KNX is a smart building system. If your mechanical or electrical engineer isn’t familiar with it or doesn’t feel they are up to it go to the vendor that told you about it in the first place. They will have persons, firms, and contractors that can handle this system.

Be aware that many groups that tell you about systems such as KNX have a financial incentive in specifying these systems. This is why I recommend going through an engineering firm. They will design it based upon the criteria you establish and building codes only. They have no interest in whether you want to buy their products.

Most unit prices consist of averaged prices across a class of project.

A typical example would a multi-family project.

A multi-family residential building from 3–5 stories will not change much per square foot either at 3 stories or 5 as far as estimates go. At 6 stories you will see a price jump as structural and fire requirements change at this point. The price will stay consistent until you breach 10 stories. This time it’s due to the change in equipment needed. 11 to 30 stories will again stay fairly consistent. At 31 stories you are dealing with a logistics nightmare. The deployment area is tiny and everything going in and out of this building needs to be timed so that the surrounding trees and buildings are not overwhelmed by your construction activities.

It should be noted that most projects over 15 stories require a precise estimate involving the final contractor as seemingly minor changes and variations can spiral costs out of range.

There are few things you need to remember about old, historic and/or period buildings and housing. You aren’t seeing the typical example from the time. You are seeing the best, most expensive, most well preserved examples. Most of the examples you’ve seen are the mega-mansions of their time.

The next thing is homes and buildings are reflections of their time. What is available to build with. What do people think is aesthetically pleasing. People like the current houses even if you think they should all be burned to the ground.

We can change any time, but cost and preference is currently driving us in different directions than medieval village.

Most of the other answers are rather entertaining while only touching on the truth.

The reason is fire and human safety.

Most long-lived cities that don’t have these spaces, called setbacks, have either burned down or were demolished to place setbacks.

Setbacks are areas around structures or properties used to stage fire fighting activities and as routes for building occupants to use to get away from endangered structures.

For the more observant, yes there are many examples where buildings come up to the edge of the property or a neighboring building. Typically one of two conditions is occurring here. First, the building is up against a location that is assumed to never possess a building, such as a street front. Second, and this may be required even if the first condition was met, the wall located along the edge must be constructed to a level where fire isn’t expected to destroy it, won’t collapse along with the rest of the building, and is heat resistant enough to hold off the heat of a raging fire for four hours (basically a fire on one set would need to burn for four hours before the transfer starts lighting paper on fire on the other side).

In modern construction this usually requires a solid concrete or masonry wall 8″ thick and extending 2′-4′ beyond any lesser construction with no openings, doors or windows. (There are alternatives, but I’m not going into those.)

History has taught us that without those setbacks, your city is going to burn down, likely with many of its occupants, at some time in the future.

In general, it won’t make much of a difference whether you use type O or N mortar in this case. Also, I would stay away from lime mixes unless you in fact know that was what was used before (its also amongst the weakest mortar types).

You are more interested in the components of your mortar than the strength rating (the type O or N in this case), unless your building is something other than house or more than three stories tall.

Limestone can be highly reactive to some components of cement and mortar. If your local hardware stone has mortar for limestone, you can go with that, but typical cements and mortars can change formulas depending on market values.

So, how do you tell?

Get a small sample of the mortar you plan to use. Mix it up and apply to an area of limestone, preferably to a number of stones. Let it dry. Check for any white or chalky material that may have formed on the mortar or around the edges, especially the bottom edges of the mortar. If this happens, you don’t want this mix. If it doesn’t happen, soak the mortar completely again and wait for it to dry. Do not help it to dry by applying heat or fans. Check it again once completely dry. If you still don’t see anything you should be out of danger, but you may want to give one more cycle.

Provided you didn’t get anything, the mortar will at least work for re-pointing. But, remember that you may still get white efflorescence over time. Limestone is very reactive, as I pointed out before. Should this happen (down the line and not during our test) use something like a wire brush. Do not use muriatic acid like they do for bricks. It can dissolve your stones.

I hope that helps.

Most skyscrapers are assumed to have a lifespan of about 150 years. Modern maintenance and construction methods have been extending that so that older examples getting near that number are proving to have considerably longer lifespans.

But in many of the cities you’ve mentioned skyscraper tend to get replaced every 50–70 years, especially when they are non-residential skyscrapers.

Lastly, Dubai is a very young city in regards to skyscrapers, so it may be the one to follow to see how these things are addressed in the future.

First off, everyone needs to understand that strong winds and tornado winds are in completely different classes.

