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.

According to “The Skyscraper Center,” the US has the most buildings categorized as skyscrapers at 5,418 vs China’s 4,480.

But China beats everyone at categories from 150+ meters.

The top 10 in the skyscraper category are:

1. US – 5,418
2. China – 4,480
3. Brazil -1,513
4. Canada – 1,194
5. Australia – 1.134
6. Rusia – 840
7. Indonesia – 670
8. Japan – 647
9. UAE – 637
10. UK – 478

The top 10 in the 150+ meters are:

1. China – 2,177
2. US – 807
3. Japan – 257
4. UAE – 253
5. South Korea – 221
6. Canada – 111
7. Australia – 111
8. Thailand – 106
9. Indonesia – 105
10. Malaysia – 91

As mentioned below, it probably isn’t the beam that is doing the bouncing, but the floor joists.

Let’s assume straight off that you don’t want to replace the joists.

So, we are reinforcing the joists. You have three areas you can work from: the top, the bottom, and adding supports.

The top.

• You can double the nailing on the subfloor (provided that you aren’t increasing the nailing to less than a nail every inch). This will allow less flexing of the subfloor, but will only help a little.
• Add another layer of OSB or plywood on top of the subfloor with a similar nailing pattern to the existing subfloor (or replace the existing subfloor with thicker sheeting). This will stiffen the subfloor diaphragm which will reduce the bouncing the thicker you get. But, now you have a change in height of the floor.

The bottom.

• Much like above you can add 5/8″ drywall to the ceiling with screws at 3″ on center or so to reduce flexing. This will be about as effective as adding sheeting on top.
• You can expose the joists from below and add bridging between the joists every 4′ on center. Again, this will help a little.
• You can expose the joists and either sister joist or cap the joists. Sister joists are joists laid next to the existing joists for the full length of the span. Full height joists just need to be nailed in place, less than full height joists need to be nailed to the existing joist 6″ on center along the top and bottom of the sister. One per joist is best, but even one for every three or four joists will improve the bounce by a lot. Capping is like sister joists, but you nail it to the bottom of the joist like a 2×4 nailed on the bottom of a 2×12 like an upside down “T”. They should be nailed 6″ on center and every joist would need this. This will reduce the bounce by a lot.

Supports.

If you want to go with supports you really need an engineer because you can just as easily make things worse on this if you get it wrong.

Hopefully, this helped.