The cost-cutting move comes as pressure grows on the training body to cancel this year’s levy to help out cash-strapped contractors.
The CITB raised £188m in levy payments from the industry last year.
It has suspended levy collection for at least three months during the coronavirus crisis.
But the National Federation of Builders is leading calls for the CITB to consider cancelling the 2020 levy.
The training body has confirmed it will be reducing its 834-strong workforce by 50%.
Jennifer King, CITB People Director, said: “We will re-scale our business to protect industry funds, reducing staffing levels by about 50% through furlough and other means, with some areas more heavily impacted than others.
“We’re informing affected staff this week. We have also implemented an all-staff freeze on annual pay increase, with the Executive Team having already taken a voluntary pay cut.”
Latest accounts for the CITB show it had £64.8m in reserves.
King added: “Construction is under extreme pressure right now so we’ve taken several steps to provide financial relief to support it to retain skills.
“These include suspending issuing levy bills for at least three months and paying apprenticeship attendance grants in advance.
“We’re adapting funding rules where we can and are reviewing all our services, including enabling teaching of courses through remote learning.
“We will maintain financial support for skills development in the industry and also prioritise our other services.
The CITB has also announced a new £5m fund for “leadership and management development.”
The new fund is aimed at larger contractors with over 250 employees who can apply for grants of up to £100,000 to help train managers.