An Oireachtas committee has heard that more than 900 schools are waiting for large scale building projects to be carried out by the Department of Education.

A department official told the Oireachtas Education and Skills Committee that in addition to the current 341 schools that are currently queued on the department's building list, there were a further 575 applications from schools that are not yet on the capital programme.

Responding to questions from Fianna Fáil Education Spokesperson Thomas Byrne, Assistant Secretary at the department Hubert Loftus said most of these applications were for major large scale works and were mostly refurbishments.

He said much of the backlog was because in recent years the department's focus had been on meeting growing demographic need.

Earlier, department officials told the committee of a "massive increase" in the number of new schools being built, as well as the funding that is being allocated for them.

Mr Loftus said that for the duration of the current National Development Plan, the Department of Education had a budget of €8.4bn. He said that this compared to €4.9bn under the previous plan.

Mr Loftus said that this year €540m would be spent on school building projects and more than €620m in 2019.

He said the increase in funding was enabling the department to focus on meeting growing demographic need and also on the refurbishment of existing school buildings.

Mr Loftus told politicians that there was a historic legacy of underinvestment in the sector "for decades" and that the department was "catching up".

Addressing concerns at the increasing use of prefabs in schools, Mr Loftus said that 1,300 classrooms were in prefabs currently, compared to about 2,000 classrooms in 2008.

He said the department had put 5,000 extra teachers into the system in recent years and that that had triggered an accommodation need.

Mr Loftus said the reliance of prefabs was also related to a legacy of past under-investment in school buildings.

Earlier, the committee heard from three schools who all described their pressing need for new school buildings.

Liam Burke, Principal of Whitecross National School in Julianstown, described finding a rat in a toilet during class time, a heavy storage heater falling off a wall in a classroom, "ad hoc" wiring, and "astronomical heating bills".

He said the school had been highlighting their unsatisfactory conditions since 2004 "and we still do not have our building".

Mr Burke said the school's ten prefabs were costing the state €80,000 in rent every year.

Brian Bergin, Principal of St Paul's Secondary School in Monasterevin, said the school had been included in a Public Private Partnership plan for new schools in 2005.

He said now they were told that construction would begin next year and be completed in 2021.

Describing the frustration of the intervening years, he asked: "How can we expect this completion date to materialise after the events of the past 13 years?"

The Deputy Principal of Ballinteer Educate Together, Muireann Carr, said the school had been opened in 2010 and was now in its second temporary home.

She said the school had 275 pupils and 250 on a waiting list for 60 places next year.

Ms Carr said the cause of delays in constructing a school building included a lack of joined up planning in the department.