Fortunately, there is a phenomenon called the heat island effect that tends to steer wind events such as tornados away from areas with skyscrapers. Basically, areas, where we build such structures, are also accompanied by large areas around them covered with concrete or asphalt. This creates areas of heat being released back into the air, much more than grass, dirt, or most normally encountered naturally occurring surfaces. In order for a wind event to move into this area, which is quite large and with skyscrapers more or less in the middle, the system has to expend more energy to move in that direction. As such, there needs to be a lot of factors working against you for a tornado to run into a skyscaper.

Skyscrapers are designed to withstand high winds far and away beyond the highest wind recorded in that area. There two areas of concern in the case of a tornado hitting a skyscraper. First, weak or brittle structures, such as glass, are likely to break apart from the shock. This opens the building up allowing for forces to be applied to the structure that were never intended by its designers. Second, the sheer magnitude of the wind can cause force-multiplying effects that were not considered as the likelihood of the situation was too remote.

Just as a side statement. It isn’t the goal of building designers to keep the building safe in all situations. The goal is to keep the structure sound enough to allow the occupants to escape.

Most skyscrapers have a large glass area allowable due to the structural frame tending to be internal. The problem here is that occupants that weren’t in a protected part of the structure, such as the stair or elevator cores, are not only subject to the full force of the tornado, but likely tunneling or vortexing action which would intensify the wind speed and pressure within the structure. This would be like a car crash occurring everywhere within the building. People, furniture, partition walls, anything except for the cores stand an excellent chance of being swept out of the building. Anyone in the cores would experience large pressure swings likely sufficient to buckle doors making the problem worse. A lot of these people would find themselves being thrown down at least one set of stairs to the next landing.

The frame of the building will likely do fine as it has a much smaller profile than the whole building so collapse is relatively unlikely.

The only saving grace in this scenario is that the tornado would move through the building quickly, about the speed of a car. Once past the wind force drops immediately back to high winds or less. So, if the initial blast hadn’t pulled you from the building it is unlikely to do so at this point. But, you’re still in the debris field except that you are no longer protected from it by the skin of the building, and there are many loose objects around you.

You would need to find cover as best as possible until the winds died down to a manageable level, which should be in the next few minutes. Now you’ll need to work on getting those stair doors open and getting down to street level.

Rejoice, kiss the ground, you just survived one of Earth’s little miracles.

Remember that once a tornado passes through an area you need to be very aware of your surroundings as many things have become unstable and dangerous.

This is a matter of visualizing the scenario and it pretty much explains itself.

Let’s start with two random shaped plates with jagged edges. Place them together so that they touch. Now place a finger on a random place on each plate, and push in a random direction generally towards the other plate.

Whichever parts touch first are going to have the greatest pressure. If that part breaks, crumbles, or gets pushed out of the way somehow you get an earthquake.

Now in real life, we don’t really know what the edges of these plates look like. And there are a lot of huge pieces of plate rubble between them. The plates are anywhere from 5 to 30 miles thick and of varying strength. The things we call fault lines are either the surface eruption or an approximation of the center between the two plates. the movement of each plate is fairly easy to determine, but meaningful edges are much harder. Also, the forces behind the movement slowly change over time just to through an additional wrinkle into the mix.

We have reason to believe that we will eventually be able to predict these things but we still have a long ways before we developed tools to get the information we need first.

For the most part, they aren’t. But, there are holdovers.

Basically, a large part of the banking system grew up during the “Old West” period where the US was expanding. All exchanges were physical money except for loans which were recorded.

So, bank buildings were designed like secure boxes. Better ones were built like cages. The best were built like vaults. As a result, few people robbed banks, but mostly robbed the runners shipping lots of money to various places.

In New York some of the best of these examples still stand, and Hollywood loves them. Giant stone buildings, guards, ornate gates and cages, visible security like cameras. Most of it meanless. This is all show to make customers feel like their money is protected.

Simple answer. It used to be for protection, but now people still like the feeling that their money is protected.

These are the lumber grades in the US:

General construction lumber:

Lowest

Utility (Not usually available to the public)

3 (Not usually available to the public)

2, Stud, or Standard (Lowest common grade)

2+ or “2 or better”

1 or Premium

1+ or “1 or better” (Highest common grade)

SS or Structural Select (Considered the highest grade, usually special ordered)

“Center, free of heart” is considered equal to Structural Select, but less likely to twist.

For veneer, layered, laminated wood, and finish woods:

Lowest

E (Has the largest filled knot cutouts)

D (Not a visual grade)

C (Common outer layers of structural plywood)

B (Paint grade veneer)

A (Varnish grade veneer)

For mechanically grade lumber:

M-## (The number is the tested strength of the lumber in given units)