Friday, December 10, 2010

Porch Ceilings, Soffit, Fascia

Requirements for Proper Soffit Ventilation
Proper attic ventilation is important for any home. The 2003
International Building Code (IBC) Section 1203 Ventilation
furnishes a basic guide for determining proper ventilation for
any home. The information provided here may under certain
circumstances not result in enough ventilation. Therefore, the
calculation provided should be used as a guide only.

The IBC guideline requires that any attic or space between the top
floor, ceiling and roof must be ventilated. It requires one square
foot of ventilation area for every 150 square feet of attic space.
If a vapor retarder of less than one perm has been installed on
the warm side of the ceiling or if at least 50% of the required
ventilating area has already been provided by gable and vents
or ridge vents, you need add only one-half of the ventilation
area that would otherwise be required. The requirement would
then be one square foot of ventilation area for every 300 sq. ft.
of attic space.

How to Determine Soffit Ventilation
1. Determine the local code requirement for total attic
ventilation.
1:150 requires 1 sq. ft. of ventilation for every 150 sq. ft. of
attic space.
1:300 requires 1 sq. ft. of ventilation for every 300 sq. ft. of
attic space, if a vapor barrier having a transmission rate not
exceeding 1 perm is installed on the warm side of the ceiling.
2. Determine the total area of the attic (sq. ft.) to be
ventilated.
40 ft. x 30 ft. = 1,200 sq. ft.
3. Total free area of ventilation required for the attic.
1,200 sq. ft. / 150 = 8.0 sq. ft.
4. Convert square feet into square inches (sq. in.).
8.0 sq. ft. x 144 = 1,152 sq. in.
5. Location of vents.
50% at ridge, roof vent or gable vent = 1,152 x .50 = 576 sq. in.
50% at soffit / eave = 1,152 x .50 = 576 sq. in.
6. Total soffit ventilation area required.
Area of the soffit available for ventilation:
80 lineal ft. x 2 ft. soffit depth = 160 sq. ft.
Ventilation area required per sq. ft. of soffit =
576 sq. in. /160 sq. ft. = 3.6 sq. in /sq. ft.
7. Soffit product selection.
Compare the soffit ventilation area required to the
manufacturer’s soffit product literature.
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CertainTeed Vinyl Siding Installation Guide
SECTION 7 – Porch Ceilings, Soffit, Fascia
40'-0"
2'-0"
2'-0"
30'-0"
ridge eave
Porch Ceilings
The procedures used to install a porch ceiling are in many
ways similar to those used to install soffit. These procedures
vary slightly, depending on whether you’re working on new
construction or a remodeling project.
New Construction Projects
Begin by installing receiving channels on all four sides of the
porch. If you are using F-channel, nail it to existing walls. If you
are using J-channels, you will have to install a nailing base.
If you plan to use light blocks to attach external light fixtures,
install them to adequate backing.
Plan the layout of the ceiling panels to achieve an even
balance or to align with adjacent work. If the ceiling panels will
run parallel to the ceiling joists, you will have to install
additional 1 x 3 wood furring nailing strips. Install these nailing
strips perpendicular to the ceiling joists, placing a strip every
12" to 16".
Invert J-channels and nail them to the underside of the wood
strips along the perimeter of the ceiling area.
Install the first panel into the channels at one end of the porch.
Be sure to leave room for expansion. Nail every 12" to 16",
positioning the nails in the centers of slots. Do not nail tightly.
Install remaining panels. When cutting the last panel of the
first course, be sure to allow room for expansion.
For areas where more than one panel length is needed, use a
double channel lineal.
If necessary, rip cut the final panel and use a snap lock punch
to create tabs every 8" to 10" along the cut edge. Attach utility
trim and insert panel into the receiving channel.
NOTE: For best results, ensure you have adequate
ventilation.
