About this product
Closed-cell backer rod is a round, flexible foam cord that roofers, sheet metal mechanics and glaziers press into a joint before applying sealant. It controls how deep the sealant goes, gives the bead a curved back so it stretches evenly, and keeps the sealant from bonding to the bottom of the joint, which lets it move with the building instead of tearing.
Backer rod maker Nomaco advises sizing the rod 25 to 50 percent larger than the joint, so a 1/2″ joint takes about a 5/8″ rod and a 3/4″ joint about a 1″ rod. Press it in evenly with a blunt tool, and do not puncture or over-compress it. Closed-cell foam does not soak up water, which suits exterior metal work, and it is meant for cold-applied sealants, not hot-pour products.
On standing seam roofs, some installers also lay a 1/2″ backer rod under wide, flat panels to give the pan light support and cut down on visible oil canning, especially with aluminum. Ask us how that is usually done with the panel profile you are installing.
Backer rod is the first step of a good sealant joint, so it usually goes out with Adseal (304 ml tube or 600 ml sausage) or Geocell 2300 Combo or Geocell Phantom sealant, plus Butyl Tape for lap joints.
It is available from our New Brunswick, NJ warehouse; call (732) 561-4275 to check stock, or add it to your quote.
Specifications
| Type | Closed-cell foam backer rod |
|---|---|
| Use | Sealant joint backing; panel support under flat pans |
Goes with it
Questions
What size backer rod do I need?
Go slightly larger than the joint width so the rod stays compressed in the gap. Measure the joint and we will match a diameter.
Which sealant goes over it?
Adseal and Geocell sealants are both in the catalog; choose based on the substrate and joint movement.