Yes, but it’s going to get pretty thick if you don’t want cracks.

On most soil, you can get away with about 8″ thick. It will need to be nearly a perfect rectangle no length longer than about 100′and the short span must never get less than half the long length.

If you get outside of these proportions you need to increase the thickness rapidly. A longer slab will break up due to ground friction as it cures, so it needs to be thick enough to counter that. If any portion is narrower than others it needs to be thick enough to deal with that concentration of stresses.

You can end up with a three-foot thick slab on a seemingly normal-sized house fairly quickly.

Or, you use a 4″ slab with reinforcement that handles almost all typical situations with 6″ slabs handling virtually all reasonable heavy use situations.

Short answer: yes, but not a very good one.

Obsidian is very similar to common glass. This means that it has very high compressive values with very low tensal values. Hitting a “sword” against another object puts it in a state of bending (compressive and tensal forces at the same time) which means it will break with relatively little force. Hit it hard it is likely to fracture explosively (relatively speaking).

It would be heavy and difficult to construct.

Generally, I would recommend against it.

In that the nail plate (my office know them as gang plates) are everything because they are what hold the pieces of the truss together. Trusses that use nail plates rarely have any other fastener used in their construction.

This answer changes depending on how you define things.

If this is a strength issue; you need to design the new slab over the existing.

If this is a finish or a wear surface it can get very thin. Some epoxies can get down to a couple of micros thickness, but that may not fit your criteria. Grout can get down to 1/8″ or less, but needs a suitable backing. Also, it is very fragile. Fiber reinforced toppers go from 1/8″ for non-wear to 3/4″-1″ for wear surfaces. Lightweight and regular concrete toppers tend to be about 1.5″ and do contain wire mesh reinforcement.

So, back to the question, how thin can I pour concrete over existing? Depends on your criteria, but if you don’t know, go with 1.5″ lightweight with a wire mesh. Don’t forget that if this isn’t a ground slab that you’ll need someone to do an analysis to see if you can support the extra weight. Any concrete adds weight to structure at alarming rates.

Elements – the physicals parts.

Principals – the ideas.

Let’s get real simple.

Non-structual – pretty much only holds itself up.

Structural – used to hold itself and others as well. General considered to be important if not critical to supporting the structure.

Ian Marr·June 28, 2020Architect

I would explore openings or skylights. But, without an accurate description, everyone is just shooting in the dark. (Sorry for the pun.)18 viewsView Upvoters · Answer requested by Heather KendallUpvote3
Add CommentIan Marr·July 9, 2020

If I understand you correctly you should have about 7′ of clear space under your deck. Assuming you have 1–3 open sides of that under-space, that alone would provide significant natural light. With 7′ of clearance, you can expect as much as 7′-14′ of direct sunlight penetration depending on which open sides are open to which directions (South facing gets the most light, Est gets more morning light, West gets more evening light, and North gets less light but it tends to be more even.)

Unless this is a 50′ deep structure most shade tolerant lawns would grow under those conditions.Upvote·1ReplyHeather Kendall·July 18

ty for the thoughful answer!

This deck connects to an elevated solarium (so, probably about 15′ depth) and has a big hill with a forest on one side. Closest to the lower floor of the house it will have almost no light a goodly portion of the day because of these semi-unique features. Hoping that bringing some openings closer to where the deck meets the solarium will help it get enough to support shade tolerant lawn alts.UpvoteReplyHeather Kendall·July 9, 2020

ty 🙂
We just took the old deck apart or I’d get you shots.
What description factors would help?

It will be about 8′ up and attached to a solarium that is likewise elevated. (The old one has been attached to the same, but about 2-3′ lower, at different points)

The width/depth of the new one, which we’ll be re-purposing as much of the old deck material for as we can, are presently under consideration.

Once we get the deck raised and the space flatter, there will be significant yard space underneath that we’d like to have some lawn alternatives grow in and have it be pleasant for people to hang out in.

Understand that when dealing with wind, a 105mph rating and safety factor may not be quite what you think they are.

the forces created during 105 mph rated structure allow for gusts and sustained winds that exceed 105 mph for at least 60 seconds. That is literally what your factor of safety is for. In this case, the factor of safety would be between 1.5–2.5. That would you possible protection up to about 140mph in a 3 second gust and about 115–120mph in a 60 second sustained gust.

Keep in mind that for every 5 mph increase major problems start creeping into your scenario. You need to remember that this doesn’t reflect how well the structure is attached to the ground or if local terrain/ buildings are magnifying the wind.

That original number is where the engineers who designed it feel that a normal user, without special knowledge, can safely use the structure under conditions which may occur at those wind speeds.

Yes, but to a point.

First, let’s look past the idea that this is addressing just one problem and ignoring any others.

Okay, round geometry would reduce the wind loading on the structure, as long as it is a single continuous curve. Changes to that curve will quickly lose any benefit you gained.

But all you’ve done is reduce the required strength for wind loading. If this was the largest load of the building, great! If not, you haven’t done anything. Also, remember that we tend to build this out of straight lines so curving parts cost more.

Next the roof. During hurricanes, or any high winds, if you lose integrity of your roof you get a massive negative pressure inside your house, then your house probably disintegrates. So, if your roof isn’t up to the task your walls don’t matter.

The truth is that we can build things strong enough that shape really only comes into play in the following scenarios:

• The weight of the building and its contents affects the gravity loads. Shape is less important, but the size of the interior spaces is.
• For earthquakes, the more weight you have further from the ground, the harder it becomes to support the structure. Not shape, but the distribution of weight.
• Lastly, wind. Wind loading is all about surface area. Large flat vertical surfaces act like a sail. Large flat horizontal surfaces like trellises act like a kite. Small surfaces just don’t catch as much wind. So, here shape is important, but really only the surface area in any given direction.

The transport company maps out preferred path of travel.

This path is usually submitted to the state transportation authority along with city or county whose roads will also be used (multiple state departments if crossing state lines). Details of the trip, equipment used and support vehicles are described in the permit (The state will have general guidelines already laid out in their permitting literature, and is generally similar across state lines.)

The permit is reviewed, and a timeline is established between all jurisdictions. When the transport can operate, what roads will be used, what support vehicles, does it require a police escort… and lastly, are there any modifications to public property that is required to transport your object.

Back to your question. Local cities will establish a route that allows the transport to occur. They will also decide if your support crews and vehicles can direct traffic as needed or if local police will do this for you. If modifications to public property is needed it is likely that this is taken care on many months prior to your transport.

Things that are multi lanes wide tend be moved at or near 3am when traffic is the least, if possible.

Very large objects can take a year or more of planning and approvals, but most take about a month to setup.