My Viva Vivas seastead design

(Chad Elwartowski) #1

Just figured I’d create a thread here for my seastead design in order to hash things out and answer any questions. (pictures in the next post)

(Live that you may live)

An affordable, configurable seastead design for the masses

The key to this design is taking the most basic building block, the triangle, to build a highly configurable, and scalable solution to meet the needs of any individual from rich to poor, single to large family.

Steel and Polyurea

Before getting into the design I will address the materials that would provide the best results. The main component is steel. Steel has been used for ship building for over 100 years, it is proven, it has a high carrying capacity and a high strength. It can take constant repeated banging against other structures without degrading over time like concrete. Its major downfall in the ocean is the corrosion and rusting due to salt water. While most ship owners address this with paint every few years, there is a better product that is perfect for seasteading.

Polyurea is a type of elastomer, most commonly known for their use in bed-liners for pickup trucks. It was used to coat the Boston tunnel, it is used in many underground bunkers to keep out water and it is being used to coat the US Marine Corps Amphibious Assault Vehicles (AAVs) which is being extended through 2035. They use it because it prevents salt water corrosion on their armor and if it takes a bullet, the polyurea will help stop it while being able to form back to its previous shape. Polyurea is being used more often, many people will coat their garage floor with it, it is being used to coat rooftops and many ships use it on their decks so they do not have to continue painting, Coca Cola refurbished one of their water tanks by sand blasting the rust to a shine and coating the steel with polyurea. The price has come down and the materials can be purchased for prices similar to marine paint.

Small Unit

The smallest unit is a dorm room sized floating structure 21.7 sqm which can be combined with more units to provide more living space as needed. The height and width of the small triangle unit is 5 meters. With these measurements a small unit could have its two floors split at 2.5 meter heights and put on the back of a trailer without the need for an oversize load permit so manufacturing could start inland with the units shipped to a dock where they are assembled and floated out to the rest of the platform. The light weight of steel vs concrete also means that manufacturing can be done on the seastead itself with a constant supply of steel plates.

The total surface area which would require steel plates is 107.5 sqm.

A 1m x 1m x 14mm stainless steel plate weighs 238 lbs. 107.5 sqm at 238 lbs per sqm is 12.8 tons. A quick search on Alibaba shows stainless steel plates can be purchased for around $500 per metric ton. At $500/ton the smallest unit only requires $6,400 worth of building material for its shell. Shipping and manufacturing costs would drive the price up but over time could come down with bulk purchasing and streamlined production.

While it will require more cost for a glass ceiling, solar, electric, plumbing and everything else that a small unit would require, it still leaves the price of the smallest unit at a reasonable cost for even a small investment.

Large Unit

A larger version includes a sphere which provides the largest square footage per surface area and is the strongest shape against any possible waves. Each sphere is 10 meters in diameter providing different configurations for different square footage.

Each sphere can easily provide 3 floors at least 2.5 meters tall with either high ceilings at the top floor or more space while at the bottom floor there could either be another small floor or a large storage area or viewing area if the configuration has the bottom in the water. For each configuration the sphere provides 235 sqm of living space plus any other space gained from the triangle unit.

Four different configurations can be set up, the sphere in the center with the top being in the open air and the bottom being in the water. The sphere on top with the sphere resting inside the large triangle unit with the top half way out of the shell. The sphere on the bottom allowing for the full triangle surface to be used for anything while half of the sphere sits under the water. And a split sphere setup where half the sphere is on top and half is below the triangle unit.

The split sphere setup allows for the most space utilizing the triangle unit for living or commercial space while still providing the same amount of living space within the sphere.

For a split configuration there is 570 sqm (6150 sqft) of living/commercial space. The total surface area is 2269 sqm required for the steel material. Using our previous calculation of weight and cost the material cost of the split configuration of the large unit would be $135,000.


These same spheres can be used as floating breakwaters around the seastead. With their large surface area and resistant shape they are able to dissipate the most water of any shape. With a high supply and manufacturing line used to build the sphere housing and the breakwater the price could be cut down significantly over time, with most of the labor costs staying on the seastead as the steel structures can easily be built from the seastead. The surface area for the sphere itself is 314 sqm. Using the previous calculations for steel cost that would put each sphere’s material cost at $18,700. For a 100 m diameter platform area the material cost would be $587,180 to have breakwaters completely blocking the inner circle.