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CertainTeed Vinyl Siding Installation Guide
Remodeling Projects
Check to be sure the existing ceiling can serve as a solid
nailing base. If the existing ceiling is solid, remove all existing
moldings and fixtures from the ceiling and begin by nailing
inverted J-channels along the perimeter of the ceiling area.
If you plan to use light blocks to attach external light fixtures,
install them to adequate backing.
Plan the layout of the ceiling panels to achieve an even
balance or to align with adjacent work.
Use the existing ceiling as a nailing base for the panels. Install
the first panel into the channels at one end of the porch. Be
sure to leave room for expansion. Nail every 12" to 16",
positioning the nails in the centers of slots. Do not nail tightly.
Install the remaining panels. When cutting the last panel of the
first course, be sure to allow room for expansion.
For areas where more than one panel length is needed, use a
double channel lineal.
If necessary, rip cut the final panel and use a snap lock punch
to create tabs every 8" to 10" along the cut edge. Attach utility
trim and insert the panel into the receiving channel.
If the existing ceiling is not solid, install nailing strips to provide
a secure nailing base. Then install J-channels. You will have to
install additional nailing strips if your ceiling panels are to run
parallel to the ceiling joists.
If the ceiling panels will run parallel to the ceiling joists, you will
have to install additional 1 x 3 wood furring nailing strips.
Install these nailing strips perpendicular to the ceiling joists,
placing a strip every 12" to 16".
Invert J-channels and nail them to the underside of wood
strips along the perimeter of the ceiling area.
Install the panels as explained above.
CertainTeed Vinyl Siding Installation Guide
77
Soffit
You can use solid vinyl panels or perforated vinyl panels for
soffit installations. Perforated panels provide ventilation, which
helps to reduce heat buildup in the summer and ice dams in
the winter. In buildings with roof ridge vents, you should install
ventilated soffit. Check local building codes to determine the
amount of ventilation required. In high windload areas, you
should also check local building codes to determine if the
application methods that are required differ from those
described below.
The procedure used to install soffit depends on the
construction of the eaves:
• Open eaves—eaves with exposed rafters or trusses—are
typical of new construction. You will also have to use open
eave installation procedures if you have to remove damaged
soffit at a remodeling project.
• Enclosed eaves—eaves with soffit in place—
are typical of remodeling projects.
Installation over Open Eaves
The first step in installing soffit is to install the proper receiving
channels. You have several options for receiving channels. You
can use accessories such as F-channel or J-channel, or you
can make channels using coil stock. The best approach is to
select a method that works most effectively with the
construction techniques used to create the eave. Examine
figures 1-4 and find the one that most closely resembles the
construction methods used on your particular project.
If no F-channel is available, J-channel can be modified to
create F-channel. Simply cut slots in the nail flange area where
it would be nailed to the wall. After cutting the nail flange,
bend the flange back and nail to the wall. When installing
Beaded T2" panels, use 3/8" H-bar or 3/8" J-channel.
Installing Receiving Channels
Install the receiving channels following the details shown in
figures 1-4. Nail the channels every 16", positioning the nail in
the center of the slot. Do not nail tightly.
If the eave span is greater than 16", you will have to install
nailing strips (as shown in figure 4) and install the receiving
channels on the nailing strips.
If the soffit will turn a corner, cut and install the channel so there
is 1/4" for expansion at each of the adjoining walls.
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CertainTeed Vinyl Siding Installation Guide
fascia cap or
coil stock
fascia cap or
coil stock
open truss
F-channel
soffit
16"-24"*
open truss
F-channel
J-channel
soffit
16"-24"*
open
rafter
F-channel
J-channel
soffit
soffit
add nailing
strips
add
framing
16"-24"*
16"-24"*
FIGURE 2
FIGURE 1
FIGURE 4
FIGURE 3
* To determine the maximum permissible span, consult
individual product specifications and local building codes.
Installing Soffit
Measure from the wall to the fascia board. Then subtract 1/2"
to allow for expansion. Mark this dimension on a soffit panel
and cross cut the panel using a power circular saw with a
reversed fine-tooth blade. Cut one or two panels at a time,
carefully advancing the saw through the vinyl.
