The typical loads are:

• Dead loads – the weight of the building itself (concrete, wood, metal, permanently attached equipment…)
• Live loads – the rated weight of everything to be placed in the building (people, furniture…)

In structural engineering there are other loads that need to be accounted for by code (per ASCE 7), if they do or could exist:

• Dead load
• Earthquake load
• Flood load
• Lateral earth/water pressure
• Live load
• Roof live load
• Rain load/ Ponding load
• Snow load
• Wind load

All of these are calculated in different weighted combinations.

And then there are special case loads for ice, waves, or explosives.

Well, driveways are made with cheap materials. The difference is how it is built.

Typically, you want 3″-4″ of concrete thickness in your driveway. 6″ if large trucks drive on it regularly.

If your driveway has rocks larger than a golf ball you’d want to add about the same thickness. But, rocks are okay as long as they don’t pose a driving hazard.

Pretty much anything as hard as a brick will do fine in a driveway.

Now back to the question.

Bad signs:

• Wood laid in the concrete as elements.
• Cracks. Most cracks are quality control issues unless you can stick a twig into one. Then things are moving either due to soil conditions are something like a nearby tree.
• If you have cracks and can see that the concrete thickness is 2″ thick or less.

Romans use what is called saltwater cement and we use portland cement. Both are the binder for concrete.

We can tell by analysis of roman concrete what the composition is but there is debate about the formula used. This is likely because like modern cement there is a large number of combinations and proportions that result in cement. Two things we know very well, they used a lot of pozzlin and they cured the mixture in forms in saltwater.

The romans pretty much used concrete to form bricks of concrete. Bricks of all sizes. The saltwater curing process required submerging the concrete in the saltwater so forms were needed, hence the bricks.

As far as quality and strength we really only see the most durable examples so what remains may be less typical than it seems. Also, it has had a long time for any residual curing to occur.

Modern portland cement and thereby modern concrete doesn’t need emersion in water much less saltwater. We just mix it in and pour it into any forms we’ve setup. As such, modern concrete is more versatile than what the Romans had. Also, we use reinforcement, which the Romans didn’t use, to over come the weak relative tensile strength of concrete so that we can make much more slender constructions.

Firstly, there are different types of both aluminum roofing and shingles.

Aluminum shingles – some people like the look, many don’t. They are fairly fragile to impact but otherwise can last 10–15 years. Inexpensive. Aluminum requires precautions when touching other metals.

Aluminum sheet or standing seam roofing – very distinctive look. Considered one of the best sloped roof types for longevity. Expensive.

Wood shingles – Inexpensive and durable. It is combustible which has restricted its use in many areas.

Asphaltic or composition shingles – Inexpensive and very durable. Generally considered to be one of the best roofs, but is also considered to be less attractive than other options.

Okay, there are several things at play here.

Screws are a mechanical fastener that cuts into the wood and holds because you’d need to either pull the plug of wood out also or pull hard enough for things to sufficiently deform for the screw to slip past. Now, in each case the screw will likely break before either occurs.

Glue does have mechanical properties once hardened (for the same reasons as above), but it is primarily known for its chemical bonds. Due to the nature of the materials involved wood glue, which will penetrate into the wood itself to a small degree, owes most of its strength to the mechanical bond (at least in this conversation).

So, if you just coat a screw with glue and screw the fastener in… You’ll pretty much have exactly the same values as the screw by itself.

If there is an existing hole/void that your putting the screw into the glue will aid as a filler. Its worth noting that most wood glues shrink as they dry so the interface between screw-glue and glue-wood is likely to be partial at best. But, if we assume that the whole void has been filled by screw and glue… You should have nearly the same value as the screw, but probably a little less. And that’s your best case scenario.

Basically, the glue would just act as a wood filler.

On the surface that sounds reasonable, but the answer requires more.

As several others have mentioned cinder blocks are different from CMU (concrete masonry units) but still the price is similar. A block may cost about $1.00 ea while wood studs are $2–3 ea. You need one stud every 16″ plus bottom plate, double top plate plus sheathing, let’s call it $30 per 16″ section. Block takes 12 blocks to get to the same height so $12 per 16″ section.

Block wins let’s all go home. But, wait!

Studs require nails, screws, and hardware. Block walls require rebar, anchor hardware, and grout. And studs require less than half the labor that block does. Also, block buildings require much sturdier floors and roofs as block walls can exert much greater forces on those elements.

In general, wood framed structures tend to be the easiest and cheapest to construct. We usually only consider things like block construction when there is an increased concern about fire and egress.

Typically, a structure that is constructed out of block and is cheaper than wood frame is a dangerously under constructed structure.

Historically there have been a number of factors limiting wood framed high rises.

