Keller W2200 Serie Instrucciones De Instalación página 13

Section 1.5 (continued)
CUTTING THE CEILING JOISTS
STEP 4. Determine where the joist(s) should
be cut. Figure 10 shows where to mark
the joist(s) that span your chosen
location. Note that the joist(s) should be
marked back from the edge of your
location a distance of 2 times the joist
thickness (usually three inches).
This leaves room for two joist-sized
headers to be placed against each end
of the cut joist(s) (See Figure 16 on
page 15).
Note: In some homes, especially older
ones, the joists may be slightly thicker
than the lumber you can currently buy.
If your joists have a different thickness than
the lumber you will be using for the headers,
you will need to mark the joists back from
the edge of your location a distance of two
times the header thickness instead of the
joist thickness.
STEP 5. Saw through the joist(s) being careful not to
cut through the ceiling and making sure the
cut ends of the joist(s) are flat and vertical.
Section 1.6
FRAMING THE ROUGH OPENING
Before Proceeding: You should have a space between the joists at least as large as the rough
opening shown on the box. Any cut joists must be attached to uncut joists.
Goal: To create a four-sided frame the size of the rough opening using joist-sized lumber. This
frame will be made of single or double thickness headers and stringers depending upon the par-
ticular installation. The frame is necessary to support the attic ladder and to reinforce the roof and
ceiling structure.
Do not stand or sit on the ceiling or insulation covering the ceiling — the ceiling is not made to
support your weight. You can fall through the ceiling even though it looks solid! Only the joists
can support weight. To avoid falling through the ceiling, you may want to make a working
platform by laying boards across the joist. Watch out for sharp nails sticking through the roof.
WARNING
For your safety, watch out for overhead hazards.
2x joist
thickness
Dotted line indicates
your chosen location
FIGURE 10
Cut Here
Section of joist to
be removed
Cut Here
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