Applying sheet metal skin to a unit is more of a proprietary art that depends on the skills set of your team and capabilities of the equipment in your facility. The following pictures show common techniques used by fabricators throughout the industry.
The picture below shows the standard method of installing an inner flat sheet skin against the framing flange followed by insulation and the outer skin. This set up is particularly good for negative pressure applications because the pressure draws the inner skin into the gasket which creates a better seal. Also take note of the overlapping edges at the corner.
In the scenario below you can see the same external set up, hut the internal skin has been shifted to cover the inside of the frame for positive pressure applications. As pressure builds, the inner skin is pushed into the gasket creating a better seal.
When skinning floors or installing tread plate, the inner skin should be placed on top of the flange as shown below. May times caulk/silicone is applied in addition to gasket as an extra layer of protection from leakage especially in high pressure applications.
Roof caps should extend over any seams across the top of the unit and it is a good practice create a rain diversion bend at the bottom edge of the downward flange. Pay attention to the location of doors and access panels so you do not extend the roof cap to a point where it obstructs the function of those components. Standing seams are often used for larger roofs that require multiple sheets of metal.
What gasket should I use?
Modular Framing Systems sells 3/4in wide x 1/8in thick, closed cell neoprene foam gasket with an adhesive back (gasket tape). You can use any gasket that meets your project specs just be sure to consider the relationships between panel thickness, gasket thickness, and gasket compression.
