PEF Rod

PEF rod is a flexible, closed-cell polyethylene backing rod used behind sealant in expansion and control joints, controlling sealant depth and stopping the sealant from bonding to the base of the joint. The range covers PEF rod in multiple diameters supplied in reels and boxes, alongside a closed-cell pipe insulation product built from the same polyethylene foam family.

Get the joint depth right before the sealant ever goes in.

PEF rod is lightweight, waterproof, and non-absorbent, so it holds its shape and position inside a joint without absorbing moisture or adding weight to the finished seal. Correct backing rod diameter reduces sealant consumption and gives a consistent, professional bead profile along the full length of a joint. The pipe insulation product is fire resistant and pre-split for easy fitting around existing pipework.

How to choose the right PEF rod

Selection depends on the joint width and depth, and whether the job needs backing rod or pipe insulation.

Standard expansion and control joints. PEF rod sized around 25-30% wider than the joint opening compresses slightly into place, holding position without adhesive while controlling the depth of sealant applied above it.

Long runs of joint. Reel format suits longer, continuous joints such as facade or control joints, reducing the number of joins compared with shorter lengths.

Shorter or smaller jobs. Boxed lengths suit smaller quantities or jobs with multiple shorter joints, without the handling bulk of a full reel.

Pipe protection and insulation. A pre-split, fire-resistant pipe insulation product is used to insulate and protect pipework, rather than controlling sealant depth in a joint.

Technical differentiators

• Structure: Closed-cell polyethylene foam doesn’t absorb water or add moisture into the joint
• Sizing: Diameter should generally be around 25-30% larger than the joint width to compress into place without adhesive
• Format: Reels for long continuous runs, boxed lengths for smaller or multiple shorter joints
• Water resistance: Rod itself is waterproof, helping protect the joint from moisture ingress from behind the sealant
• Pipe insulation variant: Fire resistant and pre-split, distinct from backing rod and used for pipework rather than joint sealing

Not sure which PEF rod diameter or pipe insulation size suits the job? Use our product selector tool, contact us directly, or find your nearest stockist. See the full Sealants range for compatible sealants.