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STRUCTURAL INSPECTIONS & DEFECTS
ADVANCED INSPECTION METHODS
AGE of a BUILDING - how to determine
ARCHITECTURE, STYLE, & Building Age
DEFINITIONS of Mobile Home, Doublewide, Modular, Panelized
DEFINITIONS of ENGINEERED WOOD OSB LVL etc
FLOOR, ENGINEERED WOOD & LAMINATES
MOBILE HOMES, DOUBLEWIDES, TRAILERS
MODULAR HOME CONSTRUCTION
STAINS on & in BUILDINGS, CAUSES & CURES
WOOD STRUCTURE ASSESSMENT
This article provides a photo guide to determining building age by examining its structure. We describe building framing materials used in different epochs of residential construction. Knowing when certain materials were first or last in common use can help determine the age of a building. We list various kinds of building materials and give the history and dates of their first (and in some cases last) use in residential and light commercial construction.
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The age of a building can be determined quite accurately by documentation, but when documents are not readily available, visual clues such as those available during a professional home inspection can still determine when a house was built. Our page top photo shows modern floor framing details for a modular-constructed house.
See Framing Methods Age for the history and date ranges of various building framing methods. Also see Nails and Hardware, Age, Types and Saw Cuts, Tool Marks, Age of for additional building age clues likely to be available when examining building framing materials. Also see ARCHITECTURE & BUILDING COMPONENT ID.
The observation of framing materials, framing markings, and framing styles provides considerable information about the probable age of a house. We discuss framing materials and styles here as an aid to house age determination. Antique and modern trusses are distinguished and modern laminated beams and I-truss beams and wood joists are discussed.
At left our photo illustrates a modern (21st century) post-and-beam construction using milled timbers but traditional mortise and tenon and treenail connectors.
Asbestos-Cement Board & Fiberboard Products
Exterior Siding & Roofing Using Asbestos Cement included asbestos cement shingles, asbestos cement siding, corrugated asbestos-cement roofing.
Modern Cement Board & Fiber Cement Products
Cement board is a non-structural building sheathing material which in its contemporary form is made from Portland cement covered with a reinforced fiberglass mesh fabric. Cement board is used as a tile backer or a backer board for stucco applications on buildings. Current producers include Custom Building Products (WonderBoard™) and US Gypsum (Durock™).
Panels made of a mixture of cement and wood fibers are produced for building siding by James Hardi (Hardi-panel and Cemplank™), and CertainTeed (Weatherboard™).
(History & dates in process, contributions invited - CONTACT us)
Dimensional lumber that initially actually measured as equal to its nominal size (a 2x4 was actually 2" x 4") was produced beginning in 1833 in the U.S. (Augustine Taylor, building St. Mary's church in Chicago in that year) and was the dominant framing material in the U.S. by 1900. Our photo (left) shows the interior of a modern platform-framed structure going up in Minneapolis, MN in 2008.
The appeal of dimensional lumber was the reduced time and effort to construct a wood frame building compared with hewn timber frame beams that had to be cut and shaped, air dried for two years, and joined with mortise and tenon joints that required more highly skilled carpenters. Initially church members were concerned that their building was being built of flimsy too-small sticks and scaffolding materials.
The development of machine made nails that could be produced in high volume was critical to this change in construction methods. But even in the 1930's and 40's nails were a meaningful cost of construction. When our friend Paul Galow worked as an assistant to his uncle who built homes in Pennsylvania in the 1930's and 40's, his job was to salvage nails and hammer each bent one straight.
Our opinion is that modern dimensional lumber is not the same product as it was in 1833 or even 1940. Modern 2x lumber is produced from trees that have been developed to grow rapidly to a size at which they can be harvested.
Rapid tree growth means wide-spaced growth rings which means softer, weaker wood than dense-grained first-cut timbers or lumber.
That combined with the increasing number of knots (as 2x's are cut from ever smaller trees) means that the building frame must rely on additional materials (such as plywood or OSB sheathing) for a critical part of its strength. Or architects and engineers specify an engineered wood product such as a laminate-beam or wooden I-trusses or trusses where that strength is needed.
Our photo (above left) shows a modern laminated wood structural beam in both side and end view. (Make sure that your builder uses proper connectors and supporting posts, not the goofy structural setup in our photo). Our photo of I-joists (above right) shows this engineered floor support system in use in a Minneapolis home under construction in 2008.
