Heavy clay soil is a major problem for large portions of the UK. Clay soil particles swell in water, which inhibits drainage and makes the clay soil waterlogged. Because of this, plants that are not tolerant of standing water, including many turf varieties can develop root rot in heavy clay soils.To install a turf lawn on clay soil, you must amend the soil to improve drainage and use a turf variety that is tolerant of clay soils.
Remove between 10 and 20 soil samples from your lawn using a soil augur. Mix the soil and scatter it over a newspaper to dry. Then put 210 g (1 cup) of soil into a plastic bag and take it to a soil testing facility to analyse the structure. You can find a list of good soil testing facilities from your nearest county extension service. A soil analysis will tell you what percentage of your soil is clay, which soil amendments to add to improve the soil structure for a lawn and how much of each amendment to add. In general, it is best to add organic soil amendments such as peat moss, compost and composted manure to improve soil structure and increase drainage.
Prepare a bed for your turf by breaking up the soil to a depth of 30 cm (12 inches) with a rototiller. Add soil amendments in a 10 cm (4 inch) thick layer over your clay soil. Mix the amendments into the soil with the rototiller. Smooth and regrade your soil with a landscaping rake to remove divots. Water the soil bed 24 hours before laying turf.
Select a turf that is tolerant to a wide variety of soil conditions including clay or sand. Good examples of this kind of lawn grass include warm season grasses such as St. Augustine, Zoysia, Bermuda and Centipede grass. A good cool season turf grass is Fescue.
Lay the turf sod over your lawn as if you were laying carpet. Start along a straight edge such as a sidewalk or road and place the sod soil and root side down over the soil. Place the sod pieces so that they touch one another. Stagger the rows of sod like bricks on a home so that there is no uniform seam. Cut sod with a utility knife to fit around irregularly-shaped corners such as curves of flower beds or sewer grates.
Roll over the sod with a sod roller to force the roots of the turf into contact with the soil.
Water sod with a sprinkler up to four times daily with 6 mm (1/4 inch) of sod to keep the roots moist until they can become established. Use a rain gauge to measure the amount of water that you use each time.
Decrease the amount of water that you use after 14 days. Eventually you should water your lawn with only 2.5 cm (1 inch) of water every 10 days.