Pouring a concrete slab can be a challenging task, particularly for beginners. Factors like shape, size, color, complexity, and finish make every project different.
Read on to learn more about the various steps to pour a concrete slab, as this article will provide a comprehensive guide.
The first major part of the work of building a new slab includes excavation and form building. The builder needs to level out any sloped ground or fill it to increase the level of the ground.
Manual excavation is suitable for small sites, but excavators are mandatory for preparing the site for larger ones.
Next is estimating the volume of concrete necessary for laying the slab of a specific size. Finally, accurate calculations are required to estimate how much concrete mix is needed.
Preparing The Site
Before starting work at the site, clearance from the local building department is obligatory. It also gives an idea of how close to the plot lines the slab can be laid.
Now, roughly mark the four corners of the slab. Next, directly measure the location and approximate size with the line level to understand the amount of slope in the ground.
Understanding The Type Of Soil
If the site contains sandy soil, then it’s favorable for laying concrete slabs. The chances of cracking in sandy soil are significantly less because the water content of the ground is low.
It is best to create a 6-8 inch layer of compacted gravel for loamy or clay-like soil. Putting a layer of gravel under the concrete protects it from excess moisture.
Selecting Boards To Prepare Forms
After preparing the site, the next step involves the selection of straight-form boards. For slabs that are 5 inches, thick 2×12 boards are perfect. However, for laying thick slabs, contractors mostly use 2×6 boards.
If the boards are not long enough, it is best to merge the boards with nails. The joint of the boards should be properly aligned so that the final slab has a clean finish.
Contractors use durable braces so that the boards don’t fall out of place when pouring the concrete. In some cases, the slabs have a curved edge which becomes quite challenging to fix.
Typically, stakes and kickers are placed every two feet along the length of the board to give extra support. In addition, kickers prevent the stakes from bending outwards.
Setting The Form Boards
Use a Mason’s line to stretch the top end of the form boards. Always check that the braces are in alignment with the string.
Next, adjust the braces so that the boards are straight under the top section of the forms. For proper leveling of the structure, place one board higher than the other and hammer them into place.
Adjust the level by gently tapping on the stake until it reaches the right level.
Building And Packing The Ground
For building a solid foundation, proper draining of the base level is necessary. The presence of excess water in the concrete structure can result in cracks and movement inside the concrete slab.
For sandy soil, there is no need to prepare a gravel layer. The sand absorbs an extra amount of water. For other types of soils, adding a layer of gravel is mandatory.
After the forms are set in place, take proper measurements of how much concrete will be necessary. Contractors often use crushed concrete, as it has a suitable absorption property and also drains well.
Spreading The Concrete Mix
While spreading the concrete mix, a 3-inch thickness is ideal. Plate compactors help in tamping all the layers together. A 12-inch wide and 12-inch deep trench is necessary for the thickened edges.
Reinforcing With Steel Bars
Most concrete structures require reinforcements to eliminate the chances of cracks. It also enhances the strength and durability of the structure.
Professional contractors use composite metal decking for lining heavy structures. It has become the most popular method of reinforcing structures for commercial construction.
For small domestic applications, reinforced bars are perfect for increasing the strength of concrete slabs.
Cutting Steel Bars
Metal cutting blades and power tools are used for accurately cutting the path to the desired length. Next, the bars are laid into the structure’s perimeter and secured with wire for joining or overlapping.
Next, a 4-foot grid is formed with wires at the center for pouring the concrete mix.
Keeping An Eye On Weather Conditions
Concrete structures dry fast in hot weather, so when pouring concrete in warm temperatures, it is best to pour in small amounts.
Pouring The Concrete
When pouring freshly prepared concrete, always try to drop the mix in the final spot and smooth with a square head shovel. Lift the bars and position them in the middle of the slab simultaneously with the pouring process.
Once the concrete is filled in the forms, use a screed board to smooth off the surface. Avoid shifting an extra amount of concrete with the screed board, as it would result in poor finishing.
After the finishing is done, use a bull float to eliminate the marks left by the screeder. It also feels in the gaps and creates a smooth surface. Avoid creating low spots.
Giving A Smooth Finish
After bull-floating, the concrete water rises to the top. Bleeding of the concrete structure helps in the hardening process.
Press the top surface with the thumb to check whether a design is ready for hand-floating. Once the concrete is stable enough to take the full weight, start the grooving process.
If the grooves are not made, cracks can appear on the structure due to shrinkage. To achieve a smooth finish, continue to float using a trowel. This helps in removing all types of imperfections and gives a perfectly smooth finish.
After the smoothing process, keep the structure moist to facilitate proper curing until the design attains full strength.
One can use water or chemical-based curing compounds for this purpose. The concrete structure takes around 24 hours to harden during the curing phase.
Following the steps mentioned above will surely help in building smooth and durable concrete slabs of any size.
It may be difficult for first-timers, but contractors learn the appropriate techniques and tricks of laying a concrete slab over time.