I want to build a new house, should I use the existing foundation of the old one?

Q:

I want to build a new house, should I use the existing foundation of the old one?

A:

You can build a new house on top of an existing foundation, the real question is should you build on an old foundation. That is a question that can only be answered by answering the following questions;

• What shape is the foundation in? You will have to get a professional to give you a report on what state your existing foundation is in currently. Is the foundation cracked, is it broken, is it crumbling? These are important questions that you might require an engineer’s report to tell you.

• What type of foundation is it? There are many different types of foundations; concrete, block, field stone and even rubble foundations. Depending on the type will depend if you can rebuild on it. A Rubble or field stone foundation will not allow you to rebuild on it. A block foundation can be rebuilt on but you can’t remove the wood floor above it without digging around the entire foundation to take the pressure off the building. A concrete foundation is the strongest foundation that there is, it will have more strength in it to survive the construction around it and the earth pressure once you remove the structure above it.

• Is the foundation of the old home functional? If you have a foundation that is not high enough for you to use then why would you bother keeping it. Reusing an old foundation almost guarantees that you won’t be using your basement as liveable space, that’s not the end of the world but it should be tall enough so that you can house the heating system of your home, the water treatment and also be used for storage.

• Does the size, shape and layout of the existing foundation conform to what you want to build? You won’t be able to differ too much from the existing building that you are going to tear down.  To make the building bigger you will have to add an addition to the concrete foundation. The other thing that you will have to understand is that when you redesign a building, changing roof lines and load bearing walls you will end up having to add footings and load bearing pads in the basement floor. This will require you to cut and remove parts of the existing concrete floor.

• Does the position of the existing foundation work? A lot of times older homes were built without surveys, they can actually be violating setbacks or even over a lot line. Is the foundation where you want your house to sit on the property? Sometimes an older foundation can be too close to the road or to close your neighbours. If you’re going to re-build a brand new house you’re going to want to make sure that the house faces the way you want it too, you might want the house turned so you can watch the sun set at night.
Using the old foundation could limit you and waste potential wonderful views or cause you to lose privacy.

The answers to these questions will answer if you should build a new house on your existing foundation or have it removed and start new. If too many of these answers are a no then you should think about just removing the old one and starting fresh.

If it’s a cost thing that you are worried about the removal of the existing foundation will not be much more then leaving it and building a new structure on top, depending on how and if you need to repair or alter it.

Rob Abbott
Operations Manager
Village Builders Inc.