Patios

Do you know why all those cement patios usually have
large cracks?
It's because in the colder climes the ground underneath
has frozen, & when the soil freezes the moisture expands &
pushes against the cement creating those ugly cracks.
Another reason is the absence of expansion joints in a
large piece of slab cement. The summer heat causes the
cement to expand & if it has no place to expand to, then
the result is always the same.
If you are contemplating a new patio then one way to
prevent them from happening is to pour cement footings
under the perimeter of the slab to a level below the historic
frost line plus install expansion joints when the patio is
poured. It's more expensive, of course, but this will usually
do the trick.
Small hairline cracks are inevitable in any cement slab but
the large cracks can be made to disappear.