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Foundation footings

Installation   In the footings   Pouring the concrete   After the concrete is poured                                   
Formwork
You are now ready to build the spread footings on which the foundation walls will rest. This section outlines the steps to follow, from assembling the formwork to pouring the concrete.

Having excavated the site, you can now assemble the formwork for the footings. The spread footings play a specific load-bearing role inasmuch as they support the weight of the house, through the posts or foundation walls, and then redistribute it to the ground. When planning the type and size of the footings, be sure to consider the type of soil in which the concrete will be poured (clay, marsh, etc.). At the very least, footings must be deep enough so that the concrete is poured below the frost line.
  • Installation
Installation
Footings should be 76.2 cm (30 in) wide and 25.4 cm (10 in) high. They must be centered according to the foundation’s future walls.

In order to install your footings, first drive retaining stakes into the ground with the help of a sledgehammer. Then nail the 5.08 cm x 25.4 cm (2 in x 10 in) boards to the stakes, one behind the other, to build the formwork.

Don’t forget to install footings for steel posts, fireplaces and masonry chimneys that are on your foundation plan while installing the footings for the main foundations. After the concrete has been poured, you will need to insert bolts into the footings that will be used later to secure posts.
  • In the footings
Before pouring the concrete, dig a trench to pass the water intake, drainage and sewage pipes that will connected to public utilities under the foundations. Avoid digging this trench in areas that have to support particularly heavy loads. After the pipes have been installed, cover the trench with machine-compacted gravel or with a light pour of concrete.

Then prepare pieces of wood measuring 5.08 cm x 10.16 cm (2 in x 4 in) that will be used to create a notch in the fresh concrete on top of the footings, called a key. The key increases the wall’s resistance to soil pressure and effectively prevents water infiltrations between the footings and the foundations. When cutting the wood, make sure the sides slope slightly, eventually forming a lozenge-shaped groove.

After completing this step, insert two concrete reinforcing bars, 1.27 cm (1/2 in) in diameter, inside the footings’ formwork. The bars should rest on 3.81 cm (1 ½ in) wooden supports and be tied to them with metal wire.

Now is the time to prepare the footings for the pipe leading to the garage drain. To do this, cut a piece of PVC pipe, 15.24 cm (6 in) in diameter, whose length equals the width of the footings’ formwork.

In the footings In the footings
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  • Pouring the concrete
Pouring the concrete
You are now ready to have the concrete poured. Before doing so, make sure your formwork is solid enough to withstand the pressure of the concrete. Fragile formworks tend to shift under pressure from the concrete. To avoid that, nail 15.24 cm (6 in) boards across the top of the formwork. Also ensure that the inside of the formwork is free of foreign substances such as sawdust or water. And don’t forget to check that the concrete reinforcing bars are solidly tied to the wooden posts. If they’re not, they may shift during the pouring operation causing serious damage to the footings. Now is the time to choose the type of concrete you will use. Many contractors recommend 25-MPa concrete. MPa (megapascal) is a measure of the compressive strength of concrete. Don’t forget that the foundations are meant to support your new house!

As concrete is being poured into the formwork, spread it evenly with a shovel or a rake. This is important if you want the concrete to fill all the footings and form a consistent block without defects.
  • After the concrete is poured
After the concrete is poured
Take advantage of the soft concrete to install the 5.08 cm x 10.16 cm ( 2 in x 4 in) pieces of wood, that you have already prepared, in the centre of the footings to mould the keys. Don’t forget to leave a space between each piece of wood to allow for the subsequent installation of L-shaped reinforcing bars. These bars serve as a mechanical link between the walls and the footings. Place the bars on the concrete’s surface leaving 1.22 m (4 ft ) between each.

The concrete footings are now ready for curing, which is the time required for the concrete to dry. Note that the duration of the curing period depends on the temperature and the humidity, which vary depending on the season. It’s always better to wait a few days, up to a maximum of one week, before removing the formwork from the footings.

Finally, backfill the surface within the formwork’s perimeter. This step is critical and must be done before building the formwork for the foundations walls. To backfill, use 1.90 cm (0-3/4 in) gravel.
After the concrete is poured
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