The hardest house to date is a link home. They appear to be single, but if you do some digging they're actually attached.
Home inspectors have some tricks for figuring out the age of a house. In newer subdivisions they pick up dates from manhole covers, sidewalks, and curbs. This will give you an idea of when the subdivision was built. This obviously doesn't work in older neighbourhoods.
Thermal pane windows usually have a metal strip which separates the two panes of glass. On that metal strip you will often find the manufacture's name, a CMHC number, and the date of the manufacture. Again, this information must be used carefully. It will tell you the age of the window but not necessarily the age of the house. Check several windows. If they are all the same, you have just figured out how old the house is or the date when all the windows they're upgraded.
On houses built within the last 20-25 years, you will often find a sticker on the outside of the electrical panel indicating the possession date of the house. The Ontario New Home Warranty period could easily be established.
If you can be sure that the furnace of the water heater is original, the gas inspection sticker on either of these appliances is a good indication of the age of the house.
Porcelain plumbing fixtures usually have a manufacture date stamped into them. The easiest place to pick up a date is off the toilet (no joke). If you remove the lid from the tank, the date will often be stamped on the underside of the lid and also inside the tank near the water line. The date is usually on the right hand side of the rear portion of the tank when you are facing the toilet. The date inside the tank is more reliable than the date on the lid because sometimes lids get broken and replaced. Again, you must look for other clues to convince yourself that the toilet is an original one. Otherwise, you have only established the date when the bathroom was renovated.
Certain building materials can be clues about the age of the house. These clues can vary dramatically by region. For example, in Toronto, virtually all houses with stone foundation walls they're built before 1930. If you go to Kingston, Ontario, however, and ask when they stopped using stone foundation walls, the response might be "You mean they stopped using stone foundation walls?"
In Toronto, brick foundation walls were also popular until about 1935. In other parts of the province, you will find no brick foundation walls at all. With the exception of custom built houses, most houses built with concrete block foundations are pre 1970. Most subdivision houses built in the 70's or newer have poured concrete foundations.
Most brick houses in Ontario were solid masonry construction (two types of brick) up until the late 1960's. Most brick houses built after 1970 were brick veneer construction (one tyoe of brick with a wood stud wall behind).
If you stand in an unfinished basement and look up at the subflooring, you will find that most houses before 1965 used plank subflooring. After 1965, most houses had plywood subflooring, until the early 1980's, when wafer board subflooring became popular (with the builders at least).
Aluminum wiring began to be used residentially in about 1965, however, it did not really catch on until about 1970. When was it banned? It was never banned, however, it received so much bad press, that aluminum wiring stopped going into houses about 1978. To this day, aluminum wiring is still used to bring power into the house form the street.
Knob and tube wiring was superseded by conventional modern wiring in the late 1940's. Even though wiring looked modern through the 1950's, it was not until 1960 that modern wiring contained a ground wire. Therefore, houses built before 1960 have two prong outlets as opposed to modern electrical outlets which are designed for three prong plugs.
Before 1950, supply plumbing was galvanized steel. Houses with galvanized steel supply plumbing also tended to have cast iron waste plumbing.
In about 1955, waste plumbing was more likely to be copper went through the roof. Waste plumbing very quickly became plastic. (It was this jump in the price of copper that also lead to the use of aluminum wiring.)
Old houses have plaster on the walls and ceilings whereas new houses are built with drywall. When did the change occur? While there was no magic day when plasters quit and drywallers began, most houses built before 1960 were plaster and most houses after were drywall.
Dating houses can be helpful for a number of reasons; for example, the type of furnaces installed 20-25 years. Therefore, most houses built in the early 1970's have a new furnace or will need one shortly. Most houses built in the early 1980's were built with asphalt shingle roofs that lasted up to 15 years. Again, most of these houses either have a new roof covering or need one. The good news about a 1982 house in need of new shingles is that it couldn't possibly contain Urea Formaldehyde Foam Insulation. It was banned in December of 1980!