Herefordshire Council leaders are considering spending £1m more than expected to expand a popular county school.
Cabinet members had pledged £4,688,500 towards the extension of Marlbrook Primary School and a new car park last year.
The planned expansion will lead to an increase of 50% more pupils, bringing the total up from 60 to 90, providing council planners allow it.
The scheme will provide additional classrooms and an extra 53 car parking spaces would also be built.
But cabinet members will next week consider approving a revised business case for the project and a new cost of up to £6.141m.
Some of the costs relating to access arrangements to the part of the school being extended were higher than expected.
And builders will need to use the southern entrance which passes over the school field which will be more expensive they need a longer run of temporary roadway is needed.
The overall cost of the design stage will also have increased.
Ward councillor Paul Rone said the cost of construction projects do vary.
He said: “The cost has gone up by 25% but this is for the best junior school in the county to have an extra 90 pupils for the next 25 years.
“It will be interesting to see how much money is in the budget to spend on unforeseen circumstances.
“There is always a risk with these sorts of projects where you come across asbestos or contaminated land. This is obviously not the case in this instance.
“But construction costs do go up and it is not a surprise to me.”
The plans include a new extension comprising of six new classrooms and associated learning spaces, new staffroom facilities, a new hall, an improved and enlarged kitchen to produce hot meals onsite.
Cabinet will consider the revised business case and budget at Leominster Library at 6pm on November 27.