types of concrete slab:
What types of slab floors are there?
There are several different variations in slabs. The type of slab you’ll need will depend on the type of soil you’re building on, and how reactive it is. These types can be divided into many sub-categories, which depend on the type of materials that exist down to a certain depth in the soil you're building on. Generally, the following classifications are used:
Different classes of soil
Class A - This denotes very 'stable' ground - mostly sand and rock, not affected by moisture
Class S - Slightly reactive soil, slight movement due to moisture
Class M - Moderately reactive soil, moderate movement due to moisture
Class H - Highly reactive soil, a high amount of movement due to moisture
Class E - Extremely reactive soil, extreme movement due to moisture
Class P - 'Problem' soil, which experiences land slip, mine subsidence and so forth. If you are building on Class P site you will typically need to consult an engineer.
There are many different types of slabs too, but the most common variations are:
Slab on the ground - This is the simplest type of slab. It incorporates stiffening beams made from pre-poured concrete in trenches around the outside of the slab, and has a slab thickness of 100mm. This type of slab is suitable for Class A and Class S sites.
Stiffened raft slab - Similar to the slab on the ground, but also has pre-poured concrete beams set in channels through the middle of the slab, creating a kind of supporting grid of concrete on the base of the slab. Most slabs in Australia are stiffened raft slabs. The slabs may also need additional concrete footing embedded in the soil, depending on the soil type, and are generally suited to Class M, Class H and Class E soils.
Waffle raft slab (also known as a waffle pod slab) - These slabs are constructed entirely above the ground by pouring concrete over a grid of polystyrene blocks known as 'void forms'. Waffle raft slabs are generally suitable for sites with less reactive soil, use about 30% less concrete and 20% less steel than a stiffened raft slab, and are generally cheaper and easier to install than other types (even in bad weather). These types of slab are only suitable for very flat ground. On sloping ground or with more complex designs, a stiffened raft slab is normally the better option. Waffle raft slabs are suited to lightly and moderately reactive clay sites in particular, because they're not embedded in the ground like stiffened raft slabs. Waffle raft slabs are best suited for Class A, Class S, Class M, Class H and Class E soils (although you should consult an engineer about the suitability of the slab for very reactive soils, and generally to confirm this type of slab is suitable for your site).
Pier and slab - On sites with more reactive soils, it's common for concrete piers to be sunken into the soil to improve stability. This is normally done by digging holes at intervals and depths determined by an engineer, then pouring concrete into them and attaching the slab to these piers.
There are several different variations in slabs. The type of slab you’ll need will depend on the type of soil you’re building on, and how reactive it is. These types can be divided into many sub-categories, which depend on the type of materials that exist down to a certain depth in the soil you're building on. Generally, the following classifications are used:
Different classes of soil
Class A - This denotes very 'stable' ground - mostly sand and rock, not affected by moisture
Class S - Slightly reactive soil, slight movement due to moisture
Class M - Moderately reactive soil, moderate movement due to moisture
Class H - Highly reactive soil, a high amount of movement due to moisture
Class E - Extremely reactive soil, extreme movement due to moisture
Class P - 'Problem' soil, which experiences land slip, mine subsidence and so forth. If you are building on Class P site you will typically need to consult an engineer.
There are many different types of slabs too, but the most common variations are:
Slab on the ground - This is the simplest type of slab. It incorporates stiffening beams made from pre-poured concrete in trenches around the outside of the slab, and has a slab thickness of 100mm. This type of slab is suitable for Class A and Class S sites.
Stiffened raft slab - Similar to the slab on the ground, but also has pre-poured concrete beams set in channels through the middle of the slab, creating a kind of supporting grid of concrete on the base of the slab. Most slabs in Australia are stiffened raft slabs. The slabs may also need additional concrete footing embedded in the soil, depending on the soil type, and are generally suited to Class M, Class H and Class E soils.
Waffle raft slab (also known as a waffle pod slab) - These slabs are constructed entirely above the ground by pouring concrete over a grid of polystyrene blocks known as 'void forms'. Waffle raft slabs are generally suitable for sites with less reactive soil, use about 30% less concrete and 20% less steel than a stiffened raft slab, and are generally cheaper and easier to install than other types (even in bad weather). These types of slab are only suitable for very flat ground. On sloping ground or with more complex designs, a stiffened raft slab is normally the better option. Waffle raft slabs are suited to lightly and moderately reactive clay sites in particular, because they're not embedded in the ground like stiffened raft slabs. Waffle raft slabs are best suited for Class A, Class S, Class M, Class H and Class E soils (although you should consult an engineer about the suitability of the slab for very reactive soils, and generally to confirm this type of slab is suitable for your site).
Pier and slab - On sites with more reactive soils, it's common for concrete piers to be sunken into the soil to improve stability. This is normally done by digging holes at intervals and depths determined by an engineer, then pouring concrete into them and attaching the slab to these piers.