Increased insulation Cob

I'm doing it now but the design is different from what I intend and also I think it would be better, if possible, to attach the horizontal wood on the wall in a different way because I think we don't have the right tools to make holes in the vertical timber. Is it possible to use L shaped metal junctions? Or maybe just some big screws....

Hey guys!

Finally I know what windows I have available! I have 6 1,64m x 1.23m double glass windows. As I said before, I decided to use slip straw method to build the walls but I'm encountering a problem. Actually, every time I decide which technique to use the same problem rises - it needs to breath. I think I'm failing to understand how can a wall be sturdy enough to face wind, rain and snow and, at the same time, be able to breath. If it's going to breath, then it's going to be permeable. If it's permeable, then it can't withstand such weather conditions and should be protected but, if I cover it, it won't breath!

I'm having a break-down, I really don't know what to do. I could just build away and forget about all these theories that I've been reading on the web but I suppose it's not very smart to make mistakes that can easily be avoided with some careful planing.

The design is now more simple. I didn't include the over-hang in this version but I have it in mind.

So, please, someone, any ideas on how to do this?

Hi Bruno,

I have been following along, and checking out the drawing, (ok design, but flesh it out more to scale.) Think of cobb this way if the wall is structural to it's self and the roof the cob needs to be thick and well laid. If you build a timber frame, for example, it is an infill and/or over laid method and can be thinner or as thick as you need for the climate you are building in. All cobb breaths, be it 100 mm or 1000 mm. If just does it slower. Use only natural plasters, and coverings and you will be fine. Hope that helps.

jay

Jay I decided to use slip straw. I sent an e-mail to Michael G. Smith and told me that in order to protect the straw from bad weather, I can plaster with lime or put some wood covering it but leave some space for air to flow. I think I'm going to do both.

Now I have a problem with the roof. I was thinking about building it using the same technique - slip straw - but I don't know if some horizontal ledgers will be able to keep the straw from falling off. Also, I don't know I can protect the upside of the roof from rain and snow...

I draw it up to scale and included some lines to signal where I'm thinking to put the vertical wood poles. Also, I added an extra "roof layer", just a sketch of what I can do to protect the slip straw roof

Hello Bruno,

O.k. things are speeding up here because of spring, so I have to be brief with projects on helping folks on.

The structure is more cave like that green house, there really needs to be more glazing-fenestration than earth walls, to be a green house or cold frame for raising plants, this is just to dark to be effective as it is now.

Your CAD of the building is helpful in seeing your ideas, now flesh it out some, put in beams, etc. (if you can't, I will try when I get some time.)

How thick are the wall going to be?

How are the walls built, just cobb, or is the form work permanent?

What is the form work made of, what size board and/or timber?

Cobb roof I think may be beyond the scope of your current skill sets. This building is rapidly getting to a point that you may need a secondary timber structure to make it strong enough, especially the roof. I can't tell because I don't know how thick you plane on that being?

Is this to exact scale?

What are you window dimensions, and how many do you have of them?

Regards.

jay

Plants are one of the three living organisms in the greenhouse. I'm more concerned with temperature so I'm willing to loose some light in exchange for better insulation.

I've made another draft, this time only with the wood frames. There will be no cob on the wall or roof. The walls will be made like they did here: http://www.youtube.com/watch?v=iSApSrd8VwY

For the roof, I want to use the same technique. As I was doing the new draft, I understood that it's better to make the roof without sloop. I'll build something on top of the roof to act as a "second roof". Something light just to protect from rain and snow.

The walls are 30cm thick. The draft is made to scale so you can just go and see the dimensions. The wood boards I used are 3cm thick but they can be thicker or thinner.

The windows are 1,63m per 1,23m and I have 6 of them. I drew them on the draft, also to scale.

The roof will be very heavy I need to add some support so I drew some lines going out of the windows to the ground. These lines can either be wood or steel.

In my head it will work fine but I might be wrong...

Well Bruno, it looks like you have gotten better at Sketchup, that is really good. As long a s you use light cobb (slip straw) you should be good, till you get to that roof. Flatter is going to be harder, because of the transfer of loads. You are going to need some pretty big timbers to hold that up. 300 mm thick walls should be find for the thermal mass/R factor. When can you complete the design with all components shown? What are you covering the walls with, and the roof. The roof pitch has to change to much steeper and/or heavy timbers to support the weight.

I'm starting to be a perfectionist with sketchup and now I'm doing the model again but the right way - components and aligned edges and all!

Tomorrow I'm going to visit a guy who can help with the the windows frame so I'll get an idea of how it's going to be and I can do another adjustment to the project.

Ok, I have an update on the sketch. Take a look and let me now any ideas suggestions

The final GH is the one on the left (near the origin). Everything is drawn to scale. Of course, anyone can use this sketch, it's completely free (this is me thinking that I've done something that can be of any use to somebody :p)

Questions-Concerns

Roof still might be to heavy to span that distance even if you use a "clay straw" infill, without employing some form of heavier timber work.

Is that the size glass you are going to be able to get?

Small spaces fill up fast, do you have the items that you plan to put in the space all sized and logistically planned for?

Cost of boards/slabs 300 mm wide compared to a wall truss assembly from smaller wood, and beam work.

I also have concerns with the roof, I don't know if it will hold up...

Yes, the windows and their dimension are the same as the real ones I have.

