8
Thimble
Site constructed for masonry chimney installation:
Components
• A minimum length of 12 inches [05mm] (longer for
thicker walls) of solid insulated factory-built chimney
length constructed to UL 103 Type HT 6 inch (152mm)
inside diameter. Chimney needs to extend a minimum of
2 inches (51mm) from the interior wall and a minimum of
1 inch (25mm) from the exterior wall.
• Wall spacer, trim collar and wall band to fit solid pack
chimney selected.
• Minimum 8 inch (20mm) diameter clay liner section (if
not already present in chimney) and refractory mortar.
Air Clearances
• Masonry chimney clearance must meet NFPA 211
minimum requirement of 2 inches (51mm) to sheet metal
supports and combustibles.
• Minimum of 1 inch (25mm) clearance around the chim-
ney connector.
• Top of wall opening is a minimum of 1-1/2 inches
(4mm) from ceiling or 4-1/2 inches (114mm) below mini-
mum clearance specified by chimney connector manu-
facturer. NFPA 211 minimum vertical clearance of 18
inches (457mm) from chimney connector and ceiling or
minimum recommended by chimney connector manufac-
turer.
Figure 6.1.
Instructions:
1. Open inside wall at proper height for the chimney con-
nector to entry the masonry chimney.
Figure 6.1.
2. Entry hole to masonry chimney must be lined with an 8
inch (20mm) minimum diameter clay liner, or equiva-lent,
secured with refractory mortar.
3. Construct a 17 inch x 17 inch (42mm x 42mm) out-
side dimension frame from 2 x 2 framing lumber to fit
into wall opening. Inside opening of frame should be no
less than 14 inch x 14 inch (56mm x 56mm).
Figure 6.1.
4. Attach the wall spacer to the chimney side of the
frame.
5. Nail the frame into the wall opening. The spacer
should be on the chimney side.
6. Insert the section of the solid insulated chimney into
the outer wall of the masonry chimney.
7. Tightly secure the length of the solid insulated chimney
with the wall band to the masonry chimney.
8. Insert a section of chimney connector into the chim-
ney. Make sure it does not protrude past the edge of the
clay chimney liner inside the chimney.
9. Seal the end of the chimney connector to the clay liner
with refractory mortar.
10. Install trim collar around the sold pack chimney section.
Figure 6.1
Solid Pack Chimney with Metal Supports as a Thimble
Figure 7.1
WARNINg
Fire Risk.
Do NOT pack insulation or other combustibles
between spacers.
• ALWAYS maintain specified clearances around
venting and spacers.
• Install spacers as specified.
Failure to keep insulation or other material away
from vent pipe may cause fire.