In addition to plywood, OSB, and gypsum board, impregnated fiberboard has been used as exterior building insulating sheathing in North America since at least 1909 (see our discussion of Homasote, below and see Masonite™ and other hardboard Sheet and Siding Building Materials).
Fiberboard wall sheathing, when intended for use on a building exterior is installed by nailing directly to the wall studs, most often with let-in diagonal bracing or plywood panel bracing at the building corners to assure building rigidity.
There both non-structural and structural fiberboard panels that did not require this additional bracing have been produced. Some fiberboard sheathing products can claim adequate structural shear strength, particularly if the proper nails and nail pattern are used.
Other contemporary producers of fiberboard building sheathing include International Bildrite (Bildrite structural), Georgia Pacific (Stedi-R & Stedi-R-structural), Knight Celotex (Celotex premium insulating), and Temple Inland (Temple fiber brace).
Fiberboard sheathing, also called black board, gray board, or buffalo board sheathing in some areas, is a fibrous material impregnated with a stabilizer and water repellant - asphalt on early versions of this material that we have found. While it's not easy to find and identify this material on a building wall unless indoor or outdoor demolition is being performed, you can spot the product in building attics on the gable-end walls.
The R-value of fiberboard sheathing is higher than plywood, gypsum board, etc, and is rated at about R 2.4 per inch (or about R 1.2 in more typical half-inch thickness with which it is applied. The board also reduces sound transmission into buildings.
On buildings where gypsum board was used to cover walls or roofing, for structural stiffness we expect to find either plywood or let-in bracing nailed at the corners of building walls.
Initial versions of this product have not performed well on buildings where they might be exposed to dampness or leaks. We have found this material installed under asphalt roof shingles, hardboard siding, and other exterior siding materials.
Gypsum board continues to be marketed as a less costly alternative to plywood or OSB building sheathing.
These panels are intended for use under brick veneer and stucco exterior building wall finishes. Later versions of the material are called cementious board sheathing and can be expected to have been treated with water repellant chemicals.
Producers of gypsum panels used for building sheathing include Georgia Pacific Co. (Densglas gold™), US Gypsum Co. (Fiberock™), and National Gypsum Company (Gold bond™).
Our photo (left) shows a closeup of gypsum sheathing board used on building exterior walls and on some roofs.
Georgia Pacific's DensGlas™ exterior building sheathing includes this product description: "The product features a moisture-resistant core and enhanced fiberglass mats, instead of paper facings, to resist the effects of moisture exposure during and after construction.
It is so weather-resistant that Georgia-Pacific backs it with a 12-Month Weather Exposure Limited Warranty. " The company indicates that contemporary gypsum board sheathing such as their DensGlas™ product is intended to serve as a building " substrate behind brick, siding, EIFS, stucco and other permanent claddings."
Watch out: OPINION: unless your building is only expected to last 12-months, you should not leave gypsum board exposed to the weather. In fact few building sheathing products are intended to be left exposed to weather. For example, OSB sheathing board also deteriorates if it is repeatedly wet.
Hand hewn beams, chopped and then sized with an adze and axe were used in North America from the 1600's into the late 1800's. Our photograph at above right shows adze cuts and axe cuts that are normally visible in the rough surface of hand hewn wood structural beams.
Timber frame construction initially used hand hewn beams, cut roughly rectangular by an adze and axe. Later beams were sawn manually or mechanically by a manually operated vertical pit saw, ultimately by machine-powered pit saws and circular saws. Timber framing using post and beam construction with mortise and tenon joint connections was used in Europe for at least 500 years before it was first employed in North America.
Our photo at above left shows typical roof framing on a Poughkeepsie home built ca 1790. Notice that there is no ridge board or ridge beam used, just a treenail-joined pair of numbered saw-cut rafters. The timber framing shown in our photograph at above left is from an 1875 Colonial home in Newburgh, NY. You can see this house at ARCHITECTURE, STYLE, & Building Age.
For details about post and beam construction methods see our full text article at Post & Beam Construction.
By 1650 a typical timber frame building used multiple bents and girt beams, may have been more than one story tall, and included an exterior made of horsehair-reinforced cement stuccoed over hand-split lath. Timber framing in North America continued until about 1920. (CF Reference due: Age of Barns, op.cit.)
Identifying Photographs of Homasote®, Celotex®, & Similar Fiberboard & Insulating Sheathing Board Products
Insulating building sheathing made by Homasote® is produced by the Homasote Company, a manufacturer in the U.S. in New Jersey, and similar fiber sheathing products have been used both as a sound barrier and for exterior sheathing on buildings. Insulating board sheathing has been widely used on building exterior walls, under roofs, and against masonry foundations in finished basements.
Originally, Homasote produced sanded "agasote" sheets used in the roofs of passenger railroad cars, moving, in 1915, to automobile roofs, and in 1916 to construction products. Homasote was widely used for military barracks in both WWI and WWII and is still promoted for sound resistant sheathing and other applications.
Homasote and similar insulating building sheathing board products are still sold as a lower cost alternative to plywood or OSB for building sheathing. The product is used as structural paneling, insulation, concrete pouring forms, and expansion joints.
Our photos (above left and right) show closeups of Homasote-type insulating building sheathing board products, including a torn cross section showing the layered fibrous character of this material.
Where structural shear strength is needed by using the company's recommended ring-shanked nails in a specified nailing pattern. Homasote Co., the oldest manufacturer of building products from recycled materials in the United States, was founded by Eugenius Harvey Outerbridge as Agasote Millboard Company, and has been producing this material since 1909. In 1936 the company changed its name to its best known product, Homasote.
Our photographs below show Celotex® insulating board with an older Celotex fiberboard building sheathing board at left and a more recent Celotex insulating board product shown at below-right. Also see this closeup of an older Celotex insulating sheathing board product.
Antique Log Home Construction
(1640 - est U.S.): solid logs usually felled and prepared at or close to the building site, set on ground level, on flat stones on ground, or on a stone foundation, corners joined using various notch and overlap methods.
Our photo (left) shows traditional hand hewn logs and a log joint on a Norwegian cabin outside of Oslo.
Modern Pre-Cut Log Home Construction
Typical modern log homes use 6" or larger diameter factory milled logs that are cut to precise dimensions and whose design includes interlocking splines and gaskets to protect against leakage. In our photo (left) you can see the notches on the log bottoms and the log-end profile shows the raised splines on the top of each log.
See Home Buyers/Owners Guide to Log Homes for complete details about log home types, construction methods, inspection procedures, common defects.
See Slab Log Cabin Siding for a description of conventionally framed homes with a log-exterior.
Also see Log Home Construction for a brief description of this construction method.
Here is our complete list of log-home information, inspection, diagnosis, repair, construction, articles:
LOG HOME ENERGY EFFICIENCY
(History & dates in process, contributions invited)
Our photo (left) shows the back side of an early hardboard interior-use product labeled "Genuine4 Masonite Quartrboard".
What is the difference between waferboard and OSB?
OSB is a modern wood product that developed from earlier 1970's "waferboard" product. In 1990 the Structural Board Association was formed. By 1996 there were 38 OSB producers in North America.
Unlike waferboard whose composite wood chips were place randomly, an oriented strand board product is made from wood chips that are deliberately oriented with respect to one another to provide greater strength.
See SHEATHING, OSB for more details and photo examples of OSB Oriented Strand Board sheathing use.
CONTACT us to contribute photographs of waferboard or OSB.
Plywood Sheathing on Walls & Roofs: Use in Building Construction, History, Description, Identification
PLYWOOD Roof, Wall, Floor Decks & Sheathing (1905 - present as a construction material in North America) is sheet material made of thin veneers of wood that are laid with wood grains in alternating direction, glued, heated, and pressed together.
Our photo (left) shows both fire-retardant plywood roof sheathing (left half of the photo and center top and bottom) and OSB roof sheathing (center of photo and right edges of photo).
While modern plywood products use a variety of glues, heat, and pressure to produce the product, plywood has been around at least since 3500 BC when a glued-veneer version was produced in Egypt.
The rotary lathe (ca 1850) made modern plywood possible by cutting large sheets of wood from logs. The sheets are at right angles to one another and glued together using interior or exterior-rated structural adhesives. Interior plywood is generally glued with urea formaldehyde based glues; exterior plywood and marine plywood use phenolic formaldehyde glues and are water resistant.
