A patio is a wonderful detail for any home, but typically you need to weigh the benefits of this surface with the expenses involved in building it. To save a little, it is possible to include the pouring of the concrete among the "do it yourself" projects.
Steps
Part 1 of 4: Prepare the Zone
Step 1. Choose the surface on which you want to build the concrete patio and evaluate its dimensions precisely
Its length and width determine how much concrete to use and which model of concrete mixer to choose. If you plan to build a very large patio, it is probably a project that is beyond the abilities and possibilities of an amateur bricklayer. An equally important aspect is the location: you have to choose a mostly flat area so as not to be forced to level the ground before pouring the concrete.
- Go to the technical office of the Municipality and read the local building regulations, ask if a permit is necessary, if there are any provincial or regional regulations and evaluate the distances between the future patio, other properties and utility pipes.
- Before digging in the garden, find the exact location of the septic tank, underground facilities, or other pipeline.
Step 2. Plan out the posts at the corners of the patio area
Stretch some string between the posts and use a level to determine the slope. The stakes and twine give you a good idea of how the patio will match the garden; make the necessary changes if necessary.
- Sharpening the ends of the stakes makes it easier to push them into the ground.
- If the ground is uneven, you have two choices: increase the height on one side or dig into the other.
Step 3. Remove all weeds, grass, roots and top soil layer from the twine bounded area
You can proceed to this stage using a hoe, shovel, or other common gardening tools.
Part 2 of 4: Prepare the Base
Step 1. Decide if you want the patio to be flush with the ground or raised
In the first case, dig a hole as large as the entire patio, 20 cm deep; instead limit yourself to a depth of 10 cm if you opt for a raised surface.
- If necessary, compact the earth.
- If you plan to place something very heavy on the patio, such as a brick barbecue, the first thing to do is to build a foundation to ensure greater stability.
Step 2. Add a layer of gravel or crushed stone to the pressed soil
Typically, this type of base should be 10cm thick.
Make sure the crushed stone is evenly laid out and pressed well. Any fluctuations in its thickness can cause the concrete to crack or fail over time
Step 3. Drive stakes into the ground along the new patio perimeter, spacing them at least 60cm from each other
Make sure they are slightly out of the way of the twine you stretched earlier; you will need them in the final stages to support the outer edge of the screed.
- Make sure they are firmly planted in the ground.
- A slope must be provided to allow rainwater to drain. The standard one is 5 mm for each linear meter, but check the building specifications of your municipality to know the exact value.
- Do not underestimate the weight of wet concrete. Use very sturdy wood, otherwise it could bend and even break under the pressure of the material; to avoid this problem, consider using steel formwork.
Part 3 of 4: Install the Formwork
Step 1. Cut planks with a 5x10 cm section to create the structure needed to contain the concrete
Cut them so that the inside sides of the formwork are the same length as the patio dimensions. At the end of the laying of the surface, these elements are removed, so you do not have to take into account their thickness, otherwise the patio will be smaller than what you wanted.
Step 2. Line up the boards with the string you stretched to delimit the perimeter
When you insert the board into the ground, you need to make sure that it is exactly under the rope. Remember that the formwork acts as an exterior patio wall, so make sure it's in the right place.
Step 3. Nail the planks to the posts
The latter are the supports of the formwork to prevent it from bending under the weight of the wet concrete. Check that the planks, posts and nails are very sturdy; the latter must be long and strong enough.
- You can use screws instead, but in that case you also need a screwdriver.
- As you nail the planks to the posts, make sure they are level; use twine or a level to check this detail, otherwise you risk the patio being uneven.
Step 4. Saw off the protruding parts of the posts
Their ends should remain just below the edge of the formwork and not be visible above the concrete surface.
If you are pouring concrete near the house, another screed, or any structure, place an insulating joint between the existing surface and the fresh concrete. The joint allows the concrete to stabilize, minimizing the possibility of cracks forming; the insulating one is generally made with fibers impregnated with asphalt or compressible foam rubber that is applied to the wall or surface on which the new patio rests. You can find these couplings at most hardware and home improvement stores
Step 5. Coat the inside of the formwork with vegetable oil or a commercial release agent
This way, you make sure that the concrete does not stick to the boards, which you can then remove when finished.
Part 4 of 4: Casting the Concrete
Step 1. Mix the concrete
You can do this by hand or with a concrete mixer, but always respect the instructions you find on the material bags. These report the doses of water and the duration of mixing.
- You can define the number of cement bags you will need by calculating the cubic meters occupied by the screed. Multiply the thickness by the length and width of the casting to find this value; alternatively, you can use an online calculator.
- If you have decided to mix by hand, pour the concrete into a wheelbarrow or concrete tub; work the mixture with a shovel or a hoe without forgetting to wear gloves and safety glasses to protect yourself.
- If you have opted for the concrete mixer, make sure it is near the site where you have decided to build the patio; put it in the correct place before starting work.
- Whether you can mix the concrete by hand or whether you need to use a concrete mixer depends on the amount of concrete.
Step 2. Cast the concrete
Pour it all at once to prevent the various screeds from yielding or stabilizing independently.
- If you've opted for the wheelbarrow, build a ramp so you can pour the concrete over the base, but make sure it doesn't move or disturb the formwork. The ramps can be made with boards of 5x10 cm section or with other long pieces of wood.
- For this phase it is best to have the help of some other person; you need someone to shovel the fresh concrete out of the wheelbarrow while you hold it up.
Step 3. Push the concrete into the corners using the shovel
It is a heavy material, so you must try to throw it near the area you want to cover. If you are making a large surface, you need to use a long-handled tool to reach the innermost points, or wear rubber boots and walk through the concrete as you rub it.
Step 4. Use a flat piece of wood or an aluminum straightedge (a long rod with a 5x10 cm section) to level the screed
Work from one end of the patio to the other in a horizontal motion.
It is best to perform this step with the help of another person
Step 5. Use a long handled trowel to smooth the surface
Move it back and forth on the concrete of the patio to fill in areas with a low level.
The water floats on the concrete during this process, to complete the patio construction you have to wait for the liquid to disappear
Step 6. Move on to the finishing touches
Use an edge trowel and run it between the formwork and the concrete to create a rounded profile. When the screed is able to support your body weight, make incisions every 2.5m. These are control joints that help the concrete move or change over time. The final step is to smooth the surface by hand with a magnesium or aluminum trowel to finish the patio.
Step 7. Wait for the concrete to season for at least two days
Cover it with a plastic sheet or a specific compound to make sure it stays moist; at the end of this process remove the boards of the formwork. Be very careful at this stage to avoid chipping the newly built screed.
Advice
- To improve stability and reduce the likelihood of cracks, install a mesh or metal armor forming a checkerboard before pouring the concrete.
- Always evaluate the weather conditions on the day you plan to pour concrete. The temperature and humidity of the air alter the hardening times of the material.
- If you live in a region with a particularly cold or humid climate, consider using air-entraining additives; these substances create air bubbles in the compound, they are invisible but allow the humidity to freeze without breaking the screed.
Warnings
- If the area affected by the concrete casting is greater than 3.5m in any direction, do not forget the joints. These elements should have a thickness equal to 1/4 of that of the screed and should be spaced 20 or 30 times the thickness of the concrete slab; for example, a 10 cm thick screed requires 2.5 cm joints placed every 2-3 m.
- Working with concrete is very dangerous; wear the right clothing when you build the patio. Long-sleeved pants and shirts are the best choice, don't forget gloves and goggles.