First, has been combustibility. With such large populations that have to pass through such narrow areas such as elevator and stair cores an increase of possible fire made such designs unfeasible. North America and Europe had hard caps on wood framed buildings at about 5 stories or 60 feet in height. Since that time we’ve developed several strategies to combat this. Better controlled egress, better fire resistant wood framed construction, and lastly wood framed systems that can maintain their structural properties even during a fire. The most resistive element to building height has been combustibility. Once that threat is eliminated is falls to other factors.

Second, wood sources have been yielding weaker and weaker wood materials. Over time we’ve come up with solutions. By combining layers or chips or wood fiber with resins and adhesives we’ve come up with scalable wood products of great strength compared to “natural” wood members. Additionally, since these can be “layered up” they can be produced at any size at any length. Suddenly, you can produce a beam or column several feet wide by several feet thick that is over a hundred feet long. We’ve never been able to do that before.

Once you have those two items addressed you now have a material that can compete with steel and concrete. And yes, we are starting to build high rises out of wood now.

You’ll get a lot of simple single point answers on this, but there are a lot of reasons for and against.

Let’s start with a simple pro and con list:

Pros

• Pretty or at least attractive to most people
• Decreases thermal gains in the structure
• Increases the insulation on the largest surface area of most structures
• Increases the thermal mass of the building
• Decreases solar island effects
• Increases vegetation in the area

Cons

• More expensive than most roof systems
• More complex to setup and maintain
• Much heavier requiring additional structural support
• Requires constant maintenance
• Requires an irrigation system
• Can easily trap water against your roof/structure increasing the likelihood of leaks
• Growing organics can undermine and penetrate waterproofing structures causing leaks
• Can freeze or delay water runoff, increasing the weight of the roof

So basically, you do have an aesthetic, but you’ve more weight and water issues vs better thermal qualities. Most of these number will vary so much based upon the specific structure that an analysis would need to be done each time rather than a general value.

But, there is one issue that will kill it for most designers. Maintenance. Every homeowner swears to the heavens above that they will maintain the garden roof. They never do. Take a look at any sod or landscaped roof you can find. Maintenance issues. They blame the designer, the contractor, the landscaper, but they almost never do anything to maintain the roof other than watering it. Until that breaks too. It is a large commitment to have a sod or landscaped roof. Sure they were great in the medieval era where if it got a little damp they increase the fire inside to dry everything out. This doesn’t work with modern finishes and electrical systems. Imagine what would happen to your TV if it got “a little damp”.

So, there you go. A great idea from another era that only works today at great expense and/or effort.

Firstly, ferrock is concrete, just with a different aggregate make-up. It is applied like concrete, transported like concrete; it is concrete.

So, ferrock is concrete with a sizable content of waste iron and silica. The strength varies greatly depending on the proportions used, but, generally, it comes in at 5,000psi – 7,000psi at 7 days. This makes it equivalent to medium to high strength concrete. The likely ferrous content is believed to consume most of the CO2 produced by the cement.

In theory, it should be cheaper as you are dealing with waste products. But, if you want it at any scale then it comes from a concrete plant. Now the cost is wholly dependent on what it takes for them to get it for you. And even waste iron is likely to cost more than crushed rock.

Most designers, architects, and engineers tend to use it for ground applications. This is because it isn’t well established what problems it does have.

• It rusts. Specifically, it grows rust crystals as it is exposed to water. But, some examples don’t seem to. So, this will depend on the iron content and form in the mix.
• It can stain nearby materials. Again, this depends on the amount of iron and in what form it comes in.
• Efflorescence. It’s concrete so any salts that are in the mixture or form in the mixture will tend to leech out in the presence of water.
• Rebar. It isn’t clear how reactive to the rebar it is, so does the rebar need to be coated?
• Water. There are a lot of materials in this product that react in the presence of water.

This is a niche material using a waste product for aggregate. This means the chemicals present may not be known and may react with their environment. Using it for pavers or durable surfaces is probably fine but for a concrete replacement it has a long way to go. They need to be able to accurately predict the chemical processes that will result. A number of producers have gone to great lengths to solving many of these issues, but still, they haven’t been able to placate the fears of iron-water reactions. As such, most potential users of this material view it as another novelty brewed up by desert eco hermits. It may be great, but are you willing to test it?

This question contains two parts going in different directions.

The typical answer (the one supplied by most building codes) is 1/4″ per foot for drainage. The actual minimum slope for drainage is closer to 1/64″ per foot. At that slope gravity stops becoming the driving force behind water. Air movement, surface tension, and capillary flows start dominating water movement.

At what point does concrete become a slip hazard? This varies a great deal. Again, if we go by values supplied by code it gets placed at 6% slope (6′ per 100′). Actually, a lot of codes use roughly this slope to warn about a number of conditions.

Basically, water drainage we predict, slipperiness is dependent on specific conditions of you walking on the concrete.