Also see FIRE RETARDANT PLYWOOD.
Details about wood roof and floor trusses are found at TRUSSES, Floor & Roof. Excerpts are below.
Wood Floor & Roof Truss Photos
Our photos show an attic view of modern roof trusses (above left) and floor trusses (above right).
Truss uplift, a cosmetic not a structural defect, is discussed separately at TRUSS UPLIFT, ROOF
Metal Floor & Roof Trusses
Details about metal roof and floor trusses are found at TRUSSES, Floor & Roof. Excerpts are below.
Steel roof trusses do not "rot" of course, but they too are vulnerable to damage from water, leaks, and rust.
Below our photo shows steel I-joists used in floor structures.
Welded-wire sandwich framing panels: polystyrene or polyurethane foam core insulation is surrounded by a welded-wire space frame.
(History & dates in process, contributions invited)
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Frequently Asked Questions (FAQs) about building framing & sheathing materials
Question: Question about Homasote product from 1940s. Mold problems on gypsum board exterior building sheathing? Asbestos in exterior gypsum board sheathing products?
f it is still on the house, could it contain asbestos and/or contain mold due to lack of sunlight?
Was there "code" at some point that would have forced individuals who were to replace vinyl siding on the house over these boards to replace with proper products after a certain date? Thank you, K.B.C.
Reply: Properties of Homasote® type fiberboard compared with gypsum-based exterior wall & roof sheathing boards
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with sheathing, leaks, and mold or asbestos sources in buildings - the concerns you expressed. That said, here are some things to consider:
Homasote® fiberboard sheathing is a wood fiber product, not a gypsum or plasterboard product. However there were indeed gypsum-based sheathing board products used on buildings both as wall sheathing (under siding and over studs) as well as roof sheathing. Having inspected quite a few buildings that used this material, my OPINION is that it has proven surprisingly durable so long as it was kept dry. Wet the material can become soft, and also one might find mold growth on the paper backing of the gypsum board.
We describe these two different product types at Sheathing, Gypsum board and at Sheathing Celotex Homasote & Other - a section of FRAMING MATERIALS, Age, Types where we describe the history of building framing and sheathing materials.
Some Gypsum board and plaster board products indeed contain asbestos as does some joint compound
Indeed some gypsum--based drywall products did contain asbestos into the 1980's. I have not, however, tested nor seen test results specifically for exterior wall sheathing using that material. I suggest sending a small sample, a square inch would be plenty, to a certified asbestos testing lab - the cost should be less than $50. Do let me know what you find as the results will be helpful to other readers.
Even when gypsum board or plaster board did not itself contain asbestos, some joint compounds did contain that material right up into the 1980's. But used as an exterior sheathing, at the buildings I've seen, there was no top coating of joint compound and tape on this type of sheathing board (as there would be on drywall used for interior wall coverings).
Mold growth on gypsum board building sheathing?
About mold growth: the simple absence of light is not sufficient to cause problematic mold growth in building cavities. Water or high moisture would be a requirement for nearly all indoor mold contamination. And indeed I have found mold growth on paper backer on plaster-board exterior wall sheathing, in the wall cavity in buildings where there had been leaks into those spaces.
So if your home's walls were leaky (from ice dam leaks at the eaves, from leaks around windows or doors, from wind-blown rain penetrating damaged siding, etc) then there might be problematic mold growth on those surfaces - in the previously or currently wet areas. Whether or not this problem deserves investigation and remediation is not something one can decide without more detailed information.
See MOLD EXPERT, WHEN TO HIRE for help in deciding if in your particular case hiring a competent professional to inspect and test the building is justified.
Requirements to Remove Old Siding & Sheathing When Re-Siding a Building?
Finally, I've not found any national building code that requires a homeowner to replace one existing siding or wall sheathing material with another. The decision on siding-over existing surfaces vs. doing a (more expensive) tear-off depends on at least these considerations:
Watch out: be careful not to add multiple vapor barriers to a building wall. Installing an air and moisture resistant vapor-permeable housewrap should be fine however, and is required by some building codes and some product manufacturers.
Questions & answers or comments about how to determine the age of building framing and sheathing materials, a step in determining the age of a building or of building components, systems, styles, and architectural design
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