The following FAQ's relate to Backer Rod

Can I use anything other than backer rod as a bond breaker?

Yes! Mylar tape (which is clear packing tape) is also a common form of a bond breaker. If you are already at the desired depth, just place a piece of mylar tape over the back of the joint and apply your caulking or chinking.

Do I have to fill all the tiny cracks?

We have to define what is meant by “tiny”. Generally, it is good practice to seal with caulking or chinking (and backer rod) checks of ¼“ width or wider that exist in the upper curvature of logs, which otherwise would be left open to fill up with moisture and decay fungi spores. Prior to sealing them, however, it is good practice to also direct a good wood preservative into them to retard any decay processes that may have already begun. The very small micro-checks that are barely visible can usually be sealed adequately with whatever stain is applied to the surface of the logs. The most problematic checks are the “in-betweeners” – smaller than ¼” and larger than the micro-checks. Other than applying some wood preservatives to these types of checks, there is no really good way to treat these types of checks yet.

Do I have to use backer rod when chinking?

Yes. In order for the chinking to expand correctly, it is necessary to have some sort of bond breaker applied. If the joint is not very deep (less than 1/2”), clear mylar tape will do the trick. In addition, one needs bond breaker behind their chinking to maintain the warranty on the product.

Do I need to chink or caulk my “chinkless” style log home?

The short answer is you probably will – if not now, then later.

Here’s why. Often log home manufacturer design their homes to fit tightly together – no chink line is required. This is a look that appeals to many customers. Generally, when the logs are stacked, an “internal” seal is installed (either a bead of caulking between the logs, a butyl tape, or something similar to insure a water - and air - tight home.) to insure a water tight home.

Two things happen over the next few years. First, as the logs dry out to their final moisture level, they move. This movement sometimes breaks the initial internal seals between the logs allowing cold air, bugs, and water to come into the home. It is difficult to tell exactly where the seal is broken, so spot repairs are sometimes not effective. At this point, some homeowners choose to caulk the home between log courses to fully seal it up. Conceal is an ideal product for caulking these joints because it is textured and matched to the popular stain colors out there. So the Conceal caulking is truly “concealed” to insure the desired “chinkless” look.

Second, as the logs dry out checks will appear and get bigger. These checks (on the home’s exterior) will need to be treated with Penetreat to prevent rot, stained to prime the inside surface, and then caulked with backer rod and either Log Builder or Conceal. Caulking these checks is essential to preventing rot, prolonging the life of the stain, and keeping water out of the home.

My chinking / caulking is torn. How do I fix it?

There are a number of reasons why chinking or caulking can tear:

a) The chinking / caulking line is too small for the log diameter. In general, the sealant line should be 20% of the diameter of the log. (i.e. a 10 inch diameter log should have a 2 inch sealant width.)
b) Improper application. Refer to the individual data tech brochures for each product for proper instructions.
c) There are generally a few “maverick” logs that have a higher moisture content than the majority of logs used on your home. Typically, once the mavericks have dried and caused their damage they don’t move much after that and the repairs are quite durable.

Repairing torn chinking is really rather easy. Start with a clean surface, gun chinking over the torn area, tool the chinking feathering it out onto the sound chinking in the joint. If no backer rod was applied, you may need to cut out the torn area, install backer rod, and then follow the remaining steps as noted above.

What is the difference between chinking and caulking?

“Chinking” in the log home industry has come to mean an elastic sealing material that looks like the old-fashioned Portland cement-based mortar in color and/or texture, used to seal the joints between logs. Chink lines can be fairly narrow or pretty wide. Backer rod or bond-breaking tape should always be used in back of the chink line in order to provide 2-point adhesion and allow the chinking to expand and contract to the maximum possible degree. Log Jam and Chinker’s Edge are both excellent chinking products.

“Caulking” is a similar material to “chinking”, but usually has no texture or a very light texture. Caulking also generally has more elasticity than chinking products. Because of this, caulking works better in smaller joints (i.e. ¼” to 2” wide). Caulking can be used to fill the horizontal cracks (called checks), create a continuous caulking line between the log rows, or as a stacker during construction.

What is the difference between open cell and closed cell backer rods?

Closed cell backer rod is probably the most common form of backer rod. It does not hold moisture and actually repels water. Closed cell backer rod comes in a variety of sizes ranging from 1/4” to 5” wide and can be used on both the exterior and interior of the home.

Open cell backer rod is a little easier to install because it is soft and pliable. It absorbs moisture so it causes the caulking and chinking to cure faster. Open cell backer rod is generally used only on the interior of the home. When open cell backer rod is used on the exterior of the home, if the caulking tears in any spot then the backer rod may absorb moisture, creating an ideal environment for rot.

