Did your concrete patio heave from frost forming underneath, this past winter? The following information will remedy this problem before next winter.
Concrete slabs poured for patios, sidewalks or large areas like driveways should have the ground around graded so water drains away from not towards the concrete. If water doesn't drain away it will run up to the side of the slab and then migrate under the concrete to sit and wait for cold frosty nights causing frost heave. This will sometimes cause major cracks in concrete. To correct a drainage problem around a slab, dig a trench beside the concrete slab or sidewalk 8" wide and 18" deep. Line this trench with black landscape fabric leaving enough overlap at the top to cover the width of the trench, fill the trench within 2" of the top with drain rock (not crushed rock). Fold the landscape fabric overtop of the drain rock topping off with topsoil and lawn seed or turf. This allows the water to drain off the slab and ground water running towards the slab to run down into the trench dissipating into the ground not under the slab to cause frost heave.