08/04
31068 Rev E
17
MHST36D INSTALLATION INSTRUCTIONS
Figure 12 - Ceiling/Attic Construction
9. Install the MH842 Ceiling/Roof Thimble
See Figures 12 & 13.
a.
Locate the point where the chimney will exit the
roof by plumbing down to the center of the
chimney. Lay out, cut and frame a 14-1/2 in. square
opening (measured on the horizontal) through the
ceiling and roof structure. See
Chapter 25 of the
Uniform Building Code
for roof framing details.
b.
The thimble must extend completely through the
roof structure shielding combustible materials.
Five location holes have been provided to allow
for a variety of ceiling/roof thicknesses. An MH841
Thimble Extension is required when the ceiling/
roof thickness exceeds 12-1/2 in. The extension
should overlap the thimble one inch.
c.
To attach the extension to the thimble, drill 1/8 in.
holes through the outer shield of the thimble using
the predrilled holes in the extension as guides.
Attach the extension to the thimble using the
screws provided with the extension.
d.
Install the thimble assembly and nail it securely
to the framing members.
e.
Center the flashing over the chimney and nail it to
the roof using the Stormguard
nails provided. Keep
gaps between the flashing plate and the roof to a
minimum.
f.
Caulk the flashing plate and roof junction as well
as the vertical seam on the flashing. All nail heads
must be caulked with a roofing sealant.
g.
Finish assembling the chimney, storm collar and
termination cap following the installation
instructions provided.
Note:
The closed end of
the thimble is positioned
towards the bottom.
Figure 13 - Installing an MH842 Roof Thimble and Flashing Kit
