The England international has become a founding partner of the organisation after donating half a million pounds, which was raised from his testimonial match against Olympiacos in August.
"For all those who came along or supported me, it's nice for them to see exactly what their money has been spent on, and know that they too have all helped make this happen," Gerrard told the club's official website.
"It's a great privilege to be able to be involved with Alder Hey and their charity.
"The work they do is phenomenal and the new build looks set to be even more impressive, and maybe a little less daunting visually for the children."
The money donated from the Steven Gerrard Foundation will go towards a brain scanner for the Alder Hey hospital and a new play area for the patients.