PremierLine found that 31% of construction workers notch up almost 60 hours each week, with 3% putting in more than 70 hours.
The findings come after the government released figures showing that total working hours in Britain increased again for the first quarter of this year by 6.5 million. The total number of hours now worked each week is more than 900 million.
PremierLine chairman Barrie Wells said that small business owners needed to be aware of the implications of the trend towards working long hours.
He said: "Overworking can have a knock-on effect and employers need to think long term to prevent issues such as long-term illness or stress. Issues such as health and safety – in particular the hours put in by all staff – are high on the employment agenda."
Wells said: "What this adds up to is a very tough lot for the majority of small owner-managed businesses in this country. They are embattled by legislation, they suffer losses through crime and they don't feel the government is doing enough to remove red tape."
The survey also found that 22% of respondents in the industry took fewer than 10 days annual leave, with only 30% taking the average 20 days or more.
When the heads of firms were questioned about what aspect of running a business caused the most stress, almost a third said administration, with another 19% claiming legislation caused the most headaches.
A Building article in January on stress in the industry found that bosses of smaller enterprises were as prone to heart attacks as the heads of major firms. Ian Davis, director-general of the Federation of Master Builders, pointed out that smaller builders usually have a single managing director. According to Davis, many fail to take out insurance to cover against losses due to illness.
Davis said this could be the result of the industry's macho culture, which encourages pride in the amount of financial and business pressure bosses can endure.