M-d Building Products 71506 Backer Rod 5/8 Inch X 20 Ft

Product Description

The M-D BUILDING PRODUCTS 71506 is a closed-cell polyethylene backer rod used as a pre-caulking filler for gaps and joints. It compresses into openings before sealant is applied, giving the caulk a proper backing surface and controlling the depth of the sealant bead. At 5/8 inch in diameter and 20 feet in length, this gray rod handles gaps and openings larger than 1/2 inch by 1/2 inch. Its nonabsorbent, closed-cell construction resists moisture absorption, keeping the joint assembly stable over time. Licensed contractors and skilled tradespeople working on window, door, or expansion joint sealing installs this product as a standard pre-caulking step.

This backer rod is suited for residential and light commercial sealing applications where gaps exceed the recommended maximum span for sealant alone. Typical scenarios include window and door perimeter sealing, concrete expansion joints, masonry control joints, and penetration seals through walls or floors. It is especially useful when joints are deeper than they are wide, where applying sealant without backing would result in excessive material use or poor adhesion geometry. The 20-foot length covers most single-opening or short-run joint applications without splicing.

Key Features

• Closed-cell polyethylene construction prevents moisture absorption into the backer material
• Nonabsorbent design prevents 3-point bonding, allowing the sealant to flex correctly at two surfaces
• 5/8 inch diameter fits gaps and openings larger than 1/2 inch by 1/2 inch
• 20-foot continuous length reduces splicing in longer joint runs
• Gray color blends with common joint substrates during installation

Compatibility

Designed as a standard pre-caulking backer rod for use with most elastomeric and polyurethane sealants in residential and light commercial gap-filling applications where joint openings exceed 1/2 inch by 1/2 inch.

Installation Notes

Backer rod is typically installed by caulking and weatherproofing trades prior to sealant application. Press the rod into the joint to the correct depth so the sealant bead achieves the proper width-to-depth ratio — consult the sealant manufacturer's instructions for the recommended depth. Do not stretch the rod during installation, as stretching can reduce its cross-sectional diameter and compromise the backing. Verify joint surfaces are clean and dry before placing the rod and applying sealant.

Technical Specifications

• Material: Closed-cell polyethylene
• Diameter: 5/8 inch
• Length: 20 feet
• Color: Gray
• Weight: 0.163 pounds
• Cell Type: Closed-cell, nonabsorbent

Standard Information

• Brand: M-D BUILDING PRODUCTS
• Manufacturer Part Number: 71506