A couple of thoughts – to your point, either of the two options will provide a suitable roofing solution for this building. There are complicating factors – the details as it were – most prominent of which will be the weather and temperature conditions at the time of installation. Every building needs to be dried in as quickly as possible to facilitate interior operations – this building is no different. The base roof system uses only a lightweight vapour retarder that is not sufficient to keep water out of the building. In order to ensure the interior of the building is kept dry, the bulk of the roof system – insulation layers and base ply of the roof membrane will need to be installed.
The large problem with installing the bulk of the roof system too early is that damage during construction will occur – water will inevitably infiltrate into the insulation layers and compromise the quality of the roof system. To your point, what would normally be a suitable roof system will become a non-suitable roof system with damage. The same roof system, installed without construction damage and questionable weather would be suitable – but under these conditions – the same system will be problematic.
I understand that ownership is very focused on the economics and frankly, just plain dollars. There are two major advantages with the alternate system. First, it is hot applied and because the vapour barrier of the system is robust – that vapour barrier will keep water out of the building during construction without any additional layers. This hot vapour barrier can be installed quickly, which will allow the building to be dried in quickly under even iffy weather conditions. The installation of a complete or almost complete roof system is much slower and requires good weather conditions.
Speed in getting the building dried in – equals faster progress on interior operations and saves money as a result. Enhancements to schedule conformance is an added bonus.
The second consideration is the roof system as an asset to the building. If ownership wants to sell the building, it is much more attractive – and financially beneficial, to be able to advertise a long term roof system with a 25 year warranty on the building as opposed to a roof system that has been damaged during construction, probably has had some leaks and is not as long term.
If on the other hand, ownership wishes to retain the building for the longer term, the presence of a long term roof on the building that will not require expensive refurbishing is a substantial financial benefit.
I understand the situation and the necessity of working with all parties. I will, during any discussions that I have with the persons involved, describe and represent the differences between the two systems – from a roofing point of view with consideration of the financial implications.
I just want to inform of the details and potentially less obvious considerations that might factor into decisions – just in case anyone asks. Also, to keep us on the same page – I want to do the best I can to ensure a successful project.