Small, modular designs
What happened to the scaleable seasteads idea?
Marinea Oceanic Lifestyle | oceanic business alliance
(Chad Elwartowski) #2

Here are the images. I am not much of a graphic artist so these were the best I could put together with my limited graphics experience.

Smallest Unit

Cross section:

Sample Layout:

Sample Bedroom configuration:

Sample Living Room:

Combining two small units:

Combined living room/kitchen:

Small unit glass ceiling (should be made of a material that can be walked on or something light can drive on):

70 Watt solar panels:

54 70 Watt solar panel configuration:

36 small units attached to each other:

Combined to a hexagon shape:

Combined hexagon with 40 meter wide configuration = 384 units:

Large Unit

Large Unit center sphere configuration. 225 sqm inside sphere (excludes bottom portion and triangle area)

Large Unit top sphere configuration:

Large Unit bottom sphere configuration:

Large Unit split sphere configuration (570 sqm/6150 sqft):

Large Unit center sphere configuration:

Large Unit top sphere configuration:

Large Unit bottom sphere configuration:

Large Unit split sphere configuration:

Large Unit hexagon platform configuration:

Large Unit, multiple platforms attached:


Ring of breakwaters:

Breakwaters protecting platforms:

Combination of different platform configurations:

Grouped islands instead of one huge seastead?

I like it. The living spaces are compact and practical. You’ve got a good solution for power and light in each unit. And a good overall vision of how it fits together.

You’ve got some costs. I know that was Jason’s argument that CGI without a cost estimate is pointless. I definitely agree. I think our forum posts increase relevance when we focus on facts and figures. We can all discuss whether 14mm is sufficient or overbuilding, but at least it’s there to start with.



Ouch. I just got home from buying common steel plate for equivalent of $920usd/ton. Of course, they got it from an importer (apparently from Turkey), sheared it to my specs, and put it on my trailer for me. Yes, the lil trailer i built on the boat deck a few months ago. This steel is for the floaties under the deck.

Question for you, Elwar : why build with stainless and then Polyurea it? Stainless is still a pain to build with, if you are going to poly cover it anyhow, why not use common steel at half the price?

(.) #5

Lots of work and

(.) #6

I had similar ideas. Mine is a sphare with a hexagon around the equator.
The hexagons are horisontal and can link with eachother.
The linked hexagons can be circular and enclose a breakwater area.
The whole structure can be ballasted down, so only the dome part of the spheres
are above water. This would create a shallow water area.
The domes could be staggered in multiple lines for breakwater.

The triangles kight be better. Your presentation is nice, mine is none.


(Chad Elwartowski) #7

I’m far from a steel expert, I guess I figured redundancy. Can stainless steel be welded together or is it mainly good for fastening together? Most of the stainless steel on Alibaba is closer to $1k/ton but I saw a few that were $500. Yours for $920/ton is still good with shipping, shearing, low volume.

The cost I put on there is more of a base cost of the money leaving the seastead ecosystem for each unit. With people working on the seastead to put them together they would be paid and the price per unit would go up for the final buyer based on labor costs and extras but at least it gives an idea of the costs.

(Chad Elwartowski) #8

My last picture has one sphere for a hexagon just to give an idea of what could be done. The shallow water thing would be cool.

Using the domes for breakwater are good but I wouldn’t want to be the guy living in one of the front domes being pounded by waves all day.

I considered that the spheres used for breakwater could be used for something else but it’s difficult knowing they’ll be getting pounded. One thing I can think of is having the outside covered with Electroactive Polymers covered by polyurea so that the waves hitting it actually produce electricity.


It’s as different from common steel as aluminum is. It’s tougher than common steel, which makes it hard on tools to cut it. Just like you use different tools on aluminum, you use different tools on stainless. It comes in different alloys, not all resist rusting in salt water, and fastening the same alloys together with nuts and bolts can cause problems if they must ever be undone, i have had to cut the bolts off with an abrasive zip disc. Stainless tends to be brittle (ymmv) so it’s fatigue durability is less. It also can work-harden something fierce, so cutting tools must be sharp. Yes, you can weld it, but you may get a weld bead prone to corrosion and more brittleness. It cannot be cut with oxy-propane or oxy-acetylene torches.

