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What are Backer Rods and How are they Used?

September 13, 2016

When there are joints between tiles or other components/units of construction material, backer rods are used to fill up the vacant space. Similar to cylinder shaped foam rods, they are also available as flexible cords, sheets and planks. The builders first place these rods in grooves or cracks that cause the empty space and then firm them up with mortar, adhesive sealants or chinking.

Backer rods
provide many useful features:

1.     Firmness

2.     Resistance to wear and tear

3.     Sturdiness

4.     Decoration

5.     Insulation from air, water, heat, dust and chemicals

6.     Save time and money


Backer rods come in two types – open-cell and closed-cell. These two varieties can be used either separately or together depending on the need. Open-cell rods are relatively less thick allowing more air circulation while the closed-cell variety pack more density. Being more pliant due to their softness, open-cell rods are easy to install than closed-cell ones. Open-cell rods are preferred for indoor purposes with lesser dampness while the closed-cell type is favored for outdoor purposes like platforms, courtyards and passageways.

Here are the common uses of backer rods:

1.     Laying floors/tiles

2.     Ornamental wall paneling

3.     Sealing  and glazing doors/windows

4.     Stoneware

Backer rods vary from a quarter inch to four inches or more in diameter. They are either made to order or sold in pre-determined sizes. Different construction requirements warrant different types and dimensions of these rods. They come in polyethylene and polyurethane forms.

Advantages of using backer rods:

1.     Cheaper and time-saving replacement for costlier caulking compounds

2.     Enable hour-glass shaped filling enabling sealants to manage unavoidable joint movements better

3.     Being a bond-breaker, backer rods are non-adhesive to cold-applied sealants thereby preventing three-sided adhesion of joints

4.     Control and enhances sealant usage

5.     Repels moisture and reduces air leakage


It may appear that the role backer rods play is trivial or insignificant, but they are indispensable to builders in ensuring that the seals in joints perform well.