The majority of British architecture practices are experiencing on-site delays caused by difficulties in sourcing construction products according to RIBA's Future Trends survey.
A quarter of practices have seen site work put on hold due to a lack of materials.
The materials shortage is reportedly due to the impact of Brexit, as well as an increased demand for materials, as construction starts to ramp up again with the easing of coronavirus lockdowns.
"It has been mentioned by practices over the last couple of months, but it's picked up as one of the main issues over the last few weeks," head of economic research and analysis at RIBA Adrian Malleson told Dezeen.
The industry is also still feeling the impact of the Suez blockage, RIBA said.
Construction and design stages affected by material shortages
Nearly a fifth of practices, 18 per cent, also reported that the materials shortage was creating delay in the design process.
"Talking to practices, the delays are occurring in the detailed design stages as practices have to spend additional time selecting products that will be delivered within project timescales, where that's possible," Malleson said.
RIBA said reports of other significant challenges for architects include labour shortages and the potential effects of the "gathering third wave and the planned lifting of Covid-19 restrictions".
Brexit is also affecting other areas of the industry.
"The UK is experiencing workforce shortages within important areas, such as distribution (especially HGV drivers) and among builders merchants; though this is also linked to Brexit," Malleson added.
Majority of practices expecting workloads to remain the same or increase
However, the survey noted optimism in relation to future work, with 38 per cent of practices expecting to have more work in the next months.
Just over half, 58 per cent, expect workloads to stay the same, while the percentage expecting a decrease fell to seven per cent.
This indicates that the recovery is continuing, RIBA said.
"Overall, the June Future Trends findings indicate that the recovery in the architecture market continues," Malleson said.
A total of 240 practices, based on a representative sample of the range of different practice sizes and geographical locations, took part in the survey in June.
French architects have also reported issues of materials shortage, with wood prices increasing weekly due to a new law that requires public buildings to be 50 per cent wood. The issue is said to mainly concern structural timber.
In Sweden, the construction industry is anticipating a shortfall in concrete as the country's largest cement factory was stripped of its license on environmental grounds.
The Cementa factory in Gotland could be forced to end production in November, which construction bodies claim could lead to stoppages on three-quarters of all house-building projects.