The firm plans to bring back factory staff from the start of next week for a phased reopening of some factories over the following weeks.
The decision to follow Michelmersh back into production leaves just Forterra, supplier of London and Butterley brick on shutdown.
Although it said it could resume production of bricks and blocks within seven days of a decision to restart.
Ibstock said it would introduce enhanced protocols to ensure compliance with social distancing, hygiene and current guidelines regarding Covid-19.
All sites will undergo a “safe-start” session before commencing operations to support these ongoing protective measures.
Joe Hudson, Ibstock’s chief executive, said: “It’s at times like this that the relationships which we have with our customers and across the supply chain demonstrate their most significant value and increase the combined strength of all our businesses.”
He added: “Over the last 18 months Ibstock has invested significantly in the reliability and capacity of our assets.
“As a result, we have good stock levels and are confident that by working together with our partners we can continue to meet your needs through this restart period.
“We have continued to despatch product for essential projects and have done this in a safe and effective way.
“With enquiries increasing, our commercial teams are available and continue to work remotely to process orders and payments, and to respond to your questions as required.”