Field & trade terms
Backer rod
Backer rod is a compressible foam cord stuffed into the back of a joint before it's caulked. It does two jobs at once: it controls how deep the sealant goes so the bead has the right shape, and it prevents the sealant from grabbing the back of the joint, because a proper sealant joint bonds to only two faces so it can stretch as the joint moves. Skip the rod, or use the wrong type, and the sealant ends up too thick, three-sided and prone to tearing.
Run it with the Photo Gate
Waterproofing inspection checklist
12 items · 26 photos required
Why it matters
A sealant joint only performs if it can flex with the movement it was designed for, and three-sided adhesion locks the bead so it splits instead of stretching. Backer rod is the small, unseen piece that makes an expensive sealant work or, done wrong, wastes it. Closed-cell rod in a wet joint or a rod that outgasses can also make the sealant bubble.
What an inspector looks at
The check is that backer rod of the correct type and diameter is set to the right depth for the joint width, giving the proper sealant profile and two-sided bond, with no rod left proud or pierced. It's really verified together with the sealant joint it backs.
Because RTI closes items on a photo, the prepped joint is documented before the sealant covers it, with rod set to depth in a clean joint shown in frame as proof the bead had the backing it needs to last.
Checklists that put backer rod to work
Free, field-ready checklists, each with the photo every item needs before it can be submitted.
Related terms
- Sealant jointA joint filled with elastic sealant to keep water and air out while still flexing as the two sides move apart and together.
- Control jointA planned weak line cut or tooled into concrete or masonry so shrinkage cracks form where you want them instead of at random.
- Weep holeA small opening left at the base of a cavity wall or window so water that gets behind the face has a path back out.
- GroutA flowable cementitious or resin mix used to fill voids, bed plates and cells, or pack the joints between tile or masonry units.
- Anchor boltA bolt cast into or drilled into concrete that ties structure (sill plates, columns, equipment) down to the foundation.
- Embed plateA steel plate with anchors cast flush into concrete so later steel, connections or supports have something to weld or bolt to.
Knowing the term is step one. Proving it is the job.
RTI holds the submit button until every mandatory item is answered and the photos are attached, then chains the record so it can be proven untouched later.
30-day trial · No card required