After a harsh winter with temperature fluctuations, we often get inquiries from homeowners with this problem - a cracked patio.
Reasons your concrete patio may be cracking
Water accumulating underneath due to poor drainage
As a first step in construction, it is essential to grade the subsoil so that water will drain away from the patio. If the surrounding land slopes toward the patio, then curtain drains need to be installed to catch the water and divert it.
A minimum of 8″ of compacted gravel needs to be installed as a base under the patio. This helps to keep ground water from pushing up as it freezes and heaving the concrete.
Steel reinforcement bars (rebar) are needed to hold the concrete together. The amount and spacing of the rebar depends on the size of the patio. They need to be tied together so they act better as a unit. While rebar itself does not prevent cracking, it minimizes any cracks that might form.
Lack of expansion joints
Concrete is affected by temperature. Flexible expansion joints at defined areas allow the concrete to move and touch without breaking. Just think of a rubber door bumper cushioning the impact of the door being flung open, for example.
Lack of perimeter frost wall
Think of a perimeter frost wall as a foundation frame on which the concrete slab sits. It provides stability and helps to keep water away from the patio, too.
Wrong materials or technique
Concrete stability will be affected by temperature, the type of cement, the water-cement ratio and the type of aggregate used during construction of the slab. Concrete should have a minimum of a 3000psi rating.