Assembling sheet metal ducts in situ

[Stephen Tashi]

TL;DR

Is there a technique for assembling rectangular sheet metal ducts inside a ceiling cavity - as opposed to assembling them on a table top or other ideal situation?

In a house there is (typical of many 1950's vintage houses in my area) a framed cavity above the ceiling of a hallway and below the roof joists. It held a sheet metal heating duct "trunk line". The old ducts were removed since they had rusted through after being used (in the summer) with an evaporative cooler.

I'd like to replace the old duct work with new ducts. Is there a way to install new rectangular rigid sheet metal ducts in the cavity without tearing off drywall? - i.e. to install it only having access to the new work from the attic? The standard method for joining rigid rectangular ducts shown on internet videos involves using "drive strips" and having ample access to all sides of the ducts. Is there a slip-on type of connection that can be used instead?

(Of course, using round flexible ducts or round sheet metal ducts is another possibility. But I'd prefer to have one rectangular trunk line about 28" by 8" in cross section instead of several smaller round lines. The cross section of the cavity is 37 1/2 inches wide by 11 7/8 inches tall.)

Edit: I see that "frames" and "slip joints" are used in the UK. (I'm in the USA.) http://www.ductstore.co.uk/acatalog/Help_on_rectangular_ducting.html Those methods look more modern and saner than the method most used in the USA.

In USA terminology, the method using "drive cleats" is also called a "slip-on" method, but it's certainly more complicated than "slip-on" connections in other contexts.

 

[Lnewqban]

I would use Flat S Locks on four sides of each connection and install some screws around for eliminating any longitudinal movement, then seal with mastic all around.