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July 17, 2014


In most construction projects, gaps have to be filled in order to achiever airtight properties. Filling of gaps between building materials is done using backer rods and an appropriate sealant. The size of gaps to be filled does not matter since the rods come in a variety of diameters to suit different sizes of gaps. There are two main types of backer rod used for internal and external applications. When it comes to internal environments where moisture content is low, open cell rods are used. Contrary to this, closed cell rods are used to fill gaps in external environments where moisture content is high. A brief study of the two versions will help one understand their applications better.

Open cell backer rods are made of breathable airy foam. They are less dense than closed cell versions. The fact that they are breathable means that they are only appropriate for dry indoor environments. They are soft and flexible in nature hence very easy to install. Very thick pieces can be forced into small gaps easily. For this reason, they are used to fill irregular gaps with a varying width. They are known as the universal type because they can fit numerous applications. However, they are poor insulators hence cannot be used for external projects.

Closed cell backer rods are denser in nature and firmer as compared to the open cell rods. They are harder to bend and fit into gaps hence quite hard to install. Their microstructure consists of closed cells, which are responsible for waterproofing properties. Their nature enables them to stand vary harsh external environments. Most builders use them to fill small gaps to achieve an airtight properly insulated joint. From the discussion above, there is one major distinction that will help the builder to establish the best type of backer rod to use, that is, the environment.