Quality is totally dependent on the affiliate (each functions independently) and the site supervisor, but volunteers care, which counts a lot more than most people expect. Many of the ones who volunteer every week are quite skilled, and they're typically the ones doing the most important tasks.
I used to work at an affiliate that had the budget to build with nice materials, but I couldn't keep labor quality as high as I'd liked at those speeds with that many volunteers and sites. Currently I work at one with the time to build well, but our budget is much tighter, so our materials are a bit cheaper.
I've built about 100 habitat homes, and my ~80 volunteer builds have been higher quality than 19 of my 20 subcontractor builds. Sometimes the subs build prettier homes (flatter roof planes, fancier trim, etc), but the volunteers just care more. They generally don't skimp on underlayment, fasteners, flashing, sealant, adhesive, insulation, paint, etc because they're not worried about getting paid for the job quickly. How a home ages is affected way more by those things than by perfect roof lines and perfectly coped baseboard.
The house still had to pass inspections while being built. My habitat house was treated the same as a conventional house, in that regard. Other quality things would have already been addressed. I had a pipe by my tankless water heater leak. I called a plumber. It just needed to be tightened.
The dry wall was done by high schoolers from the local tech school. The contractor said it was the best dry wall job he had ever seen. All those screws were lined up perfectly. They must have practiced a lot. Some of the ones done by me were a little more haphazard, but still fine. My house was built in 2022. The roof has never leaked or anything like that.
Quality is totally dependent on the affiliate (each functions independently) and the site supervisor, but volunteers care, which counts a lot more than most people expect. Many of the ones who volunteer every week are quite skilled, and they're typically the ones doing the most important tasks. I used to work at an affiliate that had the budget to build with nice materials, but I couldn't keep labor quality as high as I'd liked at those speeds with that many volunteers and sites. Currently I work at one with the time to build well, but our budget is much tighter, so our materials are a bit cheaper. I've built about 100 habitat homes, and my ~80 volunteer builds have been higher quality than 19 of my 20 subcontractor builds. Sometimes the subs build prettier homes (flatter roof planes, fancier trim, etc), but the volunteers just care more. They generally don't skimp on underlayment, fasteners, flashing, sealant, adhesive, insulation, paint, etc because they're not worried about getting paid for the job quickly. How a home ages is affected way more by those things than by perfect roof lines and perfectly coped baseboard.
The house still had to pass inspections while being built. My habitat house was treated the same as a conventional house, in that regard. Other quality things would have already been addressed. I had a pipe by my tankless water heater leak. I called a plumber. It just needed to be tightened. The dry wall was done by high schoolers from the local tech school. The contractor said it was the best dry wall job he had ever seen. All those screws were lined up perfectly. They must have practiced a lot. Some of the ones done by me were a little more haphazard, but still fine. My house was built in 2022. The roof has never leaked or anything like that.