Alternate wood frame method
Where  poured header, with curved inner surface, is not
provided, a wooden section is built within the rectangular
opening, having a curved surface to which the window
buck is mounted. This method is often used to 
match CMU walls with wood frame walls. 
Because bending a wood buck is difficult, this method is
better suited to flush mount, finned windows.
Window Fitters Guide to Window Installation 
133               ©2022 AWDI, LLC Do not reproduce without permission
Seal Joint
Wood Constructed 
Header Opening
with arched wood
blocks
Kerfed Curved
“Buck”
Smoothly Arched
Cellular PVC
Header Buck
Kerfing - cutting multi
grooves in wood to
facilitate bending
Free Foam Cellular 
pvc can be arched
smoothly to make the
best curved buck
Once a curved masonry 
header member is created, 
the installation steps are 
basically the same as for 
rectangular windows
Cellular PVC “arched”
Header buck
It is difficult to 
kerf wood which
often creates a poor 
header buck
Blocks are fastened
in a rough arc to
which the kerfed
buck is to be nailed
SAMPLE MANUAL

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