Concrete base pad vs Steel bearers & timber joists

[huckfinn]

Hi,

I'm raising my queenslander (80m2) in Cairns and need to build the future new ground floor (FFL 900mm of ground). The existing house is set 1.6mt above ground floor (i.e. the garden) and has blockwork all around the perimeter and good quality concrete slab (all under the house). I got a first quote (32k0 for a concrete base pad and, while waiting for other ones I wonder how a concrete pad would compare, price-wise, with a bearers (150pfc steel) and joists (125x50 f14 hwd) at 450center floor structure...?

Thanks!!

PS: if I went for the concrete I would do grinding + sealing, if timber either tiles or solid timber boards.

[MitchellMc]

Hi @huckfinn,

Are you looking for a comparison of material costs only, or are you factoring in installation as well? Labour is a significant part of construction costs, and it can vary quite a bit depending on the complexity of the job and local rates. To get an accurate comparison, you’d need to have the floor properly designed so that material calculations can be done—it’s difficult to estimate costs based purely on square meterage.

A concrete base pad typically costs more upfront due to excavation, reinforcing, and specialised labour, but it’s durable and low-maintenance once finished. A steel bearer and timber joist system can be cheaper in materials but may have higher labour costs and requires additional flooring like tiles or timber boards. Timber floors allow for easier access to services but may need more maintenance over time. If your site needs extensive earthworks, a raised floor could be more economical, while a concrete slab offers long-term durability. 

Your best option would be to get some quotes specifically for a bearer and joist system so you can compare it directly with the concrete slab quote you already have. 

Please let me know if you have any questions.

Mitchell

[huckfinn]

Thanks. So, concerning your points:

-Materials + labour

-No excavation required

-No major earthworks at all. And we must be 900mm above existing ground (garden)

[MitchellMc]

Thanks for clarifying, @huckfinn. Since you're looking at both materials and labour, the best way to compare costs would be to get quotes for a bearer and joist system, just as you've done for the concrete slab. While we can certainly help with materials once you've calculated them from a plan, installation costs will vary depending on the contractor, so it’s best to consult a builder or structural engineer to get an accurate estimate.

Mitchell