The need to provide toilets for workers revamping Thickthorn roundabout could stop or delay the building of new homes.
National Highways is seeking a 'development consent order' for multi-million pound major changes to the junction, on the edge of Norwich.
But Big Sky Developments, owned by South Norfolk Council, is building 350 homes at Cringleford, next to the A11 and A47.
And a 2023/24 phase in the St Giles Park development includes building three houses near Cantley Lane, where an underpass would be created, if the Thickthorn changes are approved.
But, if National Highways does get permission, it would need to provide somewhere for workers to go to the lavatory while they work on the revamp.
And the agency wants to temporarily acquire 1.7 acres of Big Sky's land, earmarked for the three homes, to provide a workers' welfare facility, including toilets and rest areas.
Construction of the Thickthorn scheme would coincide with when the homes are due to be built.
The issue was raised at Wednesday's (March 2) Planning Inspectorate hearing into the scheme, where Big Sky urged National Highways to find an alternative site for the welfare facility.
Charles Birch, from Norwich-based Brown & Co, on behalf of Big Sky, said: "We are not trying to pick a fight with them. We would just like them to be imaginative and find somewhere else to go."
He said Big Sky might be able to offer another space on land the council owns, although that would be outside the "red line" the development consent order application covers.
Ben Williams, for National Highways, said different options had previously been explored and Big Sky's offer would need to be discussed outside of the hearings.
The changes would also see a segregated left-hand turn added to those travelling eastbound on the A47, a new footbridge and a fourth lane on the southern part of the junction.
Once hearings end, the planning inspector will make a recommendation to transport secretary Grant Shapps, who will decide whether the scheme goes ahead.
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