This is complex and involved major piece of work that has to be done correctly and certified. There is absolutely no point in going to a contractor without having a clear set of specs and plans in place. The answers you will get will be worthless, and likely cost you many times what you think it will cost.

The work involved covers: parapets, caps & copings, drainage, masonry, pre-cast sills, lintels, facade cracks, cutting & caulking, Terra-Cotta repair and sealing work. This can include, as in our building, the fact that the original mounting straps holding the T-C to the facade were pulling away from the building, necessitating an expensive and carefully engineered process and design solution for dismantling, replacing corroded straps with new SS straps, and re-installation. Then there are the fire-escapes, windows and sealants, roof inspection, elevator head/housing, gutters, pointing and ironwork.

There are architects and Engineers who both specialize in this work. They will have to do a very close inspection, photograph everything, and draw up detailed plans, devise the exact specs on how it will be dealt with, the products to be used, especially if they have to replace bricks and mortar that needs to match, and be knowledgeable in how a building constructed at the time yours was, was actually built.

There are three phases to the Architect's job: P1 - the site inspection and the specification work, the analysis and design documentation and technical drawings, bid documents and refereeing the site surveys by bidding contractors (on-site scheduled meetings) bid review, and advisement on selection and negotiations. P-2 is: the on-site inspection of the work being done by the contractor (how many visits you will require them to make for each significant type of work) and any additional on-site discoveries and solutions, or for that matter the Architect requiring them to redo work they have completed as insufficient, improperly executed, etc. not extensive enough, or the Contractor finding things and going to the Architect and saying you missed this, or we have found hidden damage you could not have foreseen etc. (they need to work well together). You need the Architect o see and approve all replacement bricks and mortar to ensure a proper match). The end of this phase is the Architect's sign-off on the Contractor's job. P-3 is: the Architect's final report and inspection notes, certification and stamps to the DOB and their inspection, with the Architect of the job.

You will probably have to put up a bridge on the street side of your building. That is expensive, so do everything you need to and do everything preventative as well. Spend the money once. P1 - a couple of years back ran us $15K, P2, $4,500, and P3 $2.5K, the bride alone was $20-25K on a 6 story street side facade (rest of building is 7 stories/30 units. facade work ran us about $135K We had to do this twice in a 5 year period because of storm damage. Without a plan in hand, the variables that Contractors will tell you are huge, when you compare bids it is startling how the prices for similar items will vary, based on their own resources and way of doing the same job. Bid five+ in the hopes that you get back 3 usable bids. Insist that everything be line itemized, and that materials and labor be broken out separately and itemized. Retain the exclusive right to amend the RFQ so you can drop/add/modify sections or elements after receiving bids to make it affordable. We dropped out almost $40K in pre-cast custom sill replacements and substituted caulking all around and of any sill cracks thereby replacing only 5 of over 140+ sills. If you do not have a qualified building management construction person to Supervise the job from your end, then you will have to do it, overseeing the Architect. Do not allow your Management company to just supply you with a contractor, DO the work, interview architects and Engineers, interview Contractors with the Selected Architect/Engineer. This is a ferociously expensive project that can quickly go out of control, AND if not done correctly, can have you doing it over in less than five years at greater expense. A good architect and a good contractor will help you, will find ways to save you money and working together do it better, safer, and a hopefully more durable job. I would say we have been lucky, but we have good Management, and we made our own luck thru diligence.

I am sure I must have left somethings out, but this is the general idea, anyway.

As to windows and doors, and who is responsible. That will be in your proprietary lease, Bylaws etc. (I am Coop oriented), regardless of how it falls out, you do not want individual owners replacing windows with whatever they want, in whatever color they want, and whatever quality they feel like, You need to set up a building wide plan for replacements, pick you price point, color and style and stick firmly to it, and asses them all accordingly. You do want to hire an Architect to consult as it can be complicated as to choice and needs.

There is no viable shortcut around using experts. Whether it be Architects and Engineers, CPA's, Certiorari work or licensed tradesmen.

It will always save you either money, grief or both. These are big ticket projects, requiring permits and DOB filings. You don't want the supplier acting as his own supervisor, really! You don't need a big fancy architect or Engineering firm. You can do with a small practice office with really smart and skilled people. IT can be a solo outfit. Just do your homework, knock on doors, if you see a job being done, ask questions, find out if everyone is happy with the execution of the job. Drive around the neighborhood, Check habitat articles for Vendors who did well, and who to avoid, there are plenty of those around!
To do it right is a lot of work, to do it wrong is even more work,
Good luck.