Monessen Hearth M400BFC User Manual

7

Preplanning an installation is very important to ensure 
safety and to save time and money.  An installer must 
predetermine where a fireplace will be set and how the 
chimney system will be run.

A fireplace may only be mounted on the following sur-
faces:
1.  A flat combustible surface.
2.  A raised wooden platform.
3.  A concrete block or other solid object placed be-

neath each of the four (4) corners of the fireplace.

The fireplace must be spaced 1” (25 mm) from a com-
bustible back wall and 1/2” (13 mm) from a combustible 
side wall or support. (Page 13, Fig. 17)

Determine how the chimney will be run, length of run 
and chimney components required to complete the 
job. (Fig. 4)  Never install a chimney below minimum 
heights.

In planning a chimney system, it is important to know:
1.  The height of a chimney is measured from the 

hearth to the exit point on the termination.

2.  A chimney cannot be offset more than 30° from a 

vertical plane.

3.  A chimney may run straight up or it may be neces-

sary to offset it to avoid obstructions.

4.  The maximum length of an angled run (total chimney 

system) is 20’ (6 m).  

5.  No more than 2 offsets (4 total 30° elbows in U.S./or 

2 total 45° elbows in Canada) per fireplace may be 
used.

6.  A guy wire stabilizer is required for chimneys extend-

ing more than 6’ (1.8 m) above a roof line.

Major U.S. building codes specify a minimum chimney 
height above the roof top. The “Ten Foot Rule” is a fire 
safety rule and not a draft rule.  To ensure proper draft, 
it is recommended that you always meet or exceed the 
“Ten Foot Rule,” especially when installing a termination 
on a high pitch roof.  (Fig. 5)
The key points of the “Ten Foot Rule” are:
1. If the horizontal distance from the chimney to the 

peak of the roof is 10’ (3 m) or less, the top of the 
chimney must be at least 2’ (610 mm) above the 
peak of the roof, but never less than 3’ (914 mm) 
in height above the highest point where it passes 
through the roof.

2. If a horizontal distance from the chimney to the peak 

of the roof is more than 10’ (3 m), a chimney height 
reference point is established on the surface of the 
roof a distance of 10’ (3 m) from the chimney in a 
horizontal plane. The top of the chimney must be 
at least 2’ (610 mm) above the reference point, but 
never less than 3’ (914 mm) in height above the high-
est point where it passes through the roof.

L1

L1

LT

56O

56O

56O

56O

56O

56O

56O

56O

FP288A

MBUF-INSTALLED LENGTH

Triple wall

1/28/99   djt

81

818

83

84

FP288a

Fig. 4  Installed lengths of chimney sections.

2’ Min.

2’ Min.

3’

Min.

0 To 10’

3’

Min.

0 To 10’

AC246

4/1/96

Reference

Point

AC246

Fig. 5  Ten Foot Rule illustration.