It generally takes about 1 to 2 hours but it may take up to 3 depending on the circumstances. There are many factors that surround delays in installation. I would recommend you speak to your contractor and the company which will install your stone to work out all the details of the project in order for you to plan out your day and prepare for their arrival accordingly.
How long does an installation last? I have about 35 sqft and my contractor said about 3 hours. Is that right?
As Kinga stated, it varies per installation, so it's hard to judge exactly how long it will take, but three hours sounds about right for thorough installation where attention is paid to detail. Some other suggestions I can give you is to watch our Countertop Installation Checklist to make sure the installation was done properly. You can also educate yourself on the whole process in advance by watching our Granite Countertop Installation video. Hope this helps!