This is from the $50 Underground Home which is post and beam and has the same back patio as well. The guy who wrote that book lives in Northern Idaho. Now Bounter County is starting the building code enforcement harassment. Which means they have the Globalist Agenda's going on. They don't let you build these homes and the author of that book was made to move out of that home. It's still there but more as a museum type building to show how viable it is to live in these cheap structures. Your Wofati is a much more spacious looking structure than his but it works being underground.
I have a idea. You can take curragated plastic which is double walled and weld 4' x 8' sheets of it together with a heat gun or even parchment paper and a iron will weld it together. You could use it around the posts and under the floor and on the outside of the walls. You could use it completely waterproof the underground building including the posts and even rap it up and over the roof beams and shething to make it moisture damage proof. You can salvage those 4' x 8' curragated plastic from election signs. I got 8 of them from the 2020 election. If you buy them in bulk you can probably get them for pretty cheap if you want them brand new. You got people making foldable boats and kayaks out of these. They even show you how to weld them together. If you completely inclose the underground home including the posts and make it water tight and cover the plastic with dirt. The sun can't deteriorate the plastic. Your building is going to last as long as the plastic does. They say these plastics take 500 years to deteriorate. Have air circulation on the inside come from large tubes or plastic pipes from the back also welded to the curragated lining like they do in earthship homes. And like the earthship homes you have at least one wall not covered in dirt. With windows and etc. Who needs it facing the south. You can grow food on the back patio area and use mirrors to get light to those windows. That's what the author of the $50 Underground home did. One thing I would do is make the post and beam roof super solid, strong probably using a thick layer of hempcrete at least 8" thick then a hemp-mortar about at least 2" thick over that then put about 3.5' of river rock then sand then soil. Have the roof gently sloop for water catchment and drainage. Why Hempcrete? It fossilizes with time becoming solid hard rock. You would have about 10" thick layer of stone over it and if you incasedbthe whole house in that then used the curragated plastic wrap? That house would last forever the wood would never get wet and rot. Think about it? The most energy efficient home that can last for at least thousands of years incased in solid fossilized rock? It could withstand any weather conditions including flooding because it can be built high on a slope or into the side of a steep hill or mountain? It can handle any climate.
