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Installing Vertical Siding


Preparing Wall Surfaces

For the most part, the wall preparation instructions given for horizontal siding also apply to vertical applications. The key requirement, of course, is that you start with a smooth, level and rigid substrate (plywood, wood composite, rigid foam or fiber sheathing).

NOTE: Never install vinyl siding over open furring strips or studs. Always check with your local building code official.

With vertical siding, however, you may have to complete an extra step to provide solid nailing points along the vertical edge of the siding panel. The need for this added step depends on the type of substrate used and the nature of the construction project.

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The procedure is virtually the same as that described earlier. However, instead of snapping a chalk line 2-1/4" above the low point, snap it 1" above the low point.

NOTE: When installing vertical siding in high wind areas, position the fasteners at the top two nail slots of the panel


Install outside and inside cornerposts using dimensions and procedures

NOTE: Unlike the preparation for horizontal siding, do not install a starter strip for vertical siding.


Snap a base line 1" above the low part of the house. Apply J-Channel along the top and bottom of the walls to receive the siding panels. Drill drainage holes every 2 feet along the face of the bottom J-Channel prior to installation. Install the bottom J-Channel (illustration 1A). Overlap J-Channels 3/4". To do this, cut out a 1" section of the nailing flange and face return   
If you prefer to use drip flashing with the J-Channel along the bottom of the wall, fabricate the lengths you’ll need from aluminum coil stock of a color to match the siding.   
Install inverted J-Channel along the top of the wall, under the eave. Here again, leave a 1/4" gap between J-Channel and cornerposts. Overlap J-Channels 3/4" to allow for expansion. When positioning the upper J-Channel, be sure to allow for expansion of the siding panel. In most cases, position the J-Channel at a point equal to the length of the panel plus 5/8" (1/4" for upper expansion and 3/8" for lower expansion).


If you’re going to install soffit, you may want to install the receiving channels for the soffit at this point.   
If a wall requires more than one course of siding, you can proceed in one of three ways:

  • Use two lengths of J-Channel, back-to-back, at the joint between the two courses.
  • Use a combination of one length of J-Channel and one length of drip cap.
  • Use a double channel lineal and flashing where required.

Snap a chalk line parallel to the bottom J-Channel, at a height equal to the length of the lower panel plus an allowance for expansion. For example, if the lower panel is 144" long and you’re adding 1/2" for expansion (because the temperature is above 40°F), you strike a line 144-1/2" from the bottom J-Channel. Nail inverted J-Channel along this line to receive panels from below. Leave a 1/4" gap between J-Channel and cornerposts. Overlap the J-Channels 3/4". Prepare for the second course by applying head flashing above the just-installed J-Channel. Then nail J-Channel over the flashing to receive the upper panel.

NOTE: Some installers prefer to use formed aluminum flashing in place of vinyl drip cap as the receiving channel for the lower panel. This is also an acceptable approach.


Follow the procedure here

If using double channel lineal: Measure the length of the lower panel, then subtract an allowance for expansion. Snap a chalk line parallel to the bottom J-Channel, at a height equal to your measurement. Position the lineal so the interior peak of the lower channel runs along the chalk line. Leave a minimum 3/8" gap between lineal and cornerposts when the ambient temperature is higher than 40°F. When the ambient temperature is below 40°F, leave a 1/2" gap. If necessary, overlap lineals 1-1/4".


Follow the instructions described earlier under the section “Preparation for Horizontal Siding”.   
Plan the panel layout Correctly installed vertical siding should have a balanced appearance. This means that if you were to draw a vertical line down the center point of a wall, you’d have an equal number of panels to the right and left. If you had to trim panels to fit, the end-most panels would be of identical width.   
To create this pleasing appearance, divide the space to be covered by a partial panel over both ends of a wall. For example, if a wall required 25 full panels plus 10", you would rip cut two 5" lengths of panel to create the end pieces.


In a vertical siding installation, most of the expansion is downward. So instead of allowing equal space for expansion at both ends of a vertical panel, leave more space at the lower end: allow for 1/3 of the total expansion at the top of a panel and 2/3 of the total expansion at the bottom.   
For example, if the total expansion equals 3/4" (3/8" + 3/8"), allow 1/4" at the top and 1/2" at the bottom. If the total expansion equals 1/2" (1/4" + 1/4"), allow 3/16" at the top and 5/16" at the bottom.

NOTE: Always position top most nail at the top of the top most full nail slot. Center the remaining nails in the slots. When installing siding or accessories vertically, make sure the bottom of the panel can expand downward without interference.

Cut the first of the partial panels (if partial panels are necessary). Mark the cut line by measuring from the nail hem edge. Rip cut the panel. Do not cut off the nail hem. Use a snap lock punch to create locking tabs along the cut edge. Space the tabs 6" apart.   
Before installing this partial panel into the outside cornerpost, provide additional support at the cut edge to compensate for the locking channel that was trimmed off.   
To do this, insert furring into the channel of the outside cornerpost and nail it to the substrate. After furring, insert a length of undersill trim into the cornerpost and nail it to the furring. Finally, slide the cut edge of the panel into the undersill trim, making sure to engage the snap locks.

NOTE: When applying overlapping materials, you may have to make new slots to avoid pinning the underlying accessory.

Using a level, make certain this panel is plumb. Nail every 12". Follow the same nailing procedures described for horizontal siding.   
Install the next panel. Lock the panel into the preceding panel, then nail every 12". Continue with succeeding panels.   
When necessary, cut panels to fit around doors and windows. When marking the cut, remember to allow for expansion.   
The method used to install panels around doors and windows is determined by the need to cut a panel and the position of that cut. If a cut was made next to a remaining V-groove, insert the panel into the J-Channel. If a cut removes the support provided by a V-groove, use the procedure described above to provide support for the trimmed edge.   
To finish the first course of a wall, cut the final panel to size and install it in an outside cornerpost, using the method described above.

NOTE: The cutting and supporting procedure described above is also used when fitting panels into inside cornerposts.


When installing vertical or Board & Batten siding on a gable end wall, you should try to create a balanced appearance.

There are two ways to do this:   
You can start from the center of the wall and work toward the sides. Begin by finding the center point of the wall (beneath the peak) and draw a plumb line. Nail two lengths of J-Channel, back to back, along this line. Be sure to flash underneath the J-Channel to help prevent water damage due to water seepage between the J-Channels. Cut the upper end of the first panel to the proper height and slope. Remember to allow for expansion.

NOTE: To guide the cutting of the upper end of the panel, make a pattern duplicating the gable slope.

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Insert the panel into the J-Channel along the gable slope.   
Use a level to make certain the panel is plumb. Nail every 12". Continue cutting and installing panels. Then repeat the procedure on the remaining half of the gable end.   
If you want to work from one end of the wall to the other, begin by centering a panel under the center of the peak. Mark the position of the panel on the wall, then measure the distance from the left (or right) cornerpost to mark for the left (or right) edge of the center panel.   
If you need a partial panel, cut it and install it at the cornerpost, following the procedure described on pages 40-43. Cut the upper end of the panels to proper height and slope, following the procedure described above. Remember to allow for expansion.