Host depleting in lan

I have recently joined a company and the complete network in in 192.168.0.0/22, Most of the ip addresses are statically assigned to hosts.
so now they are running out of ip address.

The dhcp range is 192.168.0.15-192.168.0.140 and next ip addresses are assigned to servers so they cannot expand the dhcp range. As a resolution want to move the network to 10.0.0.0 network.

What would be the best approach to increase no of hosts on network. should we change the subnet mask to /20 or move the network to 10.0.0.0 network.

And if I change the subnet to /20 what should be done about the fixed ip address servers and build machines for dhcp range