How to build wooden concrete forms

UK Home Improvement

How to Build Wooden Concrete Forms

Concrete needs to cure before it can hold its shape, so it needs to be poured into formwork that is the shape you need the finished slab of concrete to be. Making concrete forms is like building a mould which can either stay in place or be removed once the concrete has cured.

What Are Wooden Concrete Forms?

Wood is the material most commonly used for building a concrete form, it is lightweight, cost-effective and allows the concrete to move a little during the curing process. Building wooden concrete forms is usually the easiest to assemble and most versatile option. Good quality, sealed timber is the best sort of wood to use when making concrete forms. Ensuring the wood is sealed will prevent it from absorbing water from the concrete mix, which could cause the formwork to warp out of shape.

What Other Materials Can Be Used To Build Concrete Forms?

Depending on the application, other materials can also be used for building concrete forms. Steel is often used in commercial construction projects as it is extremely strong, especially on larger slab sizes. Steel used for formwork can also be reused again and again, or left in place as part of a reinforced structure or design feature. Another option for larger forms is to use resin-bonded plywood attached to a wooden frame, this is a relatively inexpensive option in comparison to steel, however it is much less durable and cannot be reused easily.

Fibreglass concrete forms are a fairly expensive option as they usually need to be custom ordered, however they are particularly useful for projects involving curved surfaces which would be difficult to make using steel or timber.

When Are Concrete Forms Used?

Concrete forms are used in many different types of concrete projects, from domestic projects like laying the foundations for a shed or creating some steps, to commercial projects such as building houses with poured concrete walls and floors.

Concrete forms are used whenever poured concrete needs to be contained within a specified area or shape, allowing it to cure to its full strength and become self-supporting.

Why Are Concrete Forms Important?

It is important to create the most accurate and strong concrete forms possible, they are a vital part of any project. Think of it simply like making a cake, you wouldn’t just pour cake mixture straight into the bottom of the oven and expect to create a brilliant birthday cake, would you?

Pouring concrete can be made simple using readymix concrete delivered at a time to suit you, directly to where it is needed. The proper preparation is vital, as removing a fully or partially cured concrete slab, or fixing one that has been laid incorrectly can be very costly

How To Build Wooden Concrete Forms

Step 1

The first step in how to make a concrete form is preparation. Plan the shape and size of your project, calculate the materials needed, and then lay the outline of the planned forms on the ground. Ensure the ground is level and compact, and check your measurements are accurate, remember ‘measure twice, cut once’.

Step 2

At the corners of your outline, drive wooden stakes into the ground and use string to create the edges. At this stage it is important to ensure the ground is even and the stakes are correctly positioned by making sure the string is pulled tight. Use a builder’s level and double check all measurements again.

Step 3

Use the string line to position your treated wooden boards, the boards should be placed on the outside of the string line. You should also ensure the thickness of the wood is enough to hold the depth of the slab you are pouring. As a rough guide, a 4×1 inch board will usually be thick enough to support a slab up to four inches deep. Deeper slabs require deeper and thicker timber to be used when making concrete forms.

Step 4

Drive stakes into the ground along each side of the wooden concrete form. These stakes will support the formwork when the concrete is poured. Spacing one stake at least every 32 inches is usually adequate for a four-inch-thick slab. You’ll need to decrease the size of the gap between each stake for a deeper slab, or if you are working on loose soil.

Step 5

Once the form and all supporting stakes are in place, you can begin to pour the concrete. A slow and steady pour is best, making sure all corners of the form are filled and using the string as a marker for height. Once poured, let the concrete cure for a minimum of 48 hours before attempting to walk on it. Wait for three to four days before removing the forms; the slab will continue curing and will reach its full strength after around 28 days.

Making concrete forms that are accurate, strong and perfectly prepared will help to ensure your concrete project is a success. If you take just a little extra time to measure and build concrete forms to the correct specification, you’ll save yourself a lot of time and money in the long run.


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