Insert the panel into the channel on the wall, then into the
channel at the fascia board. You may have to flex the panel
slightly to insert it into the second channel. Make certain the
panel is perpendicular to the wall, then nail. Depending on the
installation method you’re using, you’ll nail either to a nailing
strip or to the fascia board.
Nailing Schedule for Soffit
Beaded T2" Fasten every 8" to 12"
Ironmax Fasten every 16" to 24"
(as allowed by local building code)
T3-1/3" Fasten every 16" to 24"
(as allowed by local building code)
All other CertainTeed
soffit panels Fasten every 16"
If you’re nailing to the fascia board, use small-headed nails.
Drive the nail through the nail flange and “V” groove. This is
one of the rare instances when face nailing is permissible.
Once a soffit panel is face-nailed, it will expand only in one
direction—in this case, toward the receiving channel. Be sure
to leave space for the full expansion allowance in the receiving
channel.
If you’re using a nailing strip, do not nail tightly—allow
movement for expansion.
Continue installing the panels by locking and nailing the soffit
in place. Make certain soffit panels are fully locked along their
entire length.
Turning a Corner
To turn a corner, measure from the channel at the wall corner
to the channel at the corner of the fascia board. Subtract 1/4"
for expansion. If necessary, install nailing strips to provide
backing for the lineal. Cut and install soffit double channel
lineal or H-bar. Miter the corner soffit panels and install as
described above.
Completing the Installation
To complete the installation, apply utility trim and fasten
aluminum fascia cap or formed aluminum coil stock with
painted trim nails. If you must face nail fascia, drill holes for
the trim nails to allow for expansion and to reduce denting of
the aluminum.
CertainTeed Vinyl Siding Installation Guide
79
fascia
soffit
panels
bent
aluminum
coil stock
nail into slot
nail into “v”
soffit
H-bar fascia
miter soffit
panels
Installation over Enclosed Eaves
If the existing soffit is rotted or damaged, it’s best to remove
it completely before installing vinyl soffit. Then use the
instructions for open eaves.
If you’re installing perforated soffit panels and the existing
soffit doesn’t have openings for ventilation, cut an adequate
number of openings. Then complete the installation as
described for open eaves.
The procedure used to install soffit over an enclosed eave is
almost identical to that used for an open eave. The major
difference is the installation of the J-channel. Determine the
method you’ll use to install soffit at the fascia board (see
figures 5 and 6). When installing J-channel at either the wall
or the fascia board, nail the J-Channel every 12"-16".
Turning a Corner
If the soffit is to turn a corner, cut and install J-channel so
there is 1/4" for expansion at each of the adjoining walls and
adjoining fascia boards. Miter the corner soffit panels and
install as described above.
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CertainTeed Vinyl Siding Installation Guide
fascia cap or
coil stock
nailing
strip
J-channel
soffit
enclosed
eave
J-channel
enclosed soffit
eave
FIGURE 6
FIGURE 5
Triple 3-1/3" Solid and InvisiVent Soffit
Installation over open eaves
In most situations, T3-1/3" Solid and InvisiVent Soffit should be
installed like our standard soffit products. However, when it is
installed over open eaves, follow these installation techniques.
Install receiving channels
There are two ways to install receiving channels for soffit. The
best approach is to select a method that works most effectively
with the construction techniques used to create the eave.
Examine the illustrations, and find the one that most closely
resembles the construction methods on your particular project.
Use either 3/4" J-channel or 3/4" F-channel, or make receiving
channels using coil stock.
Install the receiving channels following the details shown in the
illustrations.
Nail the channels every 12" to 16", positioning the nail in the
center of the slot. Do not nail tightly.
NOTE: If you are concerned about excessive insect
infiltration with the InvisiVent Soffit, cover the opening
with corrosion-resistant mesh or other screening before
installing the soffit.
