The event will mark completion of a ten-year contract by Balfour worth £130m to finally finish painting the famous bridge.
Balfour construction chief Mike Peasland will attend the event with Scottish first minister Alex Salmond.
The twin memorials will pay tribute to the thousands of ‘Briggers’ who contributed to building, maintaining and restoring the structure in the 129 years since construction began – particularly those who died on the site.