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Simple clues to determine the age of an old house

Whether you considering purchasing an old house, or you already live in one, it’s fun, not to mention useful to know some of the major clues that can reveal when a house was built. Keep in mind though that dating old houses is an inexact science. Just as electrical service came to different areas at different times, so did changes in architectural styles and construction methods.

Also, many older homes have been renovated over the years and the newer features can throw you off. For example, I lived in a house that had beautiful chestnut moldings downstairs in a style that wasn’t available until the 1880s. Upstairs moldings were plain boards. This could simply have meant that the builder saved the more costly fancy stuff for the public spaces. But it made me suspicious, and indeed other construction materials and methods and the overall architectural style of the house made it much more likely the house was built in the 1860s.

So, dating an old house is a matter of time bracketing. By looking at the way the lumber was sawn, how the nails were made, the type of moldings, the architectural style and other factors, and then correlating the time periods during which each element was popular, we can narrow down the time period during which a house was built. This means that the more you know about the elements of home construction, the more you can zero in on a date.

For now, just to get you started, I’ll touch on how to date two major elements of home construction—the lumber and the nails. You can find evidence of these in the exposed framing of the cellar and attic.

Timber frames

Before around 1860, houses were typically timber framed--unless they were made of masonry. Timber framing takes quite a bit of skill. Large timbers are joined with tenons fitted into mortises. Then a hole was drilled through each joint and a wooden peg was driven into the hole to lock the two framing members together. Below is a drawing of a typical timber frame.

There were three methods of cutting the timbers to size. Hand-hewing and pit-sawing were most common. The third method, water powered sawmills existed in North America as early as 1620 but they were uncommon. You needed a swift stream to run the mill and you needed enough nearby population to make the mill economically feasible. It wasn’t practical to transport big timbers long distances.

Hand hewing was done with a special axe called an adze. Unlike a typical axe, the cutting edge on an adze is perpendicular to the handle. The worker straddles the log and swings the adze toward himself, cutting out a chunk of wood with each blow—and yes it’s as dangerous as it sounds. Hewing left the marks you see above.

Rather than the adze marks left by hewing, some early timber frames have straight saw marks across the width of the timbers. If pairs of marks cross each other at an angle, then the timber was pit-sawn as shown at right. One man stood in a pit under the timber and the other stood on top. Together they worked a long two-handled saw back and forth. Angling the cuts is a more comfortable motion, plus it prevented the sawdust from falling directly in the bottom guy’s face. If saw marks are straight up and down with regular spacing, the timber was cut at an early water-powered mill as shown below.

Stick Framing

As I mentioned, milled lumber was pretty rare before 1860. Then around that time, steam-powered mills using circular saw blades came on the scene. This made it feasible to slice lumber into smaller pieces and so stick framing was developed. By the 1880s stick framing was the mainstream way to build a house. During this period the advent of railroads made it feasible to ship lumber around the country.

The earliest form of stick framing was called balloon framing. Balloon framing was used until around the 1940s when platform framing took over. Platform framing is still used today.

The drawing at right shows the difference between balloon and platform framing.

In balloon framing the 2x4 studs ran from the sill to the top plate under the rafters. The big problem with this was in the case of fire, the flames would quickly be sucked up the uninterrupted wall cavities. Platform framing is so named because you started by building a platform for the first floor, and then built the first story walls on top of that. Then you built another platform before erecting the second story walls. The second platform acts as a fire stop. Also, it gave carpenters a secure platform to stand on while putting up the second story walls. Plus, shorter studs were easier transport and work with.

Most of the sticks in stick framing are "two-bys"—which, until 1920, meant they were two inches thick. So if you go in the cellar or attic and find joists that are a full 2 inches thick, the house likely was built between around 1880 and 1920. In the 20s, most lumber manufacturers began planing lumber to final dimension, so the circular saw marks disappeared and lumber became smoother. They were planing down 2x4s so the final dimensions were smaller—about 1 ¾-inches thick until 1962 and about 1 ½ inches thick today. That’s why today’s 2x4 actually measures 1 ½-inches by 3 ½ inches.

One more thing that’s important to know when using lumber marks to date a house—Old hand-hewn beams were quite often reused in newer structures. Usually it’s easy to tell—there will be other members that are sawn. Plus you’ll usually find unused mortises along the length of the piece.

The picture at right, taken in my basement, shows a mixture of lumber from various eras. To the right, two hand-hewn beams are mortised on the ends to fit over a tenon in a hand-hewn post. To the left of that a sawn beam sits atop a post with curved marks indicating it was milled with a circular saw blade. Our first thought might be that the the second post and beam were added later as reinforcement. I doubted it-- other features of my home don’t seem to date that far back. And looking a little further along the beam, confirmed my doubts: Shown below is an empty mortise in the same beam. You can see the hole drilled through both sided of the mortise where it would have locked the tenon in place.


I am just going to brush the surface here and discuss the three major ways nails were made. There were more subtle changes that can help you more closely narrow down a house’s age—if you are interested you’ll find lots of great information online.

Hand-forged iron nails, shown at right, date back thousands of years. They were labor intensive to make—it took a lot more blows with a blacksmith’s hammer to make a nail than it took blows of a carpenter’s hammer to drive one into wood. And of course you needed a forge. As a result, nails were expensive and hard to come by in colonial America. In fact, nails were so valuable that unused buildings were sometimes burned down so the nails could be retrieved. That is, except the nails used to make doors. Early doors consisted of vertical planks held together with a horizontal plank near the top and one near the bottom. Opening and closing doors could loosen nails, so carpenters drove long nails though so they stuck out the other end, and then cinched them over. Of course this meant the nail couldn’t be reused. That’s where we get the expression: “Dead as a doornail.”

Hand forged nails were used until about 1810. They are easy to identify because they are irregular in shape and have roundish heads. Some had narrow T-shaped heads, or less often, L-shaped. These were early finish nails, designed to be inconspicuously driven below the surface.

Now here’s the tricky part—from the 1790s to the 1890s, many nails had hand-forged heads attached to a machine-cut body, so it’s hard to date them in place just by looking at the heads. Shown at right, these were called cut nails because their shanks were cut from flat sheets of iron. After the 1890s machines to create so-called “wire nail” were developed and nails got a lot cheaper. Wire nails, still used today, have round shanks and nearly perfectly round heads.

The interesting thing is cut nails hold better than modern round nails. This is mostly because they are tapered, which creates a wedging action. So machine-made cut nails, shown below, are still available today. They are often used to install plank floors. You can identify them by their smooth, regular square heads.

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