How to Install Vinyl Siding Over Lap Siding

In recent years vinyl siding has become one of the most popular choices for homeowners and builders in the United States. Aside from being economical, vinyl siding has become increasingly attractive since it was first manufactured in the 1970's. A nice feature of vinyl siding is that it can be installed over traditional lap wood siding. The underlying lap siding must be in a condition that protects the house. Fastening rigid foam insulation over the lap siding provides a consistent surface over which the vinyl siding channels, and then the interlocking panels, can be affixed.

Vinyl siding can be installed over lap siding; but first rigid foam insulation must be fastened to the house.

Inspecting the Lap Siding and Installing Rigid Foam Insulation

Step 1

Inspect the existing wooden lap siding. Vinyl siding does not provide consistent water-resistance for your home, so it is essential that the underlying siding is intact and prevents water from seeping into the house's framework. In your inspection, look for signs of rot or water damage. Use a metal rod to prod at suspect areas and test for softness. Replace any damaged or rotten siding boards before you attach the foam insulation and the siding.

Step 2

Fasten 1/2-inch thick sheets of rigid foam insulation to the house. Hammer the sheets in place with galvanized roofing nails driven through the insulation and into the underlying lap siding. While the rigid foam insulation will provide some additional energy efficiency to your home, its main purpose is to create a level, even surface over which your vinyl siding will be affixed.

Step 3

Where necessary cut the rigid foam insulation by marking it; then slice it halfway through with a utility knife. Flip the piece over and snap it in half, then slice through the film holding the 2 pieces together.

Step 4

Cover all the surfaces to be sided with vinyl with the rigid foam insulation.

Installing Soffit Pieces and Fascia

Step 5

Install your soffit and fascia pieces first. The soffit panels fit on the underside of your roof's eaves between the wall and the outermost roofing rafter. Fasten polyvinyl chloride (PVC) J-channel along the edges of the panels where they meet the wall and the outermost rafter. Orient the channel so that the slot into which the soffit panel will fit is facing the slot on the J-channel on the opposite side of the soffit.

Step 6

Cut the J-channel to length with a pair of tin snips and fasten in place with galvanized roofing nails. Drive the nails through the nail slots in the J-channel. Whenever fastening vinyl pieces always leave about 1/16 to 1/32 inches of the nail shafts exposed to allow for expansion and contraction in varying weather.

Step 7

Intall "T" channel pieces where two soffits meet. T-channel is similar to J-channel, but instead of having only one slot into which the panel fits, the T-channel has 2 back to back slots. It works essentially like 2 pieces of J-channel laid back to back. The T-channel can be cut and fastened either at a 90 degree angle from the corner where the soffits intersect, or it can be run at a 45 degree angle. The choice is up to you.

Step 8

Cut the soffit panels to width and length with a utility knife. Insert one end of the soffit panel into the J-channel, then carefully bend the other side and work it into the opposing J-channel. When you reach the corner, bend and fit the soffit panels into the T-channel.

Step 9

Fit the fascia pieces over the outermost roofing rafter. The fascia is primarily decorative and serves to cover the rafter so it matches with the rest of the siding. If necessary, cut the fascia pieces to height with a utility knife or a circular saw with the blade installed in the reverse direction from how it would normally be oriented. Nail the fascia panel every 24 to 36 inches with galvanized nails.

Installing Your Inside and Outside Corner Pieces, Starter Strip and Utility Trim

Step 10

Use a chalk line to run plumb guidelines along the inside and outside corners of the house. Refer to these lines as you fasten your inside and outside PVC corner pieces.

Step 11

Cut your inside and outside corner pieces to length with a pair of tin snips or your circular saw with the blade on in reverse. Then fasten them in place with galvanized nails run through the center of the existing nail slots. Maintain the 1/16 to 1/32 inch wiggle room when you drive your nails. If you end up needing to run more than 1 corner piece to cover a span, overlap the pieces by first cutting away 1 inch of the nailing flange on the upper piece. Then overlap the pieces by 3/4 inch. The extra 1/4 inch allows for the natural expansion of vinyl in high heat and prevents buckling.

Step 12

Use a level and a chalk line to mark your baseline around the entire perimeter of the house. Refer to the manufacturer's instructions regarding how high from the ground the siding should start. Use this guideline to align your starter strip.

Step 13

Fasten the aluminum starter strip between the corner pieces along the base of the house. The starter strip is a folded aluminum bracket into which the base of your first course of siding panels will fit. Wherever it is necessary use tin snips to cut the starter strip. Leave 1/4 inch of space between adjacent runs of starter strip. Hammer the starter strip in place with galvanized nails driven through the nail slots. Be careful not to overdrive the nails when fastening starter strip.

Step 14

Fasten J-channel around your doors and window frames. Use a miter saw with the blade installed the reverse to make 45 degree cuts where 2 perpendicular pieces of J-channel meet. Where a piece of J-channel along the top of a window or door meets a piece along the side, extend the top piece about an inch beyond the side piece. Notch the lower edge of the top piece and bend the notch down so it lies inside the channel of the side piece. This will help to direct water down the J-channel and will prevent water from seeping into the window sill or door jamb.

Step 15

Run J-channel along the underside of your sloped roof eaves. Cut the channel to fit with your tin snips and hammer it in place in the same manner as with the other channel pieces.

Step 16

Install utility trim along the underside of windows, and along your horizontal roofing eaves. Utility trim serves to lock the cut top edge of the panel into place. Similar to J-channel, cut utility trim with your tin snips and fasten it by driving galvanized nails through the nail slots.

Installing Your Siding Panels

Step 17

Start with the lowest course of siding panels and lock the bottom edge into the starter strip. Position the panel so that it starts 1/4 inch beyond the back edge of the J-channel. Nail each panel with galvanized nails driven directly through the center of the nail slots. Leave 1/16 to 1/32 inches of the nail's shaft exposed to allow for expansion.

Step 18

Where 2 panels overlap, make the overlap about 4 inches. Stagger your overlaps from one course of siding panels to the above course.

Step 19

As you work your way up lock the lower edge of one panel into the channel on the upper edge of the panel beneath. Check your level as you go; about every 3rd or 4th siding course. If you lose your level, make a series of small adjustments over the next several courses; as opposed to making a single, glaring repair.

Step 20

Trim your panels to length with your tin snips. Where the panels need to be cut to fit around windows and doors, use a utility knife. Likewise, where you need to cut the panels at an angle to fit into the J-channel along sloped roofing eaves, mark the panels with a grease pencil and cut them with a sharp utility knife.

Step 21

Where the cut top edge of a panel intersects utility trim, for example under windows and along horizontal eaves, use a snap lock tool to punch lugs into the top cut edge. Position these lugs 6 inches apart and make sure when you punch them that the lugs end up on the face of the panel. Push the cut edge of the siding panel up until it locks into the utility trim.