I am looking to build wofati/psp type structure this summer and have read through the majority of the threads in this forum. I would like to start up this thread to consolidate all of the lessons learned from the builds thus far into one place. Lots of ideas were discussed prior to building the wofatis and lots of pictures have been posted of the wofati construction, but much of the proposed ideas have not been talked about since construction and some key information is scattered between many threads. Let's see if we can't answer some questions here and make this an essential thread to read before starting a wofati build.
First I would like to discuss the difference in the construction of the roof of the two wofatis.
In wofati 0.7 there are girders set on the posts running front to back, then beams set on the girders running side to side, and on those was set the "decking" logs which will hold the plastic/dirt.
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In wofati 0.8 the girders are placed on the posts running side to side and the beams are completely left out of the construction. The "decking" logs are placed directly on the girders running front to back to enclose the space.
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Can anyone comment on why the method was changed between builds? The 0.7 version seems more structurally sound with the extra row of beams. The front overhang also seems more solid with the girders protruding out to carry the load, where 0.8 has only the decking logs extending out as the overhang.
Next I would like to talk on the front edge of the roof. Pual brings up his concerns in this thread about what to do with the plastic at the front edge. He also talks about the layers of dirt/plastic/newspaper at the edge on this thread. So I am wondering what the outcome was when deciding what to do about this hard edge? How is the plastic wrapped to keep water out? Does the dirt layer taper down to be thinner at this edge? Does water get in contact with plastic here and flow along the plastic under the dirt? I think this is a critical part to get right when building. Here is a picture of the completed 0.7, but it is not clear as to what happened with the plastic at the edge.
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Next I would like to talk about the different layers of materials used in the covering of the roof. Paul talks about layers of plastic, newspaper, dirt, and sawdust in this thread. From the construction pictures of 0.7 it seems like there was a layer of plastic placed directly over the logs, with a layer of dirt over that, then sawdust, another layer of plastic, and finally more dirt. Was newspaper ever used? How many layers of plastic were put down on the initial layer to prevent puncturing from stones/logs? How thick is the first and second layers of dirt? How thick is the layer of sawdust? Is there only one layer of sawdust?
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Next is the cob fill that was used between some logs. In Kristie's weekly pics thread there is mention of cobbing between the logs on the construction of 0.8. Here are a couple pictures.
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Was this cob used to cover all cracks between logs or just some? If some, which ones and why not others? Was there an issue with 0.7 that prompted the cobbing of the cracks? I see in this picture that some cobbing up of cracks was done from the inside of the exterior walls of 0.7 before the second winter to cut down on the draft. Thoughts on the draftiness due to the spacing between the logs? Should all wall and ceiling cracks be filled with cob?
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Next is the heat that escapes through the front, exterior exposed wall and where the wall meets the ground. It is discussed in this thread.
Here is a picture.
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Was this issue addressed in 0.8? Paul talked about putting in a straw bale wall in front like this. Is this still being considered or what about insulating below ground to the frost line along the front wall?
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I see from this picture that the front wall of 0.7 was insulated. How much insulation was used? Was the entire wall (except the windows of course) insulated?
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Next; what was done to keep the buried post ends from rotting? Paul talked about a mix of borax and DE to deter microbes. Was this done, if so how was it applied? Was any gravel/stones put in the hole before setting the posts or are they sitting on dirt?
This is what I could think of right now for points of clarification and discussion. Any talk on these or other issues to consider would be excellent.
First I would like to discuss the difference in the construction of the roof of the two wofatis.
In wofati 0.7 there are girders set on the posts running front to back, then beams set on the girders running side to side, and on those was set the "decking" logs which will hold the plastic/dirt.
In wofati 0.8 the girders are placed on the posts running side to side and the beams are completely left out of the construction. The "decking" logs are placed directly on the girders running front to back to enclose the space.
Can anyone comment on why the method was changed between builds? The 0.7 version seems more structurally sound with the extra row of beams. The front overhang also seems more solid with the girders protruding out to carry the load, where 0.8 has only the decking logs extending out as the overhang.
Next I would like to talk on the front edge of the roof. Pual brings up his concerns in this thread about what to do with the plastic at the front edge. He also talks about the layers of dirt/plastic/newspaper at the edge on this thread. So I am wondering what the outcome was when deciding what to do about this hard edge? How is the plastic wrapped to keep water out? Does the dirt layer taper down to be thinner at this edge? Does water get in contact with plastic here and flow along the plastic under the dirt? I think this is a critical part to get right when building. Here is a picture of the completed 0.7, but it is not clear as to what happened with the plastic at the edge.
Next I would like to talk about the different layers of materials used in the covering of the roof. Paul talks about layers of plastic, newspaper, dirt, and sawdust in this thread. From the construction pictures of 0.7 it seems like there was a layer of plastic placed directly over the logs, with a layer of dirt over that, then sawdust, another layer of plastic, and finally more dirt. Was newspaper ever used? How many layers of plastic were put down on the initial layer to prevent puncturing from stones/logs? How thick is the first and second layers of dirt? How thick is the layer of sawdust? Is there only one layer of sawdust?
Next is the cob fill that was used between some logs. In Kristie's weekly pics thread there is mention of cobbing between the logs on the construction of 0.8. Here are a couple pictures.
Was this cob used to cover all cracks between logs or just some? If some, which ones and why not others? Was there an issue with 0.7 that prompted the cobbing of the cracks? I see in this picture that some cobbing up of cracks was done from the inside of the exterior walls of 0.7 before the second winter to cut down on the draft. Thoughts on the draftiness due to the spacing between the logs? Should all wall and ceiling cracks be filled with cob?
Next is the heat that escapes through the front, exterior exposed wall and where the wall meets the ground. It is discussed in this thread.
Here is a picture.
Was this issue addressed in 0.8? Paul talked about putting in a straw bale wall in front like this. Is this still being considered or what about insulating below ground to the frost line along the front wall?
I see from this picture that the front wall of 0.7 was insulated. How much insulation was used? Was the entire wall (except the windows of course) insulated?
Next; what was done to keep the buried post ends from rotting? Paul talked about a mix of borax and DE to deter microbes. Was this done, if so how was it applied? Was any gravel/stones put in the hole before setting the posts or are they sitting on dirt?
This is what I could think of right now for points of clarification and discussion. Any talk on these or other issues to consider would be excellent.