An Inside Look: A perspective on varnishing your log home interiors

by Michael McArthur

Coating interior log walls with a transparent varnish has numerous merits worth considering. The psychological difference between non-coated and varnished logs is dramatic. Varnishing the log surface will enhance the depth of the wood grain and enliven your living space.

Leaving aside the positive aesthetic benefits, there is also a health benefit to sealing your log walls. Wood is a porous material and as a result, it has a tendency not to clean or dust well if left uncoated. If you are an allergy sufferer, dust mites and other airborne particles will cause allergic reactions. Log walls are an ideal location to accumulate and hold these various irritants. Because of its porous nature, cleaning a bare wood surface with a detergent solution will raise the wood grain and further aggravate its magnetic attraction to airborne particles. By filling the wood pores with a varnish type coating, a slicker, easier to “dust and clean” surface is created thus making the control of microscopic allergens on your log walls more effective.

There are primarily two types of varnishes that can be used on log walls: solvent-based or water-based. The major advantage of a water-based varnish over the traditional solvent-based type is its lower fumes. When working indoors, the harsh fumes and odor of a solvent-based varnish can be quite unpleasant, especially when good ventilation is not possible. Also, new environmental regulations are slowly phasing most of these solvent-based varnishes off the market. It should be noted that even water-based varnishes do have differing degree of fumes, some having more than others. (PolySeal™ water-based wood varnishes are some of the lowest in the industry).

A minimum of two and usually three coats of a water-based varnish is required to insure an adequate seal of the wood pores. Additionally, by applying multiple layers of finish, a thicker film is created thus magnifying and increasing the depth and clarity of the wood grain. At the same time, it provides a smoother surface that is easier and more durable to clean. Water-based varnishes also dry faster so a project can be completed in much less time. The hardness of the coating will depend on the resins used. For maximum durability, a polyurethane resin used alone or in combination with hard acrylic resins is your best buy. On log walls, a flatter satin or matte finish is usually preferred in order to minimize the glare of indoor lighting, whereas a gloss finish tends to be too reflective.

A WORD OF CAUTION... Never varnish interior log walls that still contain excessive moisture in them, generally above 18%. The reason is that a varnish is a clear or transparent enamel type coating that is not very breathable, especially when two to three coats are applied. When the heat is turned on during cold weather, the warm interior log walls draw the moisture to their surface. If enough moisture is present in the logs, peeling of the coating may occur and/or molds will grow BENEATH the coating causing ugly discoloration. This can only be remedied by removal of the coating. A rule of thumb is to wait one year and through a heating season BEFORE applying a varnish to the interior log walls. Also, consult with the log manufacturer for feedback on this log moisture issue.
In conclusion, varnishing your interior log walls provides great advantages to the home dweller for reasons of appearance and cleanliness. It is an investment well worth the cost that will be recouped many times over in the years of comfortable living it will provide.

*Reprinted from Winter 1999 issue of Log Core Newsletter.




*Michael McArthur was manager of the Log Home Products Division of the Continental Products Co. Continental manufactures wood coatings for the log home industry including PolySeal™, a waterbased polyurethane/acrylic interior varnish.

Camo Your Cracks

By Robert G. Kenel, Sashco, Inc

Checking is a natural occurrence that occurs in wood as it dries and acclimates to the surrounding atmospheric conditions. There are some things that can help reduce the effect of checking. Radial checking is the most common. That’s when the log shrinks as moisture is removed. To give you a better idea of how that looks. Picture the growth rings of the tree as a length of rope. It breaks as the wood dries. Know think the length of rope, it will shrink in length and get shorter. The longer the rope the more it more it will shrink. As these checks occur some will be bigger and others smaller as the logs reach specific gravity (G). You can see more in the ICC 400 Log Standards section 302.
Those checks can be seen exterior and interior, horizontal and vertical. While some see them as part of the log, others find them very displeasing. Besides the appearance there are some things that need to be addressed when checks are on the exterior of a structure. Foremost, upward facing checks are like gutters, collecting water in all its forms. This water becomes trapped and is absorbed in the wood fibers. It then starts to decay the wood internally where it can not be seen. Even if the logs look fine on the exterior, stain and sealers are doing their job. The hidden damages can cause expensive log replacement

Bigger checks of 1" or more I like to cut out a taper in the check. Using a small saw, I use a small electric chain saw. In which I cut tapers within the check making sure to go all the way to the very ends of the check. This is important as you can not caulk or seal those small ends properly. I do this for two reasons. One, to make a space for the wooden wedge I cut to fit the check. Two to cut out all the splinters to create a good fit for the backer strips required before caulking. On the job site I will use a 2X and circular saw set at angle to cut the wooden wedge. These I like to make a bit bigger so they extend beyond the log. That way I can grind off to fit. I fill the checks with either powder or liquid borates using a squeeze bottle. Like from a dish soap of ketchup bottle. I use glue to adhere the wedges. A good all weather adhesive I use is UltraTech 0770 ADA by Loctite. After the wedge dries is fully dried, grinded down and sanded. I can then match the stain and finish as needed.

For checks that do not need wood, proceed with the same method but use backer strips that fit the check. They come in many sizes. The use of backer is very important as it creates that all important two point adhesion that bonds much better and allows the product to stretch properly. If backer is not used product could pull from the wood and there is no mid point of expansion to stretch. Follow the curves of the check with the saw and backer. Again, don’t forget the borates. A proper backer in inserted in the check is 1/4'” – 3/8” below the surface of the face of the log. This gives a depth that will hold a good amount of caulk, but not wasting by using to much. Tool using water mixed with a little dish soap. You can use a small brush with hair or foam. Wipe any excess off with a rag wiping in the same direction each time. I like using caulk designed for applications I am doing. Textured products like Conceal have grits that make it much less noticeable when dry. Other caulks are very smooth, and wood is not so much. Colors change as they dry so always do a test area first. Stain can also be applied over these areas after proper curing.

Reprinted from 2019 GLLCA newsletter.