Mounting blocks provide a flat surface for installing outdoor light fixtures, electrical boxes, or other mountable units on vinyl siding. They also come in several different styles that provide a neat trim around a vent or hose bib. The steps to learn how to install a vinyl siding mounting block may be done on existing siding or prior to new siding installation.

How to Install a Vinyl Siding Mounting Block Step by Step

1. Turn electricity supply off if you’re working on a block over electrical wires.
2. Take the trim ring off of the mounting block and set it aside. You will put it back on later.
3. Position the block against the vinyl siding in the desired location.
4. Trace around the block (NOT the flange) with a pencil on the siding.
5. Cut through the markings with a utility knife or oscillating tool.
6. Opening should be 1/8 to 1/4 inch larger than block around all sides. You want a loose fit when completing the steps to learn how to install a vinyl siding mounting block.
7. Find the edges of the siding section over the work area.
8. With your hand or a siding removal tool, pop the siding section loose. (Siding section will remain nailed in place along its top.)
9. Gently lift the loose vinyl siding section and slide the mounting block underneath it.
10. Fit the hole that you cut over the block.
11. If block is too small or too tight, cut the siding a little more.
12. Once the siding fits loosely over the block, check the position of the block with a level.
13. Fit a galvanized screw on your power drill’s screwdriver bit.
14. Position a screw in the small gap between the block and the siding on one side.
15. Drive the screw through the block’s flange into the wall.
16. Confirm that the block is still level before driving a screw through the flange on the other side.
17. Finish adding screws around all sides of the flange.
18. Caulk around gaps in mounting block to waterproof the installation. This is especially important when mounting electrical components.
19. Attach the trim ring to cover the seam where the mounting block and vinyl siding meet.
20. Pop the loosened siding section back into place along the bottom.
21. If you could not find a mounting block that matched your vinyl siding color, take a scrap of siding that you cut away to the paint store.
22. Have the paint store mix a matching color.
23. Paint the mounting block.

When installing a mounting block before siding installation:

1. Put the mounting block into position against the exterior wall sheathing.
2. Confirm that the block is level.
3. Drive screws around the flange.
4. Waterproof the edges of the mounting block with sealant.
5. When installing vinyl siding, cut the siding to fit around the block.
6. Attach the trim ring.