New build submissions nearly doubled in September, adding fresh pressure just as approval rates had improved and older cases were being cleared.
Schemes covering more than 40,000 homes now await decisions, with new build applications arriving twice as fast as BSR is determining them.
The regulator has activated contingency plans to handle the surge and protect projects already in the queue from further delays.
September brought 64 new build submissions, up from 34 in August and 17 in July, ahead of the levy taking effect on 1 October.
The overall Gateway 2 caseload grew by 34 during the month to 1,706 applications, including 186 new build and conversion cases.
BSR said: “We will engage with applicants on an individual basis to discuss timelines for their projects.”
The regulator has added 25 staff to its internal regulatory team over four months and plans further recruitment over the next six to 12 months.
It is also expanding specialist teams, with integrated building inspector capacity forecast to rise from 22.4 full-time equivalent posts at the end of September to 34 in December.
The mounting workload comes despite BSR approving 55 of its 57 new build decisions over the latest 12 weeks.
Median approval time edged up from 22 weeks to 23 weeks over the month, which the regulator attributed to clearing older cases.
Complex applications are tracked separately, with a median approval time of 34 weeks.
Internal refurbishment remains the biggest pressure point by volume, accounting for 1,109 live applications. Additional processing capacity is due in the coming months.
There is better news on external remediation, where decisions outpaced new applications. Just seven cases from 2024 remain, down from 42 at the start of the year.
BSR has also introduced extra scrutiny before invalidating or rejecting applications, recognising the potential impact on project viability.
It said: “We will only reject applications where there is no realistic prospect of approval within a reasonable timeframe.”
Meanwhile, Gateway 3 is emerging as another capacity challenge. Just nine applications were determined over the latest 12 weeks, taking a median 20 weeks.
No new build scheme that passed through Gateway 2 has yet reached that stage. BSR said it expects new processes and additional resources to bring determination times down.