What is the insulation R-value of the Chinking and Backer Rod?

Sashco’s thermodynamic analysis of this question has revealed the following:
a) A 9” pine log has an overall R-value of about 11.2.
b) The overall R-value of Log Jam + Backer Rod + the dead air space between the lengths of Backer Rod is about 10.6.
c) The overall R-value of a log wall combining chinked joints and the logs themselves is about 11.1. So, when Log Jam is properly installed with backer rod it has virtually no detrimental effect on the overall R-value of the wall.

What should I use to fill checks / cracks?

First, it is important to realize that the most worrisome checks are those on the upper curvature of the logs – making them the most prone to collecting moisture, fungi spores, dirt and other contamination. Larger checks on the lower curvature – while not prone to collecting moisture – can still lead to air infiltration into the house and provide entry access to flies and other insects. It is also important to realize that for approximately the first 1-2 years – especially if the logs are relatively green to begin with – that the initial checks will continue to open up as the logs dry out. If this continual “opening up” is likely to be severe – which could cause any caulk or chinking to fail – then it should be understood that some sealant repair may be needed after the logs have come into moisture equilibrium with the climate of the building site. For checks that are about 1/4” and larger in width (which are large enough to accept round backer rod), they can be effectively sealed with such products as Log Builder caulking, or, for a more textured appearance, Log Jam Chinking. It is always best to perform the following steps when sealing checks with caulking or chinking (starting, of course, with appropriate weather!):

1) Make sure there is no standing water in the checks to begin with (otherwise, there is a great risk of rot and premature sealant failure. Either remove the standing water or let it evapoprice, best price away.

2) As part of the overall application of a wood preservative, like PeneTreat, to the surface of the logs, extra wood preservative should be applied into the checks that are to be sealed with caulk or chinking – then allowed to dry.

3) It is usually best to apply the stain that will be used over the general surface of the house to the inner lips of the checks to be caulked or chinked – if the stain is compatible with the caulk and chinking to be used. Such a stain can act as a primer for the caulk or chinking and can greatly improve adhesion, especially when the walls are subjected to very wet weather. [Note: If the inner “lips” of the checks are dirty or significantly weathered, then these “lips” (i.e., the surfaces of the check which will be in contact with the caulk or chinking) need to be cleaned, down to bare, “sound” wood – in order to insure good adhesion of the stain and/or the caulk or chinking. Such cleaning can be accomplished several ways (including power washing and hand-sanding), but cob-blasting is the fastest, easiest and surest way to do the cleaning.]

4) Install the appropriate round backer rod, to the proper depth. [Note: The depth of the sealant bead should be approximately 1/2 of the joint width. This guideline will dictate how deep to press the backer rod into the check.]

5) Apply the caulk or chinking into the check with good pressure, forcing the sealant into intimate contact with the inner lips of the check. Do not just passively lay the sealant into the check recesses, which will have a tendency to not let the caulk or chinking properly “wet out” the surface – leading to poor adhesion.

6) Then, using a putty knife, shaped piece of wood, or a finger, “tool” the bead to further force the sealant into intimate log contact. While tooling, scrape the excess sealant from the sharp edges of the check and remove any material that may have smeared over the surfaces of the adjoining logs with a wet rag or sponge.


What’s the difference between closed and open cell backer rod?

The difference is partially explained in their respective names. Open cell backer rod is the type where each discrete cell – or bubble – within the foamed structure is not isolated from its neighboring cells; but rather has open channels connecting them all together. This type of structure is very much like that of a common sponge, with each cell in fluid communication with most, or all, adjoining cells. Most open cell backer rod products are made of foamed polyurethane elastomeric plastic.


Why do I have to fill the cracks? Why can’t I leave it natural?

Checks that develop in logs should be caulked if they are on the upper curvature of the logs and are wide enough to accept backer rod. These type of checks can be reservoirs for water. Also, spiral checks that lead into the home should be caulked. These spiral checks can collect water and direct it right into your home. Refer to our Log Builder Data Tec sheet for excellent instructions on how to caulk checks.

Why do I have to use backer rod?

Backer rod is a bond breaker, which means caulk and chink does not stick to it. When put behind caulking, it allows the caulking to only stick at the top and bottom of the joint where it touches the log (2 point adhesion). This allows the material to be pulled only in two directions (up and down) and react to movement like a rubber band.

If no bond breaker is in place, the caulking will stick to the back wall, top and bottom of the joint (3 point adhesion). This holds the caulking in place and does not allow it to move, causing failure.

Backer rod also greatly helps control the depth of the sealant as it is being installed to insure that the optimum amount of material is put into place. If too little material is installed, premature “cohesive failure” can occur. If too much is installed, the sealant is wasted and your costs are greatly increased.

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