I have several expansion joints in my home’s concrete sidewalks that need to be repaired/refilled. There is a lot of info regarding this out on Internet…too much in fact. I can’t determine from online research if it is most appropriate to use asphalt impregnated felt/fiber board for this, or if foam backer rod and Sika-flex is what is required (or best solution). Areas to be repaired are about 1/2-3/4 inches wide, ~4 feet long, and ~4 inches deep (i.e. fairly typical).

I prefer the look of the fiber board; if I decide to go with it, I am not sure how best to fix or “glue” it in place?


It doesn't really matter what the material is as long as it prevents rigid materials, such as sand and ice, from occupying the space. Don't overthink it.

If you go with fiberboard, I wouldn't worry about bonding it in place. The asphalt will do that to some extent, but friction will do most of the work. The drawback to fiberboard is in sizing--it may not fit exactly as it did when the concrete was poured.

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