There is a stainless steel (unknown alloy) ship sunk off Miami, maybe someone can go get some pics of it.

(Chad Elwartowski) #10

Thanks for the info. Are most steel boats made out of common steel?

(.) #11

Yes, I see it , the hexagon. That is why I think the triangles are better because they can be
formed into a hexagon. But the hexagon cannot be split into tiangles.
And the hexagon fits together with the triangles.


Correct. Even then, there’s different grades, requiring slightly different handling at the far ends of the spectrum. For the real cheap stuff (30k psi), you use more of it if you must use it at all, and for the pricey and picky stuff (HY-120 and up), you simply don’t use it. The 30k psi is used for rebar, the HY-120 and up for submarines (and some heavy truck frames). Everything i buy is 50k - 70k psi, the range where it’s so easy to get, make, and afford to just use two if you really need more than 10 tons per square inch of strength.

PS: the HY-80 and up is also used in those tall skinny construction cranes, like:

(Larry G) #13

Agreed. Getting facts and figures is what advances the cause. Good job on explaining the design and your choices.

One quick comment, that also clears up some of the stainless steel vs other alloys: Start with your design requirements made explicit. For example:

Structural material must resist corrosion in seawater without specific coating
Structural material must resist corrosion through a combination of innate corrosion resistant and anti-corrosion coating.
Structural material must resist corrosion through periodic coating with anti-corrosion materials.

(Chad Elwartowski) #14

I’ve always started on the premise that we need something that can stand up to salt water over the long term. That’s why so much discussion has been based around concrete as it has proven itself to be able to last.
While searching for an alternative I discovered polyurea. While studying polyurea I found that it works the best with steel (I have seen it on concrete, it does not do very well).
That’s the reason behind my decision to go with steel. As for which kind of steel, Kat provided some great input. The reason I chose 14mm was from a boat design forum where they were discussing the thickness of a steel hull in one of their fishing boats so I figured it was a decent thickness.

(.) #15

Where are you planning to build it?
Where are you planning to anchor it?


Well, it’s 1.4cm , or 0.55 inches. That’s pretty heavy, but it works if your goal is to minimise hull framing while battling the waves. Usa Gato class subs, and early German subs were 1/2 inch common steel, and rated for 300ft depths (later subs used stronger steel). The commercially made aluminum pontoons i have are .050 inches, the 14ft alum boat is even thinner. The steel pontoons i made were also .050 inch.

I hope to minimise material use by reducing the forces the seastead sees. For instance, a 10ft spar with a house on it is going to see a lot of stress from the house and waves, and will need to be very thick. Or you could put spars under the loads as needed, making them thinner so they are less of a target for waves, etc etc etc…

(Wilfried Ellmer) #17

@KatOnTri, this is a nice steel piece with a high degree on forming difficulty - you seem to be a “skilled steel crafts woman”. I would offer you a job on any of my ship repair projects…

14mm is a typical plate thickness for a 250m merchant ship …i have repaired tankers with only 8mm … the strenght is not in the plate thickness but in the underlaying honycomb structure. In modern marine engineering the outer plating is performing more as a “skin over a skeleton” than a structural element. The “roughness and crash worthiness” is rather achieved by double wall sistems than by thickness of the outer skin…

typical cost of a repair project of the size below USD 15.000 - typical service lifespan of those structures 15 years - so not the kind of structures for the phase 1 key converstation with a claim to solve the bottleneck

Afloat ship repair one of the business fields of a local floating marine cluster - development that will lead us to seasteading…


If that is so, then why must each seastead hull last 50 years or more? Whenever the sport fishing divers see a hull needs attention, change out that hull, bring it over to drydock, and repair it. I am not sure if Elwar’s design can or does use detachable floatation units, or if the design can fit on a floating drydock, so i deleted two paragraphs about drydocks that were prolly off-topic.

(stephen russell) #19

Love this, EZ to produce & ship out & build our sea city states, awesome
Have plants in CA CT VA FL NC ME to build modules
Jobs for all
Test city site: Hawaii, or off Cabo, Baja Mexico

(Wilfried Ellmer) #20

…certainly a possible approach - as long as the development is smaller then city size. At a certain size cost of maintainance becomes overwhelming for a condo development budget…