DIY Artificial turf installation step three: What base is artificial turf laid on and why is it important
Artificial turf installations in your backyard needs to be laid on a minimum of 90mm of GAP20 basecourse (crushed rock), with a 10mm blinding of GAP7 to get the final finish smooth and level.
The grading of the basecourse is very important. When levelled and compacted the GAP20 (maximum aggregate size is 20mm) is very strong and when laid over geotextile cloth will provide an extremely stable base ready for your artificial turf to be laid over the top. As a comparison 100mm of GAP7 (maximum aggregate size is 7mm) will not bind together tightly as the aggregate size is too small and extremely mobile, this layer will be weak and will move easily as the years go by resulting in your turf subsiding and getting creasing and indentations.
If this is a DIY project make sure you ask for GAP20 at your local landscape supplies store, if you’re engaging a contractor make sure you select carefully and ask if they’re priced to use 100mm of GAP20 with GAP7 as final screed.