Install soffit
Nail the soffit every 16" or 24", depending upon local building
codes and stud spacing. T3-1/3" soffit will span up to 24"
without additional nailing strips.
Installation over existing soffit
When installing InvisiVent Soffit over an existing solid wood
soffit, you must cut openings into the existing soffit to provide
adequate airflow through the soffit. The goal is to have at least
9 square inches of net free air per lineal foot of soffit.
Removing a center portion of the existing soffit will provide the
desired airflow.
Using a saw, cut along the length of the existing soffit. Leave
2" to 3" from both the wall and the fascia so that you will have
enough wood surface to securely fasten the soffit.
Remove the center portion of the existing soffit.
Install the soffit as described above.
CertainTeed Vinyl Siding Installation Guide
81
fascia cap or
coil stock open
rafter
F-channel
soffit
add framing
J-channel
soffit
Fascia
The wooden fascia board that encloses the front of an eave
also needs protection from the weather. To provide this
protection, you can install vinyl or aluminum fascia panels.
There are two procedures for installing vinyl fascia panels—
one for installations that include soffit, one for installations
without soffit.
Installations without soffit
Nail undersill trim in place along the top of the fascia board.
Before installing the panel, create tabs along the top edge
using a snap lock punch.
Hook the bottom of the fascia panel under the bottom of the
fascia board. Push the top edge into the undersill trim, as
shown, or behind drip edge.
Secure the panel to the bottom of the fascia board with white
trim nails. Fasten at nail slot openings only (see illustration).
Do not face nail fascia panel.
When overlapping fascia panels, first cut a notch in the
underlying panel. The notch should be 1/8" deep by
1-1/2" long. Slip the notched panel into the adjacent
panel (see illustration).
To turn a corner, you must first fabricate a corner piece.
Cut a length of fascia panel so it extends 6" beyond the
corner. Mark a vertical line to indicate the position of the
corner. Then cut a 90° V-notch centered on the vertical line.
Score it along the vertical line and fold. Finally, create tabs
along the upper edge with a snap lock punch. The tabs must
be raised on the outside face of the panel (shown on the
next page).
Fit the panel on the corner, making sure to overlap the
preceding panel.
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CertainTeed Vinyl Siding Installation Guide
undersill
trim
vinyl fascia
cap fascia
board
nail in slot
opening
1/8"
3/4"
1-1/2"
For installations that include soffit
Nail the undersill trim in place along the top of the fascia
board. Then nail F-channel along the bottom outside surface
of the fascia board (shown).
The fascia panel will have to be rip cut to fit over the fascia
board and F-channel. To determine the width of the panel,
measure from the slot in the undersill trim to the bottom of the
F-channel. Deduct 1/4" and cut (shown).
Use a snap lock punch to create tabs 1/8" below cut edge.
Punch tabs every 6", with the tabs raised on the outside face
of the panel.
Install the panel by hooking the bottom of the fascia panel
under the F-channel and pushing the top into the undersill trim
(shown).
Continue to install the fascia as described on page 82.
Aluminum fascia
The techniques used to install aluminum fascia panels are
similar to those used with vinyl– with three exceptions. There
is no special undersill trim to use with aluminum fascia.
Aluminum fascia is made without nail slots, so you have to
pay attention to proper nailing techniques. And corners are
handled differently.
Install drip edge, gutter, or all-purpose trim along the top of
the fascia board to receive the top edge of the fascia panel.
Slip the fascia panel in place. Then nail the underside of the
panel. Nail every 24", keeping the nails lined up with the soffit
V-grooves.
For best appearance, first drill a slightly oversized hole. Nail
the fascia with painted trim nails, using a light touch.
At the outside corners, bend a 1" flange at a 90° angle so
it turns the corner. Then cut the overlapping fascia at a 45°
angle. Position the panels and nail.

NOTE: If you need a piece of nonstandard size fascia,
use a portable brake to form it from aluminum trim sheet.
Install and nail using the same techniques you used with
standard fascia panels.

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