Why do most replacement companies use only the block frame methodology? Profit. It is more than twice as fast to do a block frame install as a certified install. Since the majority of us don’t know the difference, and most replacement company’s subcontractors are paid on a piece rate for each window installed, this corner is routinely cut.
Often times the block frame approach is sold under the guise of saving you money – “we will not disturb your exterior trim so we won’t have to charge you for materials and you won’t have the hassle of repainting!”
In the case of stucco exteriors, doing the install right is substantially more expensive than the block frame approach as it is very difficult to patch stucco to the same appearance as the surrounding wall after the original stucco was cut back to allow for a certified installation.
How to tell which installation methodology was performed? If your window is in brick or stone, it was a block frame install as there is no opportunity to use the nailing fin or flashing. If not, examine the caulk around the windows that receive the greatest sun exposure, usually the west or south elevation. If the caulk is separating from the window, you can insert the blade of a knife or an awl into the gap. If you don’t hit a solid surface, the nailing fin under the flashing, within an inch to an inch and a half, you have a block frame installation.
What can you do about a block frame installation after the fact? It is imperative that the caulk be maintained gap-free. Even if gaps have opened up, re-caulking and subsequent diligent maintenance should minimize any damage and maximize the longevity of the install.