If you have a simple rectangular floorplan with no additions or porches just add up 2x the length of your home and 2x the width of your home.
How to stop mobile home siding from leaking.
The rigid head flashing must be sealed to the exterior sheathing and to the top of the exterior casing fig.
Use a caulking gun to apply a continuous bead of silicone sealant along the vertical seams between the vinyl j channels and the exterior window casings.
Inspect the area above the leak including both indoors and out.
This will cover all the areas that need skirting.
Do not nail any part of this assembly to the roof.
How to stop rainwater from running behind house siding originally published november 29 2008 at 12 00 am gutter leaks can do hidden damage when siding masks the problem.
Also see peel stick flashing membranes.
Check to be sure weep holes are open along bottom of window openings.
Vinyl siding institute cited below.
Cut a notch on the ends of the rigid head flashing and bend them down over the sides of the exterior casing.
Sandwich the top end of the sheeting with another pair of 2 by 4s so the wind will not carry it away.
First you need to measure the linear footage of your home.
In most communities building codes require a moisture barrier.