When evaluating the cost of building on a difficult site, that is, one that has access issues, steep aspect or maybe a problem with ground water or soils that are classed as too weak to build on.
A good start would be to get a contractor, Engineer or Estimator that have experience with these types of sites – not everyone does. They should be able to run through options of what is and isn’t possible given what you are thinking of building.
They will also need to give you some estimate of construction costs.
Often, you will want an estimate of the site development cost before you purchase a section to decide if it is within your budget.
The house build itself is the easy part. Any builder, or Group home company can quickly give you a close cost to build the house itself. With sloping or difficult sites however, there are other factors that can influence the final costs, often to a large degree.
Site Assessment factors.
Access to building site – this impacts delivery of materials and could include the use of concrete pumps, hiabs even cranes to get building products in.
Earthworks – usually both more earth to excavate and depending on the site access can take more time to load onto the trucks. Both the slope of the ground and unsuitable soils, which may need to be removed, can influence the cost and quantity of site earthworks.
Retaining walls – often required for creating driveways and building platforms, there are many types of retaining wall systems and all vary in cost and their suitability.
Foundations – choosing the correct foundation system for your site can be crucial and will influence both the speed of foundations/ floor construction time and also cost. A little thought and searching for alternatives at the design stage would have resulted in big savings in time and cost.
Below the Foundations – it is possible that sites that are steep, have high water tables or underlying unstable soils will require engineered structures such as foundation piles – concrete and steel, driven or drilled / concreted poles, screw piles, concrete beams, grouted anchors, palisade walls or a combination.
The list can go on, and being structural items, sometimes the cost of these can make a huge difference to the overall job cost.
Reasonable estimates for development costs can be made for these difficult sites with the help of experienced advisors and gathering as much information as possible about the site.
Especially useful is a Geotech report, also survey plans and of course check the information that your local Council has on the property such as a LIM report.
Where desirable, Pole foundations are a cheap and inexpensive method of establishing foundations on sites with poor surface soils, embedding the poles into the underlaying suitable ground.
Get advise and options from people experienced in difficult sites.
Geotech report – obtaining a geotech report is a must for these sites. They will help with determining foundation type, retaining and earthworks requirements even at the initial stages and will determine the direction of the design and engineering.