The Kilmarnock firm said it expects to create at least a dozen jobs across the next 18 months.
The long-established business was taken over by father-and-son team Angus and Greg McTaggart 18 months ago.
Greg McTaggart said: "Since we came in we have grown the roofing division by 600% and created a dozen jobs already.
"We would expect to do the same across the next 18 months. The funding is to give us additional working capital so we can grow the divisions. When we took over the business its main clientele was in the commercial plumbing side of things.
"Roofing and other building services were very, very small. We are redressing the balance and bringing in some other income streams so the roofing, maintenance and construction is on a par with the core plumbing business."
Mr McTaggart and his father had been looking for an investment after selling McTaggart Construction in 2007.
They knew the owner of Murchland & Company was retiring and felt the business was a good way back into the industry.
The company now employs around 40 people.
While Mr McTaggart admits the construction industry is still experiencing difficulties, he is hopeful of continuing to grow.
He added: "We are looking at new premises as we have outgrown where we are but we have not identified where we will move to yet.
"It would be a more modern office set up with an open yard and some stores. There are more opportunities in roofing and maintenance than in plumbing at the moment.
"In the longer term we also want to grow our core plumbing business but we can't do everything at once.
"So we want to maintain that at the level it is at and bring up construction, roofing and maintenance.
"Once they are on a par we will look at growing plumbing again."
Bank of Scotland has provided a loan of £250,000 and an overdraft facility of £100,000.
Evelyn McNair, relationship director at Bank of Scotland Commercial, said: "Greg and Angus are a great example of how strong family business partnerships can have a significant impact on the local economy.
"We have been able to develop a robust business and financing plan, meaning this Ayrshire company has a positive future and can continue to grow."
Contextual targeting label: