Log Home Inspections

The term “structural failure” brings to mind visions of crumbling and collapse of the home foundation, walls and roof which would be called “catastrophic failure”. By far the most common type of structural failure is slow, long-term failure which takes place over years rather than in a few moments.

Part of an inspector's job is to recognize and comment on signs of existing failure, allowing their client to negotiate for corrections and preventing future damage. Sometimes, no signs of failure may be visible at the time of the inspection, especially in newer homes. In these situations it's up to inspectors to recognize conditions which will eventually cause failure if not corrected.

The forces which typically cause failure in log homes are the following:

• Soil movement
• Decay
• Wood-destroying insect activity
• Poor construction practices (design, materials or workmanship)
• Log movement

SELLER INSTRUCTIONS

Because of the many variables and liability inherent in log home inspection, we will make every effort to create a list of documents to be made available by the seller for examination by the inspector during the inspection. These might include documents showing...

• the name of the original builder.
• proof of certified log grading.
• written settling adjustment records.
• any special systems installed but not visible at the time of the inspection.
• any performed maintenance.
• additional construction or repair since the original construction.

  TREE NAMES

  Trees have two sets of names.

  • Scientific names (also referred to as Latin names) are designed to separate tree species according to differences in their physical components such as leaves, cones, bark, flowers and wood structure.
  • Common names are the layman's terms used more often, which can be misleading. Common names for the same tree species sometimes change from one area to another. Sometimes one common name is used to describe wood from several tree species with very different properties and appearance.

  For our purposes, the following list of tree species typically used for log building in North America gives both scientific and the common names which we’ll use throughout the course. Inspectors will find buildings constructed from additional species not included here.

  COMMON NAME/LINK	SCIENTIFIC NAME
  Cedar, Western Red	Thuja plicata
  Cedar, Atlantic White	Chamaecyparis thyoides
  Cypress, Bald	Taxodium distichum
  Fir, Douglas	Pseudotsuga menziesii
  Pine, Lodgepole	Pinus contorta
  Pine, Red, Norway	Pinus resinosa
  Pine, Ponderosa	Pinus ponderosa
  Pine, White	Pinus strobus
  Pine, Yellow, Longleaf	Pinus palustris
  Redwood	Sequoia sempervirens
  Spruce, Engelmann	Picea engelmannii

  Source

  Links in the table above give detailed information each tree species.

  TREE TYPES

  Seed plants, including trees, are divided into two classes: gymnosperms and angiosperms.

  Gymnosperms: Softwoods, mostly coniferous (don’t drop needles in the fall), provide the logs from which most log buildings are constructed. A few exceptions, such as larch (tamarack) and cypress, do drop their needles in the fall.

  Angiosperms: Hardwoods, mostly deciduous (do drop their leaves in the fall) such as oak and walnut are occasionally still used by builders.

  The terms “hardwood” and “softwood” don’t correspond to wood density. Some softwoods (Douglas fir) are harder than some hardwoods and some hardwoods (Balsa) are softer than some softwoods. Almost all softwoods are evergreen trees with needles instead of broad leaves.

  Because the vast majority of logs used in building log homes come from softwood trees, this course will concentrate on softwoods.

  TREE COMPONENTS

  Any plant species which grows taller than 20 feet when mature and has a dominant single stem (i.e., the tree trunk) can be referred to as a “tree.”  Plants which mature at less than 20 feet are called shrubs and aren’t used for building.

  

  Source

  Trees trunks divide into limbs, which divide into twigs. Trunks, limbs and twigs all have the same general structure. Starting from the outside:

  • Bark
    • Outer bark is composed of dead cells, and protects the tree internal structure from fungi, insects, animal or mechanical damage, weather and fire. Bark is not considered to be wood.
    • Inner bark is composed of live cells called “phloem” through which food is transported from leaves to parts of the tree where growth takes place. This includes the tips of roots and twigs and the cambium layer of trunks and branches.
  • Cambium refers to a thin cell layer which produces new wood cells, from which all growth in trunk thickness takes place and which separates bark from wood.
    • New cells produced toward the exterior of the cambium layer (cork cambium) first move outward to become phloem, which is alive, and then become bark, which is dead.
    • New cells produced on the interior of the cambium layer (vascular cambium) become sapwood, which eventually becomes heartwood.

  Wood is divided into two types, both of which (in North America) exhibit annual growth rings, but which perform different primary functions in the tree.

  • Sapwood helps to support the tree, but its main function is to transport water and mineral nutrients from the soil to leaves. Its cells also store carbohydrates and provide protection. Typically light in color.
  • Heartwood is composed of dead cells and is a main source of structural support. Heartwood cells also store extractives (including toxins) safely. Extractives give heartwood its typically darker color.

  Other important parts of the tree interior:

  • Pith is composed of a soft wood which forms the center of the tree.
  • Extractives are various organic and inorganic chemicals found in cell walls and cavities, especially in heartwood. Comprising 2% to 15% of wood's dry weight, they contribute to wood's color, odor, taste, density, hygroscopicity (ability to absorb water) and flammability, but most important to the log home industry is that because some of them are toxic to decay fungi, extractives help prevent wood decay.

  Extractives include tannins, oils, lignins, fats, resins, waxes, gums, starch and terpenes. They're called "extractives" because they can be extracted from wood by heating it with water or a solvent. Extractives have commercial value.

MODERN CHINKING CONSIDERATIONS

Many defective applications are not visible until they fail and confirmation of proper chinking methods connected with these conditions should be disclaimed by inspectors in the report and explained verbally to the client.

• Two-point adhesion- To allow maximum flexibility, chinking should be adhered to both upper and lower logs, but should have a middle section of uniform thickness which is free floating- not bonded to wood. This is usually achieved by installing foam backer rod or plastic tape into the joint between logs before chinking is applied. Proper application may be difficult to verify visually.
• Blistering- Improper backing materials such as colored foam boards or extruded polystyrene can cause blistering. Excessive moisture in the logs can also cause blistering.
• Telescoping- poor backer material installation can show through once the chinking has cured.
• Thin application- Chinking applied too thinly will tear. This is sometimes a problem where round backer rod has been used. A good rule of thumb is 3/8” minimum thickness. This is often difficult to confirm. Tears less than a foot long can be caulked. Tears exceeding one foot should have chinking cut out and replaced.
• Inadequate bead width- A good rule of thumb for the width of the chinking bead is 1/6 of the log diameter. An 8” log diameter would be calculated like this (8 ÷ 6 = 1.3”   (1  5/16 in. wide chinking bead). A home with significantly smaller beads throughout should be brought to the client’s attention with a recommendation for a specialist evaluation.
• Incompatible finishes- Some adhesion failures can be caused by the application of chinking to a log finish with which it’s not compatible. Logs with oily or waxy surfaces do not allow for a good bond with chinking sealants. Inspectors need not give reasons for adhesion failures, but only state that they exist, and recommend a specialist evaluation or repair by a qualified contractor.
• Tooling- Tooling the chinking bead compresses it to the wood surface and helps ensure a good bond at the bead edges where the chinking is thinnest. Untooled chinking should be called to the client’s attention as possibly shortening the lifespan of the chinking system.
• New chinking bonded to existing mortar- Although it’s not recommended, new chinking applied over existing mortar is not in itself a defect. However, a bond-breaker such as plastic tape must be applied to existing mortar and areas of missing mortar must have a backing material installed. Both these conditions will be difficult for inspectors to verify and are one more reason to disclaim hidden chinking conditions.

The following disclaimer would be included in homes with chinking installed…

Evaluating Log Finishes

Home inspectors are typically not present when old finish removal and re-application or the original application are performed. Because improper procedures followed during finish removal, surface preparation and finish re-application may not be readily discernable through a visual inspection by a general home inspector, Inspectors should disclaim proper application procedures.

Inspection Contract and report language should make it clear that the scope of the inspection is limited when inspecting finishes:

• The Inspector is not required to identify the finish coating type.
• The Inspector is not required to identify the cause of any finish failure.
• The Inspector is not required to confirm proper removal, preparation for or application of finish coats.

Sample Disclaimer

“The result of any improper procedures followed during finish removal, log surface preparation for and/or application or re-application of finish coatings may not have been readily discernable through a visual inspection at the time of the inspection. The General Home Inspection is limited to log finish coat condition and defects visible at the time of the inspection only and the Inspector disclaims confirmation of the proper finish removal, preparation for, application or re-application of the finish coatings in place at the time of the inspection.”

COMPLIANCE WITH CODES AND STANDARDS

Confirming compliance with any building codes or standards relating to log home construction which are set forth by any agency, organization, council or association lies beyond the scope of the General Home Inspection or Log Home Inspection.

COMPLIANCE WITH ENGINEERING OR MANUFACTURER’S SPECIFICATIONS

Because there exists a multitude of log home builders offering both manufactured and handcrafted homes, each using a method often of their own choosing and invention and often requiring that the contractor building or assembling the home adhere to a similar multitude of proprietary engineering specifications, the adherence to most of which cannot be confirmed without disassembly of the relevant home component, inspecting for compliance with any Manufacturer’s Building or Engineer's Specifications lies beyond the scope of the General Home Inspection or Log Home Inspection. This includes any systems or components designed to accommodate or adjust for continual settling of logs in log walls.

FINISH COATING INSTALLATION

Confirming proper preparation for installation or any installation of any log finish coating, both interior and exterior, would require examination prior to or during the installation of such finish coating, and as such lies beyond the scope of the General Home Inspection or Log Home Inspection.

HIDDEN WOOD DECAY

Although the Inspector uses techniques such as probing and visual examination in an effort to determine the presence of wood decay in the logs of log structures, these techniques are not technically exhaustive and will not reveal the presence of wood decay hidden in inaccessible places, such as log cores and/or the intersections of log walls. For this reason, locating or identifying wood decay which is not readily visible or decay of logs in inaccessible areas of log homes lies beyond the scope of the General Home Inspection or Log Home Inspection.

INSECT INFESTATION

The Inspector is not qualified to perform inspection for wood-destroying insects and specifically disclaims any infestation. The Inspector recommends that the Client have the home inspected by a contractor qualified to perform this specialized inspection.

PROPER CHINKING INSTALLATION

Confirmation that proper preparation and installation of chinking designed to seal gaps between logs would require examination prior to or during installation and the Inspector specifically disclaims any chinking defects not readily visible at the time of the inspection.

SETTLING AND SEISMIC ACCOMMODATION