How Buildings Work

Gas Lighting

We are afraid of the dark. We don’t like it. For thousands of years we have worked on having mastery over our surroundings, and the production of light has been a crucial instrument all along the way. We created fireplaces and elaborate urns, then progressed to candles and eventually burning oil lanterns. The biggest drawback for all of these methods when it came to household illumination was the constant need of refueling. With natural gas, this changed.

In the Knob and Tube post, there is a reference to dual source light fixtures, the other source being coal-gas (and eventually natural gas). Originally discovered as a byproduct of coal mining, this invisible gas quickly became adopted as a light and heat source once it’s benefits were understood.

Paris and London were some of the first cities to use gas lighting for public places and streets. Having a gas that could be distributed via pipes allowed for illumination of much larger spaces with significantly reduced labor. Theaters saw widespread use, becoming so bright now actors and actresses had to change their makeup and motions of acting, able to be seen much clearer now. The Chatelet Theater in paris boasted over 28 miles of piping and over 900 valves for control.

Raw flame was a significant step above candlelight, but pioneers didn’t stop there. By aiming the jet of fire at different materials, even brighter light could be generated. Popular in theaters, a metal mesh coated with lime would yield rather brilliant light, hence the phrase “being in the lime light”

In buildings, the gas is distributed via cast iron pipes with threaded connections. While labor intensive, the ease and shorter learning curve led with widespread adoption. Combined with the cost savings over traditional fuels, and the struggles with electricity distribution, gas remained popular as a lighting solution well past the first electric lamps. Another added benefit was being able to use the same gas for heating devices, as well as cooking and baking. It is little wonder it took large leaps in electrical technology to finally end gas’ reign.

So why don’t we use natural gas more often today? Compared to modern wiring for electrical power distribution, gaslines are much more labor intensive to install. Some modern developments have narrowed the delta a bit, but electrical power is far more prevalent. The visible risks, fire and explosions, have plagued natural gas since it’s infancy, blamed for burning down countless buildings. Now that we have a great understanding of natural gas, we know that burning it creates large amounts of carbon monoxide. Drafty homes in years past kept this from becoming a widespread killer, but today incredible precautions and safety enhancements are needed to keep this poisonous gas at bay.

While it’s (and near cousin, propane’s) portability in tanks still allows for convenience in remote areas, we rarely see gas lighting today. It’s greatest use is in heating of air and water for domestic heat, and many still prefer cooking and baking with it in the kitchen. Decorative fireplaces have also seen a lot of popularity as safety mechanisms increase their reliability in the home.

How Buildings Work

More on Electricity

Coming back from a recent trip to Europe of course leads many questions about the differences in infrastructure and building development. It’s amazing how different things are across the board; electrical, plumbing, building materials, etc.

In doing research on these variations, I stumbled across a good read over at Rexophone. Good in this case being lengthy and nerdy, but also full of interesting photos as we discovered how to make electricity work. It’s a good resource for some of the items talked about in the Knob and Tube post. In particular, the photos of household items before plugs were invented are spectacular.


How Buildings Work

Plaster and Lath

These two words get thrown around a lot with older buildings. And while someone may recognize a photo of a wall built this way, there is a whole world of history, maintenance and repair that are often glossed over.


Early human built structures relied upon the materials of the structure for the finish. Think log and stone cabins; What you see is what you get–on both sides. As our massive brains figured out more materially and labor economical ways to construct spaces, timber/lumber and bricks being the most popular, we lost the benefit of having a pre-finished interior surface. Even with a lot of early structures, there was still a desire for a different surface treatment on the interior. This is where plaster came in.

A mixture of lime with sand and/or cement creates the variety of plasters out there. When used on the exterior of the structure, it then becomes stucco. Depending on the desired finish and location of use, the ratios of these materials may change. Fibers, often horsehair, would be added regularly to help improve strength of these coats.

With solid stone or brick construction, it is easy to apply plaster directly to the construction surface. Once you move to a frame based construction, your home is now filled with large gaps that must be overcome. Solid wood, as you could imagine, would be very expensive. So a product of economic and functional forces was: lath. Thin strips of wood would be nailed to the lumber to create a semi-solid surface that plaster could be applied to. Voila!


Once the lath was nailed in place, plaster would be mixed on the spot, and applied directly to the lath. This is where varying the mixture of plaster becomes important. This first layer would have more sand and other binders in it to help it stick to the lath. The spacing of the lath was also key, allowing some of the plaster to flow between the slats. Once hardened, these extruded pieces are referred to as keys. This is where the strength (or weakness, as we will see) of a plaster wall originates.

Once this base coat is complete a finish coat, or two, would be applied. Frequently vertical guides would be installed to ensure a flat and square surface. Since most houses with plaster and lath were built before standardized dimensional lumber, there would be variations from stud to stud. This application method made it easier to absorb these differences into the thickness of the plaster being applied.

Beyond making up for wall thickness variations, plaster and lath application afforded many other opportunities. Curved and decorative surfaces were significantly easier to apply with a wet medium. Do a quick image search for plaster crown molding or ceiling medallions to get an idea.

