How To Cut A Trench In A Concrete Slab


How To Cut A Trench in A Concrete Slab

There are many reasons that you might need to cut a concrete slab but doing so can seem like a daunting task to many. If that describes you, fear not! We are here to help.

Whether you are planning to cut a trench in a concrete slab in your basement, your patio, or anywhere else on your property, the process is relatively similar in every case.

To cut a trench in a concrete slab, it is best to use a dedicated concrete saw to get the job done. Not only will a concrete saw reduce the time and effort of cutting through the concrete, but it will also help control the amount of concrete dust created.

Materials Required

There are a few methods that you can use for cutting a trench in a concrete slab. This guide will focus on the easiest and most efficient way to cut through concrete.

The first thing that you will need to do is make sure you have all the necessary equipment. Here is a short list of the things you will need:

Smaller Projects

For smaller projects where concrete slabs less than 6” are to be cut, a circular saw with a diamond blade will do the trick. While abrasive blades can also work, it is likely that you will require many blade replacements as they wear out quickly. A Diamond blade, on the other hand, is much more reliable.

You can get a diamond blade ranging from around 4” to 18” and costing anywhere from $10 to $100, depending on your needs. Prices are comparable at a variety of home improvement stores, including Home Depot and Lowes.

Larger Projects

For larger projects, especially those that require a trench of more than 6-10 feet, a walk-behind wet saw is the best option. Wet saws are also the best for indoor work as long as there is enough space to operate the saw. Using a wet saw will also drastically reduce the amount of concrete dust that is created.

There are a variety of walk-behind wet saws. There is a heavy-duty option from Stark which is great for very large jobs, but smaller options like Skilsaw’s Mudesaw can also get the job done. If you do not wish to purchase the saw outright, you can also rent one for around $100 per day.

Safety Gear

As with any job involving heavy machinery, there are safety measures that should be taken when cutting a trench in a concrete slab.

Eye and Ear Protection

It is essential to protect your eyes from concrete debris while you are making your cuts. There is an enormous amount of dust created when cutting concrete and it tend to fly around quite a bit. Sawing through concrete is also very loud and some form of ear protection is required.

Filtration Mask

Concrete dust can cause damage to lungs. For that reason, it is important to wear a high filtration dust mask while cutting a trench in a concrete slab.

Knee Pads and Shin Guards

To protect your legs from concrete debris and accidental contact with the saw, knee pads and shin guards should be worn while operating the saw.

Heavy-Duty Boots and Gloves

Thick gloves designed for heavy work, as well as boots designed to protect your feet in extreme situations, should be worn while cutting concrete. Steel toed boots are commonly used for their added protective capabilities.

How to Cut a Trench in a Concrete Slab

The following steps outline the most common method for cutting a trench in a concrete slab. Your project may differ in size or scope, but the process will be similar.

Step One – Determine Which Equipment is Best for Your Project

Depending on the thickness of the concrete that needs to be cut, choosing the best saw for the job will help you immensely.

Using a circular saw with a 7” blade, for example, will allow for cuts up to about 2.5” in depth. Using a larger, walk-behind saw with a 14” blade allows for cuts of up to 5”. The cleanest cut will generally come from the larger, more powerful saws.

Step Two – Dust Management

As previously mentioned, cutting through concrete is an extremely dusty endeavor. Whether you are cutting a trench in concrete slab indoors or outdoors, you will have to think about how to manage the dust.

Dust is a more significant issue when sawing indoors. For that reason, it is common practice to use plastic sheeting and duct tape to seal off the space before cutting. Doing so will protect the rest of the house from being covered in concrete dust.

Step Three – Prepare the Concrete Slab

Before cutting a trench, clear the slab of any and all obstructions. While you may be tempted to remove spray paint or other marking from the concrete slab before cutting, it is not necessary unless the paint obscures the concrete slab in such a way to make it difficult to see the guide lines that you will use.

Once clear, it is time to measure and mark the trench that you will cut. Chalk is a common choice when marking concrete as it is inexpensive and easy to create perfectly straight lines. When using a chalk reel kit to make your lines, it is good to go back over your lines to make them as thick and bold as possible.

Step Four – Create a Guide Cut

After setting up your equipment and putting on all of your protective gear, it is time to get to work. Most concreate saws provide you with a way to adjust the depth of the saw blade. Adjust the saw so that you can achieve a cut of approximately half and inch deep.

Cutting a shallow line at first is both easier on the saw and makes it easier to control the saw. Cut concrete for no more than 45 seconds at a time as the blades tend to get hot fast.

Step Five – Finish Your Cuts

After the guide cuts are finished, you can then reset the depth of the blade to the depth of cut you require.

Being mindful of overheating (i.e. letting the blade cool down every 30-45 seconds), go over the guide cuts that you previously made with a deeper saw. Go slowly and maintain constant control over the cut.

Step Six – Remove Concrete from Trench

Once all the cuts are finished, you will need to remove the concrete in between the cuts. A sledgehammer is a popular choice for breaking up the concrete for removal but for larger jobs a jackhammer will also do the trick quite nicely.

Related Questions

Can you pour concrete next to existing slab?

You can pour concrete next to an existing slab of concrete. There are many ways to do this and there are a few different types of concrete, including Sakrete and Quikrete, that are good candidates for the task.

When I can I remove concrete formwork?

If you have built formwork for a new concrete pour you may be wondering how long the formwork should stay up. In general, concrete formwork should stay up for at least 24 hours, and up to 48 hours. Things to consider when determining the time required include humidity, grade, and temperature.

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