Overview
Without an architrave, the outside frame fixes to the surrounding wall. Measure the opening, then add the stated frame coverage. A projecting sill removes the bottom allowance because the shutter finishes on top of it.
Measuring Outside Mount for a Square-Set Window
For My Direct's square-set face-fit method, measure the opening in three places in each direction and use the smallest width and drop. Add 42 mm at each side: 84 mm to the width and 84 mm to the drop.
If a sill projects at the bottom, add only at the left, right and top: 84 mm to the width and 42 mm to the drop. The bottom finishes on the sill. These are frame coverage allowances, not factory deductions.
Measuring Outside Mount for a Window with a Sill
For a square-set opening with a projecting sill, measure three widths inside the opening and three drops from the sill top to the opening top. Use the smallest readings under My Direct's square-set method. Add 84 mm to the width and 42 mm to the drop for the left, right and top frame coverage only.
