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Story: Anita
Feb 12, 2019
Concrete slab vs posts with a sub-floor

Choosing the correct footings for your home is an important decision as it makes up a very significant part of the overall construction costs.

There are many factors to be considered ranging from personal preference to conditional regulations.

If your land is a very steep sloping block, then footings might be limited to a post and sub-floor option rather than a concrete slab. However, having a slightly sloping or flat block can give you the option of either posts and sub-floor or a concrete slab.

A major consideration when using a concrete slab on a sloping block will be the amount of works required which will reflect in the overall cost.  The land will require levelling out which generally involves cutting and back filling, retaining walls to support the cut and specialised waterproofing and drainage to prevent damp from rising. Depending upon the soil type, the slab may also require underpinning which involves deeper footings in the ground to support the concrete.

Posts and a sub-floor are generally the more cost-effective option when construction is on a sloping block. This type of footing will eliminate the need for cutting and filling, retaining and waterproofing. The footings may require deep beddings; however, this will be far more economical than an entire slab. There are now options available that eliminate the need for concrete altogether. This is an anchor footing system that is rammed into the earth. It is mounted with a base plate that the post is then bolted to.

Wind loadings, flood zones and high fire areas will also play a role in which footings will be best suited. A flood zone will generally regulate that you must use a post and sub-floor system. A high cyclone region will require additional bracing, a wider post thickness for an elevated system and more tie downs and bracing for a slab. A high fire zone will need under floor protection and generally require a fire-resistant sheeting for an elevated system.

When deciding upon posts or slab simply for aesthetics and for a flat to gentle sloped block, the cost difference is minimal. You outlay more for the kit materials when on a flooring system as we supply the posts, a steel sub-floor, internal floor sheeting and deck timber, however the amount of concrete is less so although the kit without a flooring system is a lot of less upfront costs, the concrete slab outlay is far higher.

So when selecting which footings to use, do your homework and consider all the factors as this is the foundation of your new home so you need to get it right.

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Yes. All standard plans can be modified to suit your needs. You can change the number of rooms, increase or decrease the size of the house or if you prefer, you can bring your own plans for costing. more »

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A full inclusions list can be found here. In general however, the kit includes all materials required for lockup but does not include on-site labour, transport and delivery charges, site survey, site clearing, PC items, concrete for footings, Electrical and plumbing etc. more »

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Delivery areas include all Australian states and territories. Arrangements can also be made for international deliveries excluding some countries. more »

In general how much could I expect to save if I decide to build a kit home as an owner builder?

As an owner builder/manager you are effectively cutting out the builder and therefore should make a saving of 20% to 30%. If you choose to be more hands on and undertake some of the manual tasks such as erecting the walls and roof trusses, installing windows, doors and painting the internal and externals etc, your savings will be increased further. more »

Is it hard to become an owner builder?

The process to obtain an owner builders permit is usually very straight forward. There are a few requirements and depending on which state you are building in, may also require you to undergo a short course (usually a weekend course), either online or at a training school. In most states a small application fee is payable. Click here for more owner builder information. more »

Are kit homes suitable for areas prone to cyclones?

Yes. Cyclonic kits can be purchased at an additional cost. These kits are manufactured with extra reinforcements that will make then suitable for areas prone to cyclones. All standard kits can be upgraded to cyclonic kits. All standard kits can be manufactured to meet with the cyclonic rating required for your area. more »

What is the turnaround time, from ordering the kit to onsite delivery?

This is determined by the size of the home. Generally we can have the kit on site within three to five weeks from time of ordering. more »

How will my kit home be delivered?

The entire kit can be delivered to your site in a shipping container, or part container and part by truck. Delivery can also be made in stages upon request. It is up to you what is more suited to your build plan. more »

How long does it take to build a kit home?

This depends upon the amount of labour and skill level. As a guide, a non-skilled owner builder can erect frames and roof trusses for an average size home in two to three days then the remainder of the build is similar to that of normal build times. A smaller kit can be built to lock up within a month. Larger, more complex homes will take longer. You should allow ten to twelve weeks on site for an average home. more »

Does the kit home come with warranty?

The steel frame is Backed by a 50 year BlueScope Steel warranty and all other components of the build have their individual manufacturers warranties. more »