Checkatrade gives £800-£900 for a standard timber stud wall 3m long and 2.4m high. A separate UK guide puts a softwood internal door supplied and fitted at £125-£350. Use the two figures to start the conversation. A new doorway also needs a framed opening and lining, and your builder should say which items the wall price already covers. The guides leave the VAT basis unspecified. Partition costs · Door costs.

Draw the two finished rooms

A 3m wall can split a long room into a study and sitting room, but the door position determines where a desk or sofa will fit. Mark the wall and door swing on the floor. Walk from the entrance to the window and check the route past the furniture. Try the door opening the other way before deciding.

On the drawing, mark any socket, light switch or radiator that ends up on the wrong side. If someone will take calls in the new study, tell the builder. The boards, insulation, door and gaps around it all influence how much sound travels between the rooms.

What should the door allowance buy?

Agree the door type, hinges, latch, handles, lining and architraves on both sides. Include the skirting where it meets the new wall. If the carpet runs continuously beneath the partition, ask the fitter how each edge will finish and what will be visible at the threshold.

Changing a layout can affect escape routes and ventilation. Check which Building Regulations requirements apply before settling the layout, especially when creating a bedroom. Planning Portal explains the checks.

For a house refurbishment, agree the boards, doorway and plaster finish in one description so each quotation prices the same result.