This article is about how to dig a foundation for a house, deck or any other construction. Digging a foundation is essential for the rigidity and durability of your construction on the long run, so it is important to pay attention to our step by step diy guide. Remember that you have to hire a qualified engineer to determine the depth of your foundation, as well as the number and complexity of the reinforcing bars you are going to use. Nevertheless, in this article we show you several basic techniques, when talking about digging a foundation.
You have to understand that the soil structure influences to a great extent the depth and size of your foundation. For example, in most of the cases, you will have to build pillars if you have an infill site. On the other hand, for an average soil you have to dig 3-4′ deep and 2′ wide tranches. Therefore, it is better to evaluate the quality of the soil before purchasing it, or before deciding to build a construction. Before digging a foundation, you have to prepare the site thoroughly. Consequently, you have to remove the trees and most importantly their roots. Nevertheless, you have to comply with the local regulation regarding these issues, otherwise you risk a significant fine. If on your site there are a lot of old trees, it would be a good decision to search for another land, as it is very expensive and time-consuming to cut trees, transport them and remove their roots from the ground.
In order to dig the foundation, you have two main options: renting a hydraulic digger, or hire several people to dig the trenches by using shovels. Obviously, the first alternative will do the job quickly, but there are cases in which a hydraulic digger might not have access to narrow or isolated sites. In that case, the only solution is to hire 3-4 persons to dig the foundation by using shovels. From our experience, digging a foundation with shovels is better and cheaper than renting a digger. First of all, the trenches might collapse while using the machinery and secondly, you have more control when using the shovels. Nevertheless, if we speak of a large foundation, a digger is the best choice.
In order to dig a foundation, you need the following:
- 1×4 lumber to build the batter boards
- safety gloves, glasses
- measuring tape, carpentry pencil
- hand saw/circular saw
- spirit level
- pound the natter boards into ground, for at least 16”/50 cm
- clean thoroughly your tools after you have finished the project
- several days, according to the surface of the foundation
Laying out the house foundation
The first step is to lay the foundation of your house. In order to do a proper job, you need to construct two batter boards for each outside corner of the foundation. In order to build batter boards you need either 1×4 or 2×4 lumber, several nails and a hammer. Remember that the batter boards have to be rigid, otherwise while digging the foundation you might move them from the right position. In addition, you have to fasten squarely a crosspiece over the two stakes.
Next, you have to lay out the perimeter of your house, but you must ensure it is exactly over the location written in your construction permits. Even the slightest error will make your life miserable, so pay attention when installing the batter boards and laying out the foundation perimeter.
Smart tip: measure the sides of the perimeter to make sure they are right. In addition you have to measure both diagonals to check if they are equal. If they are not even, you have to install again the batter boards and the string lines.
Next, you have to check if the corners are square by using the well-known 3-4-5 method. Starting with one corner, you have to measure along one side 3′ and make a mark on the string. Next, measure 4′ along the other side of the corner and make a mark again. Then, you have to measure the distance between the two marks. If the distance between the two marks is 5′, then your corner is perfectly square, if not you have to redo the previous steps until your layout is perfect. You have to apply the 3-4-5 technique for at least 3 corners of the layout. Check again if the diagonals are equal.
How to dig a foundation
After you have made sure the layout of your house is perfect, you can start digging the foundation. As we have already said, there are cases in which you cannot rent a hydraulic digger, so you have to use the traditional method: digging the footings with shovels. Although it might seem a straight forward process, we can assure you it is complicated, but if you pay attention to our guidelines, you will pull it through easily.
First, you have to mark the footprint of your foundation on the ground. In this way you will make sure the footings will be straight. However, we have to emphasize that you must read carefully the foundation plans, as to dig the foundation properly. Another aspect you have to take into account is to prepare a site, near the foundation, where to deposit the soil you excavate from the trenches.
Smart tip: before digging the foundation, you have to remove the plants that are in the way of your house. Consequently, use shovels and saws to remove their roots.
If you have to dig a foundation near your house, you have to pay special attention to the operation, as it might affect the structural rigidity of your house. Consequently, you have to make sure you don’t dig under the foundation of the house , to ensure you don’t damage it.
Work attentively and with patience, as any mistake you make will amplify when building the actual house. Strange as it might seem, there are many persons who think that the foundation is not important, as it’s not visible. Nothing can be more wrong, so make sure you build the foundation according to the plans, as your safety is at stake.
Smart tip: when extending your house, in most of the cases you will also have to strengthen the foundation of your old house, to make sure it will support the higher forces exercised by the new construction.
If there concrete stamps on the site of your foundation, you will have to break them with a jackhammer. This is the easiest and most efficient method to break concrete, but you can also use a sledge-hammer. It will do the same thing, but you have to put more effort and it is time consuming, that is why we kindly recommend you to rent a jack hammer for a day or so.
Smart tip: while you are using the jackhammer make sure you use safety glasses and ear protections.
Continue digging the foundation according to the plans, and make sure you deposit the soil near the construction site, as you will be needing a significant amount to fill in the foundation.
Smart tip: the rest of the soil excavated from the footings can be used to make great landscaping projects. Nevertheless, if you don’t need it at all, you can give it away to someone who could use it in his garden.
You can transport the soil from the foundation, by using a wheelbarrow. The wheelbarrow is a great tool, as it allows to to deposit the soil near the construction site, without putting too much effort.
Smart tip: make sure the wheel is properly inflated, otherwise it would be harder to move the soil.
If you have to transport the soil or just walk over the foundation trenches it would be a good idea to make a bridge, by using two thick wooden boards (2×4 lumber) locked together at both ends with two pieces of 1×2 wooden boards.
Smart tip: make sure you surround the foundation trenches with a fence during nights, as people or animals might get injured or trapped if they fall in the trenches.
When digging a foundation, it important to make sure its bottom is perfectly level. There are cases in which the site is not level, so it is hard to tell by eye if the bottom of the foundation is perfectly level on the whole surface. Nevertheless, we will show you a techniques which works in any situation.
Just use a laser level or a water level to make visible marks on four posts installed at each corner of the foundation. Next, use a tape measurement to see the distance from the marks to the bottom of your foundation trenches. If the four depths are equal, it means the corners of your foundation are level. If the depths are different, you have to adjust them accordingly.
Read more about how to build the formwork for a foundation.
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