Q&A / 

Concrete Footer Part 1 Video

Hello, I'm Tim Carter from AsktheBuilder.com. I'm here in New Hampshire on the western shore of Lake Winnisquam at a construction site. They are getting ready to build a garage for a residential home. And I am not in the hole and have something very interesting to show you that most people don't get to see because it happens so quickly.

What happened is yesterday they dug the hole in order to pour the footers. What we are seeing are the forms where the footer will be poured. First, what's a footer? The footer is the first thing that is generally constructed on a house build. It is the thing holds the foundation and spreads the weight of the entire structure over a larger area of the soil surface. This creates a wider footprint.

Image if you poured a foundation directly on the soil, if the soil got wet or the structure was very heavy, the foundation could cut through the soil like a knife blade goes through butter. But image if you turn the knife blade on its side and try to push it through the butter, you will find it will be very, very hard to get through the butter. That is what a foundation footer does.

Another thing a foundation footer does is provides a nice level surface so that the foundation forms can be placed with relative ease.

Let me show you two other things that are important with a footer. Down inside the footer forms are steel rods. These are 1/2" rebar. There are two rods that are suspended in the air. This allows the concrete to completely flow around the rebars. In addition, these rods go continuously around the footer. These steel rods give the concrete tremendous tensile strength so if the footer were to crack or try to separate, it would have to try and rip apart the steel bars. You can image how hard that is.

Look at this. The footer in the back corner has to go up to get over a section of solid rock. The footer had to jump up over the solid rock areas. Extra rods have been drilled into the rock so that the footer won't slide off the bedrock. Once the footer forms are past the bedrock, it drops back down to the original height.

So that is a concrete footer and what they look like before the concrete trucks show up. The footer is what supports the weight of your home. It is very important that these are installation correctly. The soil under the footer must be compacted completely and has past the soil inspection by the building officials. Make sure that happens on your job.

Continued in Concrete Footer Part 2.

SPONSORS / 

2 Responses to Concrete Footer Part 1 Video

  1. Tim - Pouring the concrete footing right on the big rocks is potentially a big mistake. As you know, soil can compress under the weight of a house. The idea of spread footings is to reduce this compression and to spread the pressure out evenly. Those rocks are not going to compress, at all. As the soil compresses, much of the weight of the house will go on the rocks much more than on the soil portions of the footing. Pressure points will form. And that is likely to lead to cracks in the foundation.

    Also, you referred to compacted soil under the footings. Bad idea. Footings should be poured only on undisturbed soil that nature has compacted over thousands of years, or engineered fill, such as gravel or other non-compressible material.

    Bill Hirsch

    • Bill, That foundation job was not mine. It was a garage being built near my home. The soil up here in NH in many locations is very strong. Builders up here routinely pour footings and foundations on a mix of ledge and soil and I've yet to see foundation issues. You may want to reach out to some structural engineers up here for some pointers on this. They deal with it daily.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>