The firm confirmed that 217 jobs could be lost at Tallington, Lincolnshire and 106 in Henlade, Somerset.
The rest of the redundancies will be in Derby, Lound in Nottinghamshire and Dolyhir in Powys, Wales.
Tarmac has now started a 90-day consultation period over redundancies.
Tarmac Building Products chief executive Blair Illingworth said: “Tough underlying market conditions and continuing uncertainly of demand have led us to review the options for the future of our precast and flooring business, and we have taken the difficult decision to consider its closure.
“This affects five sites across the UK and, unfortunately, means that around 550 people are at risk of redundancy.
“It is not a decision we have taken lightly and we will begin a 90-day consultation period with employees affected by this.
“We will also liaise with our customers to discuss how this could impact them.”