Porters, cleaners, switchboard and catering workers at Cumberland infirmary are poised to take action over unsocial hours payments.
Two 24-hour strikes are set for 26 February and 1 March.
The workers are contracted to outsourcers Mitie.
The workers, who are members of the Unison union, are employed by private contractor Engie Services and earn as little as £8.72 an hour—with under 25s taking home even less.
The contracts force the porters on a system of eight rotating shifts. Workers say the new rotas will stop them looking after children and vulnerable family members.
The Unison union members have already struck for 18 days.
Birmingham Trades Council has organised an online solidarity rally for Sunday 21 February at 4pm.
Go to facebook.com/unisonheartlandsporters for more details
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