What are House Footings
Footings are the first part of a house that is built, and they stop your house shifting from its intended position.
Every new house and extension will need new footings, the footings will need to be specified by an engineer ( or possibly architect if they are very straight forward). There are a number of factors which will determine the type of foundations you will need.
Each site is unique, the slope, soil type and rock position will all affect the design of your footings. If there is any slope to your site you may need to do some cut and fill excavation or you may have a site with uneven rock under the soil. Footings need to have even bearing on solid ground, this means that the concrete needs to sit on rock or very hard compacted earth. When you dig down into the earth you may find a rock shelf a metre or a few metres under the ground if this is at different levels around the perimeter of the footing you will probably need a pier and beam footing. All these circumstances my be difficult to predict until you have begun excavation, but a few holes dug nearby and a talk with your engineer of architect will help you to know what to expect. .
The excavation of footings will be done with a bobcat or excavator. If you need to drill piers then the excavator that you hire will need to have a orger bit attachment. You may need to consider how the excavator will access your site and where the excavated earth will go, are there some garden beds planned for near the house? If your site needs cut and fill this will have council restrictions so make sure that it is carefully planned and communicated to the excavator. The earth which is moved to the 'fill' part of the site will need to be compacted to engineers specifications.
Footings support the weight of your house and therefore hold it together. If unsuitable footings are built for a house, the end result is that the house will crack, become unlevel, or in the worst cases eventually become uninhabitable or fall down.
Unfortunately, some people have discounted the importance of building good footings because they are not a visual component, and have gone for cost cutting methods which ultimately cost them a lot of money in repair bills down the track. Others have used substantial foundations which are not suitable to their particular site, and that causes problems at a later date too. Screw Piling is a technological solution which differs from traditional methods.
It is important not to put the rest of your building investment at risk... Build your footings right the first time!!
How to Decide Which Footing System to Use:
This depends on two things:
1.The type of house you are building:
If you are building a house which includes many of the following, then your house will be heavy. This means that your footing system will need to be substantial to handle the higher loads, and will typically come at an increased cost.
If you are building a house which includes many of the following, then your house will be lighter and you will be able to use a foundation system which typically would not cost as much.
- Concrete slabs
- Double brick walls (known as "full-brick")
- Multi-storey (particularly if concrete slabs are used for floors at all levels)
- Tile roofing
- Large load-bearing concrete columns and walls ("framing").
2. The type of ground you are building on:
- Steel frame (advantage is they are truly straight, and unaffected by vermin)
- Timber frame
- Virtually any floor system which is not concrete
- Cladded walls (metal or timber)
- Metal roofing
Determining the type of ground conditions which your site may have is something that should be done by a professional Geotechnical Engineer. This really ought to be done before you buy your home site, because if it is found that the ground is "weak", then it is likely that more extensive foundation systems are needed which typically come at a greater cost. Prior planning will save you money.
This may give you some bargaining leverage for negotiating the purchase price of your site.
You can find Geotechnical Engineers in your local directory under Geotechnical Services. For a modest fee, these companies specialise in determining what the underlying ground conditions on building sites are and how "strong" the ground is, and can then give you a range of options from which to choose your most suitable foundation system. The first shortcut most people take is to not get geotechnical advice. Geotechnical advice is money well spent, as it ensures your foundations will not be under designed (and fail), or over designed (and cost more than they should have).