Mastic J-Block with Electrical Box, 8-3/8 in. x 12-1/2 in., Multiple Colors

This Mastic J-Block with electrical box is a siding mounting block, 8-3/8 in. x 12-1/2 in., that houses an outdoor electrical box behind siding. It comes in color 144 Misty Shadow, 498 and 803, sold per carton or each depending on color. It pairs with Mastic vinyl siding installations for mounting exterior lighting and outlets.

Key Features:

• Integrated box: Combines a J-block mounting block with an electrical box for exterior fixtures and receptacles.
• Siding ready: Designed to mount on Mastic vinyl siding installations.
• Generous size: 8-3/8 in. x 12-1/2 in. face covers siding cuts and provides a solid mounting surface.
• Color choices: Offered in Misty Shadow (144) and two additional Mastic color codes, 498 and 803.
• Clean finish: Gives exterior lighting, outlets and fixtures a finished, weather-tight appearance.

Specifications Table:

Coverage & How Much You Need:

Not applicable; each unit covers one mounting location for a fixture or outlet.

Fit and Compatibility:

Designed for use with Mastic vinyl siding. Electrical box, fixture and wiring supplies are field-provided; other Mastic J-channels and trim accessories are sold separately.

Frequently Asked Questions (FAQ):

Q: What is included?
A: One J-block mounting block with an integrated electrical box in the selected color.

Q: What size is it?
A: 8-3/8 in. x 12-1/2 in. in every color on this line.

Q: Which colors are available?
A: 144 Misty Shadow, 498 and 803.

Q: How is it installed?
A: It is trimmed into the siding course at the fixture location, providing a finished opening and a mounting point for the electrical box.

Q: Is the electrical box included?
A: Yes, the J-block comes with an electrical box as part of the assembly.

Expert Verdict Reviewed by the SuperArbor Pro Desk

Order the color code that matches your siding, and install the block in the same course layout so the trim reads as part of the wall. Provide an appropriately rated exterior-rated electrical box and seal per the fixture manufacturer’s instructions. For heavier light fixtures, verify the backing behind the block can carry the load.

Electrical work should follow local code; have a licensed electrician make wiring connections.

Get a Mastic J-Block with electrical box color-matched to your siding for a clean exterior fixture install.