4 Tips on How to Build Formwork for Concrete Slab Tips

by Robert Lewis professional speaker

Building the right formwork is one of the most important considerations for your concrete application. Thus, you should know the detailed and accurate process of building a formwork. 

 

1.    Determine the size of flat timbers

The process starts with choosing the right thickness of timber (or the material you are using). While you can use a flat timber of 2 x 6 (in) for a thickened edge, you can also use it in the size of 2 x 4. However, the dimensions mainly depend on what you are pouring. Anything that bears heavy load, for instance a driveway that will experience frequent traffic, the 2 by 6 dimension flat timber is better as it eliminates the risks of cracking. The flat timber pieces are fitted in a vertical manner.

 

2.    Ensure that there is sufficient slope

While building a formwork, what is critical is that you make sure that it has a sufficient amount of slope; meaning, you don’t want the water to sit there for birdbath. Most times you might notice a beautifully designed and textured concrete slab. But without sufficient slope, it is all for nothing if there is a big birdbath right in the middle of the slab. 

 

So, how much slope is sufficient? Well, it mainly depends on the stamp or stencil you use. The general rule of thumb is that for every 1 foot, you drop a quarter inch.  

 

3.    Ensure that the form is set to square

In addition to slope, what another thing is important is that on some patterns, you should ensure that your formwork (or form) is set to square. To check whether or not the form is really a square, measure the length of both diagonals. Both diagonals should be of the same length. 

 

In case the shape is not an ideal square, has some zigzag and you cannot check diagonals in a simple way, you will need to use the three-four-five (3-4-5) method. For instance, you can take the base and perpendicular length as 3 and 4, then the hypotenuse (or diagonal distance) must be five. 

 

You can use this concept for an indefinite number by doubling it (for example, 6-8-10 or 12-16-20) based on the size of the formwork. 

 

4.    Use the right stakes to hold the form 

With a stamped concrete pattern, you will need upright stakes. You might want them to drive down and flush to the top of the forms. If that is not possible because the subgrade is too compacted or dense, you might want to use a jigsaw or a hand saw and cut the stakes off flush so that stakes don’t disturb you when you start the formwork process. These stakes are designed with an aim to hold the form up or down or up to your elevation. 

 

Another kind of stakes used are called kicker stakes or bray stakes and they are fitted in a way so they hold the form properly when the pressure of concrete pushes out.  

 

By now, you can easily see that building formwork is a lot more than just throwing the forms on the ground. The next time you need to build formwork for concrete slab, follow the above guide and you will be able to avoid a lot of mistakes.  

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Created on Aug 18th 2020 00:08. Viewed 253 times.

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