Builders' merchant Travis Perkins has said it plans to buy plumbing and heating company BSS Group.
In a joint statement, the firms said they were in "advanced discussions" after Travis Perkins made an indicative offer that valued BSS at £553m.
They said a deal would create the UK's leading trade and retail distribution business in plumbing and heating.
The BSS board said it would recommend an offer to shareholders if made on the same terms as the indicative offer.
It added that it had already spoken to some major investors who had indicated their support for the offer, which is made up of cash and shares.
Shares in BSS Group soared 34.5% to 437p while Travis Perkins shares were also up 6/1% to 790.5p in Friday trading.
Travis Perkins chief executive Geoff Cooper said he was confident that a deal would be struck and played down the prospect of a third party successfully bidding for BSS.
"We think we are in a position to drive more benefit out of this than anybody else, so we think it's a deal for us rather than anybody else," he said in an interview with the Reuters news agency.
However, Panmure Gordon analyst Andy Brown said other companies could be interested.
"There is high potential for a competing bid to emerge, as opportunities to acquire a business like BSS do not come around very often," he said in a note.
"If Travis Perkins succeeds at this level, we would view it as a very positive move for them."