We've recently moved into a new-build (completed in May 2023) and been made aware of an issue with the DPC and the air bricks to the rear of the house (with bi-fold doors opening to a patio). Both DPC (above the air bricks) and air bricks are below the ground level and covered by gravel (see image attached).
We talked to the developer who said that they are below the ground level because the patio has to have a level threshold. To allow sufficient ventilation, the developer suggested to cut back the patio 150mm from the rear house wall on both sides of the bi-fold doors, dig out below the air bricks and then fill the bottom of the trench with gravel so that the top of the air bricks will be 150mm above the gravel.
I am not happy with the proposal by the developer, because 1) I am not sure if 150mm wide trench is sufficient, as NHBC Technical Guidance says "air bricks below general ground level are acceptable with continuous strip of lowered ground extending at least 600mm away from front of air brick(s)". and 2) The proposal didn't solve the issue that the DPC below the bifold doors are still below ground level. The Building Regulations about a level threshold and the DPC being 150mm above ground level seem to contradict with each other.
Could anyone advise what is the best solution to fix this issue and whether it would impact the value of the house?
(On a related note, the house passed Building Control during construction. I emailed Building Control, who basically admitted that they didn't check air bricks at all. I wonder if I could do anything about it).
All suggestions are highly appreciated. Many thanks!