow down the drying time and give you a bit more time to work with it. When it is still a little wet, we run an edging tool around the top of the forms to soften the top edges of the driveway, and cut joints every 10 or so feet with a handheld jointer. The joints give the driveway a natural surface to crack as it cures and shrinks, in order to prevent ‘unplanned’ cracks in the surface.
The final step is to broom the surface with a large flat broom head. This adds some texture to the surface to keep it from being too slippery. Once the concrete sets up (generally by the next day) you strip the forms, pull the stakes, and extend the string line if needed and set everything up again at the end of the slab.
The degree of difficulty is influenced quite a bit by the consistency of the concrete, and concrete that is too dry can be really hard to move around.
So far we have done about 150 feet with several hundred to go. Here are some pics of what we have so far.
