Depends. On who product you buy....
Tuff shed is the builder of the sheds that Home Depot sells. When purchased Tuff Shed will install it for you at no cost!
They usually contract with several third party contractors that perform that task for you.
No, they contact out. You could find a handy man to do it... maybe pay less but could take longer.
They contract with Tuff Shed. Tuff Shed will come install it at your chosen location. When they installed mine it was quick. 4 hours or so and there was a barn in my back yard.
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