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Essential to installing your foundation properly, backfilling is a delicate procedure that you should keep your eye on. Here’s what you should know.

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Building a new home is a long and complex process. You don’t need to be an engineer yourself to understand that. Nevertheless, you can benefit from getting to know a bit more about the process. After all, it’s best to understand what you’re coming up against if you encounter any type of construction problem in the future. Always be proactive when it comes to your home. 

Since we build our homes from the ground up, isn’t it logical to understand how foundations work? Well, we’d say so. No matter what size your new home is going to be, construction always begins with digging. So, before doing anything else, contractors will need to dig up the ground and lay down the groundwork. 

Once they pour the foundation, you’ll realize there are gaps and holes around it. Unfortunately, you can’t leave them there. The builders will need to fill them up with either the previously dug-up soil or other refill materials. Timing is key here because the foundation slab takes a little less than a week to cure and tighten up. 

In the following, we’ll go through the ins and outs of the backfill. Also, we’ll cover all the necessary details that you’ll need to know — from materials you can use to the whole process itself. 



The first thing you’ll need to know is what backfill is. Namely, it can be any material you choose to occupy the holes around the foundation slab and walls. You can use the already dug-up soil, a mixture of gravel and sand, or other commercial refill products. The type of backfill you choose will depend on a variety of factors. Nevertheless, the process of filling the trench should come in layers. Once you build the floor joints above the foundation, you can start to fill up the holes. 

Here is what proper backfilling can do for your home: 

  • Helps the substructure withstand the load of the home or building above it by increasing its strength 
  • Supports your home’s foundation 
  • Adds to the overall performance and stability of your home 
  • Assists exterior water drainage 

Types of Backfill 

Once again, backfill materials can vary. It all depends on the type of project you’re dealing with, as well as your drainage system. Your contractor may recommend and use one of the following types of backfill. 

  • Coarse-grained soil: A mixture of gravel, sandy soil, and a negligible amount of fine materials, coarse-grained soil is a high-quality type of backfill. It provides fine support for the foundation and is rather easy to compact. 
  • Limestone screenings: Great for sewer and pipe backfills, limestone screening is another type of material that compacts well. Also, you can use it as a base for brick paving. 
  • CA7 bedding stone: This is one of the most popular choices in the construction industry when it comes to backfilling. CA7 bedding stone is a grayish material that self-compacts so that you can also use it for bedding pipes, subbase work, and to improve soil drainage. 
  • CA6 base stone: A subbase granular backfill, CA6 is another great option to use. But besides residential projects, you can often see builders using it for roadway shoulders too. 
  • Trench backfill: Somewhat similar to CA6 base stone, trench backfill comes in the form of small aggregate that drains and compacts well. 
  • 3” coarse stones: When it comes to large holes and trenches, we would recommend using 3” coarse stones since they have great drainage properties. You can use it for the first layer of the backfill and later add the CA6 base stone for compaction. 
  • Commercial by-products: Sometimes, you can’t use the previously dug-up soil as it’s not compatible with your needs. So, if you come across this problem, our choice would be to opt for commercial by-products. This, of course, depends on the condition of the site and its engineering properties. 

The Backfilling Process 

Here’s how builders will backfill the holes around your foundation in five steps: 

  • First, they’ll need to clean the area that they’re going to backfill. While doing so, they will also pump out any water that’s stagnating there. 
  • The next step is to identify the materials with which they’ll fill out the holes and trenches. 
  • After choosing the backfill material, the contractor will pour it into the holes in consecutive layers of around 20 cm, beginning from the corners. 
  • Between refills, the contractor will need to compact the layers by using a roller or some other machine capable of such work. 
  • The final step is to further compact the layers with steel or wooden log rammers and water them. 

The Process of Compacting the Backfill 

In reality, no matter how well builders backfill the soil around the foundation, it will remain somewhat loose and could cause problems down the line. One of the most common issues you can have with it is the absorption of heavy rain or melting snow. Water will begin to push the walls of your foundation (crawl space or basement) in what’s called hydrostatic pressure

If such a scenario occurs, hydrostatic pressure will create cracks and fractures in the lower level of your home. Also, it can bow your walls, paving the way for costly repairs. But if you’re looking to avoid such things from happening, it’s important to backfill your foundation properly. Builders can do this for you by using adequate compaction equipment and suitable rollers. 

You Shouldn’t Risk Your Safety 

Unfortunately, backfilling can’t ever be as compact as virgin soil. If you’re looking to save yourself from possible problems in the future, you should contact professionals to help you backfill your foundation properly. 

Our team at Tar Heel Basement Systems is here to help if you have questions about your foundation or the soil around it. Contact us today to schedule a free inspection and repair quote. They’ll help assess the situation and recommend further steps that will keep your home free from leakage and other water-related issues. 

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