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How To Build Concrete Patios

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Concrete patios are durable and, with some landscaping imagination, can complement garden, entrance or other landscaping. Some prefer this material as a base for bricks, but if designed creatively, concrete patios can be attractive in their own right. Although there's hard work involved, this is a suitable project for beginners to tackle.
Difficulty: Hard
Time Required: 3 days

Here's How:

  1. Building concrete patios requires some planning. Buy materials and tools ahead of time, and rent automatic cement mixer. Concrete calculator: to cover 50 sq. ft., 6 in. thick, you need 25 bags (pre-mixed, to expedite the project).
  2. Excavate with a garden shovel. In the North, 6 in. Two of these inches are for a bottom layer of gravel and the other four for the concrete. The gravel layer is meant to prevent your concrete patio from cracking during the freezing-thawing cycle. Make sure you establish a grade that slopes away from the house, for runoff. You can determine the grade by inserting stakes at the high end (up against the house) and low end of the excavation, then hanging a string between them. A line level placed on the string will indicate the present grade. Excavate so as to end up with a slope of about 1 in. for every 4 ft.
  3. Build a form to hold the gravel and concrete. Sink form into the area excavated for the concrete patio. The top of the form should be level with the ground, if you want the concrete patio to be flush with ground level.
  4. Install gravel, tamping it down firmly. Install 2 in.-high flat pieces of rock (rid your garden of some rocks!) as supports for rebar reinforcing, which you must build approximately in the middle of the 4 inch-thick concrete slab.
  5. Install reinforcing rebar to unify the slab. Make a grid by placing them at every two feet both from front to back and from left to right of concrete patio. Unite them with wiring at intersections.
  6. Mix concrete in rental automatic cement mixer, first adding water with a garden hose to the mixer, then concrete, then water again -- until mix becomes a uniform, shiny medium gray.
  7. Pour concrete, starting at end farthest from where your mixer is, building a ramp if necessary. Add filler rocks as you go. Pour as fast as possible. Preparation is crucial here.
  8. Use a screed to level the surface of the concrete, sliding the screed along the top of the form boards. Pull the screed from one end to the other, drawing off excess concrete.
  9. Cut initial control joints in concrete patio at about every 3-4 feet with a mason's trowel (not a garden trowel), 2 in. deep. To achieve a straight cut, place a board across your forms at right angles to use as a guide.
  10. Look for a watery layer to appear on the surface of your concrete (which is said to "bleed" as it settles). After this watery layer appears, wait for it to disappear before proceeding.
  11. Use a float to even out any lumps on the concrete patio. Sweep it in an arc-shaped motion, keeping the edge at the front of your sweep slightly raised, lest the float dig into the concrete.
  12. Finish the control joints begun in Step 9. Use a jointer to make a clean groove, about 1 in. deep (or 1/4 the depth of the total slab). Re-use the same board as a guide.
  13. Finish the concrete patio surface with design elements. Running a pushbroom over the concrete patio makes a design both attractive and practical: lines that provide visual interest and a slip-resistant surface.
  14. Lay plastic over the new concrete patio. Concrete must be "cured" properly. The key to curing is not letting it dry out too fast. By laying plastic over the concrete patio, you trap the moisture within. Keep the plastic on for a week. Concrete doesn't fully cure for 3 weeks, so even after you've removed the plastic, don't subject the concrete to undue stress. In terms of sealing, wait time varies by product (follow the instructions supplied for your product).
  15. If you anticipate that there will be a large amount of water runoff from your patio and that this runoff will cause problems, you may want to look into having a drainage system installed in your yard prior to building a concrete patio. Once such an overall drainage system is in place, you can focus on drainage for your concrete patio. There are drains meant especially for patios, called "linear drains," and these drains tie into the overall drainage system for your yard.

Tips:

  1. Avoid skin contact with concrete, as well as inhaling the dust. Make use of gloves, kneeling boards, long pants, long-sleeved shirts, protective boots, goggles, face masks, etc.
  2. In my area, Home Depot rental has a 24-hr. rate for automatic cement mixers that is cheaper than the 10-hr. rate of smaller rental service stores. When in doubt, buy extra concrete. You don't want to find out that you're a bag short just as you're about to put the finishing touches on your masterpiece and the concrete is starting to harden!
  3. If you want to lay bricks on the concrete slab and end up with the tops of the bricks flush with the ground, dig an extra 2 1/2 in.-- 2 in. for the bricks and 1/2 in. for the mortar between the bricks and concrete.
  4. If, in your digging, you come across any stones, wash them and set them aside to be incorporated into the concrete. They'll take up space and save on concrete usage. It's also a good time to dispose of garden rocks.
  5. If you're digging 6 in., 2x6s make an ideal form. But since their tops will be flush with the ground, prevent debris from falling in on your project by covering the landscaping area with tarps.

What You Need

  • "pre-mixed" concrete
  • automatic cement mixer
  • gravel, screed, float
  • four 2x6s, scrap boards
  • nails, garden shovel
  • rebar, wire
  • garden hose
  • trowel, jointer
  • protective clothing, mask and goggles
  • line level
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