Common types of Chinking, Caulking and Air Sealing for new and old log homes explained
What are the common types of Chinking, Caulking and Air Sealing for Log Homes? What works best and what should be avoided? What conditions cause failures? These are some of the common questions that customers customers ask me so lets explain.
Common types of Chinking, Caulking and Air Sealing
Historically log homes were
- Chinked with a mortar based product. Mortar was used alone or mixed with sawdust. Sometimes large voids were filled with strips of wood, metal lath or insulation then mortar was tooled into the voids and set in place.
- Oakum was a common sealant used in smaller voids. Oakum is fibrous rope that was placed between the voids using a hammer and caulking Iron
- Firring strips. On some log homes the craftsmen took the time to scribe saplings that fit between main logs.
- Moss was packed into the voids and between logs
- Mud
- Asbestos based caulk
- Or Nothing at all
Modern Log Homes most commonly are
- Chinked with Caulk that has sand and colored added to appear like traditional mortar.
- Caulked with Acrylic latex, polyurethane or silcone caulk
- Foam tapes can be applied during the construction process as the logs are layed
- Log Wool and fiberglass can be placed in Saddles and flyways as the before the logs are set during construction.
- Expanding polyurethane foam.
What works best and what should be avoided.
Historical log home air sealing is not the best at sealing air, water and vermin infiltration. Unless we are making repairs to old structures or historical structure where the owner or property manager want to maintain the historical significance, then we avoid using these methods.
Many caulking products manufactured before the 1970’s contained asbestos. If you have a old log home with old caulk a test should be sent to a lab to check for asbestos. If there is asbestos present then special procedures must be followed.
Modern sealing options do a much better job than the outdated methods. Many are flexible, elastomeric and do a wonderful job filling voids. As the logs and wood settle, expand and contract and moisture levels fluctuate modern sealing tends to move with the wood and maintain adhesion. They all have limitations and need to be applied according to the manufacturers specifications and in proper weather conditions.
Modern Chinking is basically acrylic latex caulk with sand and color added to give it a mortar look. When installed correctly it does a wonderful job at sealing water, air and small vermin. Log home chinking is most commonly used for larger voids up to 5 inches and not generally on Swedish Cope, Tongue and groove, splined or flat on flat constructed log buildings, although it can be. The two most popular products on the market are PERMA-CHINK and LOG JAM.
Log home caulking and chinking are very similar. The main difference is that caulking is generally used on smaller voids. Caulking specific for log homes works great around windows, doors, floors, HVAC penetrations and areas you would use caulk on a conventional home. Log home caulking products are different than other commonly used products. Caulking logs is different than caulking a toilet, caulking a shower or caulking a tub. I am unaware of any silicone caulk that works well on logs. In fact silicone caulk found at the big box stores can do more harm than good. If you have silicone caulk on your logs and it is more than a year old you can test what I am saying. Take a close look at it and find a area that has failed. Grab the caulk and give it a pull at a 90 degree angle. What happens? The caulk probably has little adhesion and as we call it in the log home industry “zipper” chances are, you are now standing with a long strand of caulk that probably took great time and effort to install. And if have ever tried to repair silicone caulk you probably know that nothing sticks to cured silicone caulk not even silicone caulk. You will have to remove the caulk and residue to put fix the failure. I am not trying to bash silicone there are some great products out there for seating glass during construction and replacement. If you are going to caulk or have a contractor caulk your log home then the product should be log specific. Depending on what has been applied to the logs there are times when Acrylic Latex will not adhere and then polyurethane caulk must be used. For example a deep penetrating oil based stain may cause adhesion failures with Latex based caulk. We can make recommendations for products based on compatibility with products you have already applied to you structure.
Some log home manufacturers recommend foam tapes for sealing between the logs. Foam tapes can be used on flat on flat, tongue and groove, spline and even swedish cope. Log seal works well while the drying and settling process takes place during the first few years of a new home. Unfortunately foam over time will retain memory, as logs move during seasonal changes you may begin to notice that the performance of foam gasket is not what it used to be. If you only have foam tape and your house is more than 5 years old I recommend that have an inspection to verify that your logs are air and water tight.
Log wool and fiberglass batts can be placed in saddles and flyways during construction. This will add R-Value to your walls but will do very little for air infiltration. As one colleague of mine puts it “without a vapor barrier, fiberglass is filterglass”. Therefor to achieve a good airseal you should caulk or chink log homes that only have Log Wool or fiberglass. If you plan on using this method in a construction project I recommend that you pay the extra money and purchase Log Wool Insulation. Log Wool is infused with borates and adds a protection against rot and insects.
Expanding Polyurethane foam or commonly referred to as Great Stuff is a underutilized product in the log home industry. I buy it buy the case and always have a supply of it in the tool trailer. One common source of air infiltration is outlets and junction boxes on exterior walls. Simply remove the junction box, apply the foam in the hole and replace the junction box. Take care, don’t add to much and verify that it didn’t enter into the box after the cure time is complete. If you have holes that squirrels or rodents have chewed entrances into a home. Kill or relocate the squirrel or squirrels. Shoot the with back of the hole with Great stuff. Put stainless steel wool in the hole and add more foam to the outside of the hole to hold the steel wool in place. Great Stuff pestblock works best for this application. This also works well for mice. One very common area that contractors overlook is sealing doors and windows. In the past there were not as many options as far as foam was concerned. Many door and window manufacturers would not warranty their product if expanding polyurethane was used to seal between the rough opening and window or door. Some of the older foams expanded with too much pressure and would cause problems. Fortunately the new foams are better and there is even door and window specific foam products. Very often we will remove casings or trim and seal the void with foam with great results. One important tip, keep Acetone around when using foams. Uncured polyurethane foams can be cleaned up with Acetone.
Each one of these options can fail for countless reasons. Common reasons for failures are:
- Incompatible product type such as stain and caulk combinations.
- Movement of logs during drying and settling.
- A low quality product was used. Improper application such as no backer or making the joint two thin or thick.
- Installing or applying the product in the wrong weather condition.
- Installing or applying products before the logs settle.
Or as with a majority of building failures the presence of water. The presence of H2O in general is bad. If your logs have high moisture content then there is a very good chance that you can grab a end of your caulk or chinking, if you pull on it and it zippers out then you know you have a problem or had a problem. I have seen this where the logs are dry but, the caulking or chinking was applied to green or high moisture logs shortly after construction and the adhesion failed. Some moisture problems can be fixed by cutting back vegetation, moving sprinklers, installing flashing, having properly installed and maintained gutters and downspouts. Some are much hard to fix especially if it is a architectural design flaw. Dormers, decks, log hand railings, smaller eaves and overhang may look cool but they are a headache when it comes to longevity of log structures.