Backer Rod
A closed-cell foam rod pressed into a joint before sealant, setting the correct sealant depth and preventing it bonding to the joint base.
On an actual building
Sealant must bond to two faces only. Bonded on three sides it cannot stretch and tears itself apart, usually within the first seasonal cycle.
What we most often have to correct
That it is a filler to save sealant. It controls both the depth-to-width ratio and the adhesion geometry.
Terms that come up alongside this one
- Three-Sided Adhesion
A sealant bonded to the base of a joint as well as both faces, so it cannot deform freely as the joint moves..
- Sealant Movement Capability
The percentage of a joint's width that a sealant can accommodate in extension and compression without failing, stated by the manufacturer..
- Expansion Joint
A deliberate gap through a structure that allows adjacent parts to move independently under thermal and structural movement..
Backer Rod — questions we get asked
What does backer rod mean in waterproofing?
A closed-cell foam rod pressed into a joint before sealant, setting the correct sealant depth and preventing it bonding to the joint base.
Why does backer rod matter on a real project?
Sealant must bond to two faces only. Bonded on three sides it cannot stretch and tears itself apart, usually within the first seasonal cycle.
What do people commonly get wrong about backer rod?
That it is a filler to save sealant. It controls both the depth-to-width ratio and the adhesion geometry.
Have a building showing this?
If a term on this page describes something you are looking at, a site inspection will tell you how far it has gone and what it needs. It costs nothing.
Mon–Fri 08:00–18:00 · Sat 09:00–16:00 · Jogeshwari West