P+L is also significantly harder and denser than the drywall that replaced it. You end up with significantly less noise traveling room to room, and it is much hard to scratch or dent from an errant piece of furniture

Maintenance + Repair

There are a thousand and one tutorials on repairing cracks/holes/etc with P+L out there. I won’t rehash them, but I will emphasize understanding of the the original installation as crucial to proper ongoing repairs.

Almost all plaster and lath issues stem from the plaster surface becoming detached from the keys through the lath. This could be from physical trauma of a past remodel or alteration, or simply from the movement of the house over time. Water damage can also frequently cause separation of these components. With any issue where keys are broken or missing, the remedy is going to involve re-adhering the plaster to the lath. No matter how much “spackle” you put over that crack or loose section, until you re-adhere, it is going to return.

An easy way to test a plaster wall it to simply apply pressure to it, slowly, and see if the plaster flexes. This will often be accompanied with an acoustic component as the plaster interfaces with the lath where the keys used to be. Any project I have started a walked through on always incorporates this in every room. You don’t need to be scared of plaster and lath, you just have to know what you’re dealing with.

How Buildings Work

Knob and Tube

Anyone who has lived in a building more than 75 years old has run the risk* of utilizing an electrical delivery system known as Knob and Tube. There are anecdotes a plenty about the dangers of this system, and plenty of theories and opinions about what to do if you encounter it. To form your own opinion, let’s talk about it’s history, use and common problems. Of course, a good idea on what household electrical delivery is all about is probably a good background to have first and foremost.


If you walk down any typical street in a city and look up, you are familiar with K+T’s ancestry. Electrical power lines overhead apply the exact same principles as early in-home wiring, and these were derived from their predecessor, telegraph lines. The idea was simple: metal wires conduct electricity over distances rather well, and as long as they are separate from each other, were generally safe. This generally comes from the principle that power/telcom lines are far over head and won’t run into many unplanned obstacles.

When brought into the home, it was quickly apparent that these wires could not be left uncovered. With where technology was at the end of the 19th century, fabric covering was the easiest and cheapest option for manufacturing. So we now have insulated (with fabric, called loom) copper wires that are run separately due to their heritage. This same heritage brought with it half of the namesake; the knobs. These white posts keep the wire up and away from the surrounding structure. The other half of the name, tubes, came at the same time the insulation did. These porcelain elements allowed the wire to safely go through a structural element without direct contact.


Electrification started in the 1880s, with widespread use in most metro areas by 1900. Indoor lighting was provided earlier by the use of various flame powered lamps (candles, oil, gas, etc). The reliability of gas light in most urban centers resulted in many homes from 1890-1920 being installed with both gas and electric supplies to dual fixtures. For the majority of installations, K+T provided a modern lighting option, but not much else.

Knob and Tube was installed commonly until the 40s and 50s, when post-war manufacturing was able to reliably introduce metal and rubber coated wiring products. Unfortunately, this same manufacturing boom is what started introducing dozens of new electrical products for the home that knob and tube was never designed to handle.

Installation was performed by well trained technicians and required great skill in planning due to the dual wire nature, and all the supporting porcelain knobs and tubes. Additionally, any splicing or joining was expertly soldered and re-wrapped in friction tape.


So far, it’s hard to see how there could be any problems with K+T. The wires are all separate, connections are soldered, and they are only providing power to light fixtures. How bad can it be? Within those constraints K+T is incredibly safe. The only self-imposed danger is the degradation of the textile loom around the wire itself. Without physical contact from something else hitting the wire, however, even this has a relatively low danger.

Something Else. These two words are the reason for the perceived dangers of K+T. As the world moved forward, these old houses with K+T did not. We now bought things that ran on electricity. And when faced with a house that had ample electrical wire within it, just not the places where we wanted to plug things in, what decision did we make? Simply add on!

Remember when K+T yielded to post-war wiring? Remember when newer was better? Remember when all those new things were introduced? This is the trivalent problem of K+T. Not the wiring itself, but the fact that we have all these new shiny things to plug in, the only way of getting them power is using a different delivery system than what was original, and the mantra that both these new products and wiring systems were inherently better than what was there before. All of this coupled with a mentality of DIY that exploded post WWII.

So we no longer have soldered connections. We no longer have two separate wires. Knob and Tube never used junction boxes, so why would I now when I join these systems together? Combine these things with some knowledge around how electrical fires start, and you immediately see the danger of Knob and Tube. Modification and over-taxing of a perfectly well designed lighting electrical system is what you should fear, not K+T itself.

People are quick to point to Knob and Tube as the issue when looking to purchase an older home, one that is daunting to overcome. But focus on the modifications. If you can verify the K+T is in good condition as far as the fabric loom and no broken knobs or tubes, and can show good evidence there are no additions/modifications to that system – keep using it as-is. The safest things you can do are remove any possible changes, and update the current limiting device in the house. Electricians or contractors who say you must rip out the whole thing and start from scratch are just using scare tactics. (There are plenty of instances where your insurance may want K+T removed. Typically, though, they just want the over current device, most commonly circuit breakers, to be as up to date as possible)

So there is my rant about Knob and Tube. Love it. Admire it. But most of all, understand it, and understand where the real dangers are. Oh, and never, ever, add on to a knob and tube circuit 😉