Foundations in Residential Construction Homes

July 25, 2020

When investing your hard money, always ask your self what is the most important component on your investment? It will not be difficult to figure out that building foundation and structure will be the key component. Importance of good foundation is always very important in any construction may it be commercial or residential homes. A solid foundation is the base of any good quality building structure

What is a foundation in residential homes?

Foundations can be termed as natural ground or often NGL on which the building sits. The base of a home or a house provides a stable support and link for the remainder of structure to prevent any movements or falling over.

In engineering terms, a foundation is a element of which connects to the ground and transfers load from the structure to the ground. Foundations are either shallow or deep. Shallow foundations are individual footing, strip footing, raft or matt footings. Deep foundations are pile foundations or drilled shafts

What is the best foundation in residential homes?

The best foundation will depend on the land topography of your natural ground. Usually where the natural ground is stable with minimum cut and fill pier-based waffle pod slab foundations are built. This is because this type of foundation is cost effective choices and meet the engineering guide lines and Australian Standards

How is foundations and slabs designed?

Home foundations are designed by an engineer and take in to account by the soil, slope of the land and weight of the building that home is to be built on. Pior to engineer deciding on the type of slab and footing system a Geo tech soil report or investigation is conducted. This information is sometimes available from concerned land developer or council. The purpose of this soil tests or goe tech investigations is to find the bearing capacity of the soil and the level of reactivity to moisture conditions. It also depicts to the sub surface condition, ground water levels and foundation recommendations including founding levels.

This test is done by taking soil samples at different locations of lot area often know as bore holes. This soil samples are then tested in to a laboratory and classified into categories set out according to Australian Standards AS 2870- 2011, “ Resdentail Slabs and Footings – Constructions”

The site soil classification considerations are as follows:

  • A – Stable Non-Reactive, Affects Most sand and rock sites with little or no ground movement from moisture changes.
  • S – Slightly reactive clay sites, which may face only slight ground movement from moisture changes
  • M – Moderately reactive clay or silt sites, which may face moderate ground movement from moisture changes
  • H1– Highly reactive clay sites, which may face high ground movement from moisture changes
  • H2 – Highly reactive clay sites, which may face very high ground movement from moisture changes
  • E – Extremely reactive sites, which may face extreme ground movement from moisture changes
  • P – Problem soil – This type of sites may have inadequate bearing strength or where ground movement may be significantly affected by factors other than reactive soil movements due to moisture conditions. This type of sites also comprise soft or unstable foundations such as soft clay or silt or loose sands, landslip, mine subsidence, collapsing soils and soils subject to erosion. This category also includes sites that cannot be classified in any of the above classes

The soil classification will help an engineer or a builder to determine the concrete strength to be used, the dept of foundation and the grade of the steel to be used. The concrete strength usually used in waffle pods slab is 20- 25 MPA, however some slabs may require 32 MPA and steel is added to provide concrete more strength and stiffneess. Some portions of the slab may be designed with trench footings and steel mesh reinforcement to add more strength to the slab. The engineer designs square meshes by following sizes SL72, SL62, SL92 or SL 102.

The first number digit usually refers to the diameter of the mesh and the second number usually refers to the spacing. The higher the rating goes the mesh is stronger. In addition to this a concrete rib depth is determined that that has to be founded or laid on the ground such as 85mm, 90mm or 100mm thickness. The higher the number goes in thickness will incur deeper founding slab and a stronger slab

All foundations are usually founded in natural ground unless designed on an even bearing pressure. NGL or natural ground is referred to be the undisturbed ground on site. There different type of natural grounds on which piers can be founded n such as Red Clay, Red Brown Clay, Gray Clay or Shale Clay and rock bedding.    

What are the Costs involved in Foundations?

Foundations are sometimes charged on a Square meter rate or as part of fixed price foundations with a scope defined on excavation, carting of natural fill excavated from foundations, type of a slab soil classification and piering depth. Piles or piers are usually placed at every 2 meters or 1.5 meters depending on the site classification. However laying foundations is more than this fixed costs where experienced builders such as BUILDQ Group comes into play and consider factors such as drainage, heating and sealing. We also make sure that everything included in your house foundations upfront so in long run can save you more money. At Team BuildQ we have dedicated staff who always liaises with engineers and geo tech consultants to get you the best outcomes.

What do when purchasing or buying a land?

You can always make enquires with council and land developer on filling and conditions of the land or lot you are buying. You can ask for a geo tech investigation report. You can also purchase the land or lot or block of land with subject to soil test report to meet specified criteria allowing you not to proceed on sale of contract in an event of poor soil conditions, rock or contamination is found. You can even contact one of our friend staff at Team BuildQ on an advise or information on a particular land or lot for development