State boarding schools in England are in "dire need" of capital investment, Roy Page, of the State Boarding School Association (SBSA), will argue.
Without investment, more schools may lose their boarding houses, Mr Page will tell the SBSA annual conference.
The government suggested schools could raise funds from charitable donations.
Thirty-eight state schools in England offer boarding, to a total of about 5,000 pupils.
In his speech Mr Page, chairman of the SBSA and head of the Royal Grammar School, High Wycombe, will list three state schools that have closed their boarding houses in recent years.Vital fabric
More may follow unless the government stumps up the capital for boarding accommodation, he will say.
Mr Page told BBC News that state boarding schools had received no funding to maintain their boarding houses under this government.Continue reading the main story
Some of our longest-established schools, run by experienced heads, are desperately anxious about the survival of their boarding houses”End Quote Roy Page State Boarding School Association He said his school, an academy, can apply to the Academies Capital Maintenance Fund, for its academic buildings but this does not cover boarding accommodation.
A recent government offer of grants to train boarding staff is welcome, he will tell the conference, but lack of money for "the literal, physical, bricks and mortar, the bedrooms and the dining rooms of boarding schools" may mean "we end up with wonderfully trained staff in buildings collapsing around them".
For two years the SBSA has been seeking "clarity and security from the government concerning capital investment in the fabric of state boarding schools", he will say.
"Some of our longest-established schools, run by experienced heads, are desperately anxious about the survival of their boarding houses."
He will argue that state boarding schools that care for vulnerable pupils, support ordinary families and prioritise armed forces' children are "a vital part" of the educational system.
He will add that lack of funding for boarding accommodation may mean "a boarding house may look more useful if converted into a sixth-form centre".Sharing standards
"It's not because the schools are badly managed, it's because they have no capital to maintain their buildings or improve their facilities."
Mr Page told BBC News that Ofsted sets minimum standards for boarding accommodation, which include numbers of pupils sharing a room and the numbers of showers and other facilities.He said funding per pupil in state boarding schools is around half the average annual fee charged by private boarding schools, which can top £32,000.
"State boarding schools are not allowed to make a profit. Neither are they allowed to borrow. To survive they need state support," he will say.
He is expected to question government plans to fund new state boarding schools when existing schools with expertise in boarding struggle to make ends meet.
A spokeswoman for the Department for Education said: "There is nothing to stop any school from accepting philanthropic donations.
"We know that state boarding schools make a valuable contribution to the education system and can change the lives of vulnerable young people."
She added that the government in England was spending £18 billion on school buildings "in this Parliament".
The spokeswoman said: "By next summer we will have collected up-to-date and reliable condition information for the entire schools estate to enable us to target this funding where it is most needed - including state boarding schools."