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How To Determine The Age Of A Building

We all love to ask: how old is this building?


Without precise documentation outlining the details of construction, the answer can sometimes seem like a shot in the dark. Yet, with a little bit of detective work, there are a few subtle ways to determine the age of a building, as well as its various vintages of renovations.


The easiest and most obvious method of dating a building is a large date stamped in concrete across a building's face. Occasionally, this stamp exists hidden behind an exterior facade in favor of modern upgrades. In this case, the building owner wanted to highlight the building's history while giving it a cosmetic makeover.

Similarly, some buildings have time capsules with dates embedded into the building walls. You can also check for dates scratched into concrete paving. This is a method best served to determine when the concrete was poured rather than a finite age of a building.


A better method is to take a look at various building components to determine their age of manufacture and thereafter estimate their date of install. A glance into the interior bottom of each window will reveal a code and likely even a clear date of production. It is best practice to date multiple windows to ensure the general age is accurate and exclude any windows that may have been recently replaced. In particular, the largest windows are the best indicator as they are the most expensive and time-consuming to replace.

Other great indicators are the HVAC unit serial numbers. As not all buildings have air conditioning units, the furnace is the best indicator. Using its serial number and online manufacturer resources, you can easily determine the date of production and shortly thereafter the time of install.

Similarly, another indicator lies in the building inspection records found on HVAC Units, framing, plumbing, and life safety systems. These records sometimes show a history of vintages between construction and upgrades. Tracing through these inspections will reveal the earliest point of inspection which is likely also the initial inspection post-build.


Newer homes have date stamps on building materials which are not always accessible post-construction but with some sleuthing can tell you a lot. Plywood and oriented standard board (OSB) used as roof underlayment often has the date stamped on the underside which often is visible in open attics. Electrical wiring also has date stamps and while typically buried within walls, can sometimes be visualized in unfinished basements or leading through or above cabinets. Materials without clear dates can also be decoded by manufacturers.

Characteristics of older homes sometimes give away the age of the home. Sears catalog homes were sold from 1908- 1942 and constructed as late as 1946 depending on how long it took owners to construct their homes. Wartime homes built for families assisting the war effort in the 1950s and 1960s have a distinct box-like style and they line their neighborhoods in neat rows.


Older homes built from 1920 to 1950 also have knob and tube wiring. You can tell if you have knob and tube wiring by taking a peek at the floorboards from the basement. White ceramic knobs are nailed to the joists with electrical wiring running through the knobs that prevent them from touching the floorboards. This style of wiring is often replaced in favor of modern wiring, but the porcelain knobs or at least their holes remain as an indicator of age.

Sewer infrastructure is a good indicator of when the neighborhood was developed. If your building is similar to those around it, likely they were built around the same time. Sewer grates, manhole covers, and fire hydrants are often dated, giving you a general idea of when construction may have begun on your building.

Finally, home warranties are often provided with stickers attached to an electrical panel or near it on cabinet doors or framework. If you have retained this document and the date of construction is unclear, you can utilize the contact information to decode the enrolment number and get the exact date of construction.

Cross-referencing all of this information can help you form an idea of when the home was constructed. If the data proves to be inconclusive, at least you now have an idea of when renovations occurred!

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