The trade body said finally securing a deal “brings reassurance to the construction industry” but noted for some it was already too late.
It also warned that the vast majority of the industry was already seeing higher costs and supply chain delays.
FMB chief executive Brian Berry said: “After the toughest of years, Britain’s builders will welcome the certainty that this deal appears to offer.
“Unfortunately, however, the deal will have come too late for many already feeling the effects of prolonged indecision.”
Berry added: “Nine in ten builders already face risings costs due to supply chain disruptions and higher product demand.
“We will wait to digest the detail, but this trade deal must deliver for builders by removing the barriers in their path to building back better and greener, be those access to products or skilled labour.”