I don't but it's more than enough to what I planed. I will still have some space if I want to add something.

I'm not sure what you mean with wall truss. I'm not familiar with the expression and googling it didn't help much. I still don't know the price of the wood but I'm thinking I can reduce the cost by reducing the number of vertical boards. If anyone know how wide can I space the boards in order to fill them with slip straw I would appreciate.

My motivation is going down, I'm felling this isn't doable... I started considering using straw bales instead, what do you think about it?

I also have concerns with the roof, I don't know if it will hold up...

You must design for that load.

Yes, the windows and their dimension are the same as the real ones I have.

Are they insulated glass of just plate glass?

I don't but it's more than enough to what I planed. I will still have some space if I want to add something.

Excellent, as long as you have a plan for the space you won't be caught off guard by no having enough space.

I'm not sure what you mean with wall truss.

try these:

http://www.coldhamandhartman.com/upload/documents/BE07-WallSystemOptions.pdf

http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-larsen-trusses

http://www.forestryforum.com/board/index.php?topic=62392.0

I'm not familiar with the expression and googling it didn't help much. I still don't know the price of the wood but I'm thinking I can reduce the cost by reducing the number of vertical boards. If anyone know how wide can I space the boards in order to fill them with slip straw I would appreciate.

No more than 600 mm on center.

My motivation is going down, I'm felling this isn't doable... I started considering using straw bales instead, what do you think about it?

You will then just have the same work in a different way, nothing really changes. You still will have to deal with roof loads, you still will have to deal with frame work for the window. This is why many folks opt for the "timber frame" or "post and beam" approach, then create the thermal mass afterward. Your design is o.k. but by trying to avoid the timber framing, you just made work someplace else, you really didn't make much easier, just different.

Regards,

jay

It's insulated glass.

I received the window frames and drawn them to scale and exactly like they look in reality.

I changed it a little and now I have two questions:

1º- Because it didn't need to be so tall, I decided to take out the wood that was supporting the windows. The question it raises is if there's any problem if the frames are directly touching the foundations, or embedded in them. Illustration can be found on the greenhouse located in the origin.

2º- If you look at the bottom of the window frames you'll see that there isn't anything supporting the glass. The glass is very heavy so I'm not sure what is the best option to solve this.

I'm also considering using wool instead of light straw on the roof. This would make it lighter and would solve the problems with the excessive load.

Hello Bruno,

Thank you for the updates.

I asked about the glass because insulated glass is better, but is also much heavier. That weight will have to have substantial frame work to support it and the roof above.

1º- Because it didn't need to be so tall, I decided to take out the wood that was supporting the windows. The question it raises is if there's any problem if the frames are directly touching the foundations, or embedded in them. Illustration can be found on the greenhouse located in the origin.

The window have to sit in a structural frame of some type, wood, steel, stone, and it should be a minimum of 450 mm off of grade. very well flashed to drain water, or you will loose the frame work to moisture damage in just a few seasons. You could build something that sits closer to grade, but I'm afraid that design would be in stone, and that is beyond the tools you have and your skill sets at this time.

2º- If you look at the bottom of the window frames you'll see that there isn't anything supporting the glass. The glass is very heavy so I'm not sure what is the best option to solve this.

I know you have chosen to not timber frame, but you must frame the structure in something, especially the windows. The window must be framed, they also must be protected from the weight of the roof, and they must be flashed to drain water or any wooded frame work will quickly rot from moisture damage.

I'm also considering using wool instead of light straw on the roof. This would make it lighter and would solve the problems with the excessive load.

If it is not treated with Borates it will become a mess of "wool moths" very quick. It also will be heavy enough to still require a frame work more substantial than what you have.

I like your creativity, but I'm afraid you are loosing you motivation because you are making more work for yourself by trying to avoid certain basic building principles. I don't want to see that happen. So for this next round of thinking, lets just deal with the foundation, it's size, what it's made of, how you are going to build it, and how much time you have left to get this all done.

Regards,

jay

What do you mean with "off grade" and "well flashed"?

About the frame, I'm just trying to use the less wood possible. The back wall doesn't have poles or beams but it has 11 pieces of wood that will help support the roof weight. How do you suggest I should do to support the roof weight on the front wall (glass wall)?

What do you mean with "off grade" and "well flashed"?

Grade is defined as ground level. In architecture you have rough grade, that is the space that has had all the organic soil removed and only mineral soil left. Then you have finished grade, that is the level of the soils when the project is done. This must all be planned for and consider when doing any piece of architecture.

Flashing is the protective cladding on a structure to protect it from weather (water) infiltration. There are books worth of knowledge written on both these topics so, I have only given the short answer.

About the frame, I'm just trying to use the less wood possible.

I understand that, but in the process you could very well be making more work for yourself by doing so. Cobb is very labor intensive, and if that cobb is structural, (or in your case semi-structural) it is more work than if you had a structural wooden frame that formed the bones of the building, roof included. Then used cobb as a thermal mass insulation.

The back wall doesn't have poles or beams but it has 11 pieces of wood that will help support the roof weight. How do you suggest I should do to support the roof weight on the front wall (glass wall)?

with an appropriately sized wooden frame, as steel and stone are outside the scope of the project. That is why I suggested a timber frame in the very beginning. You have a lot of wood in the structure now, it just is in a different configuration.

I would have suggested Thatch, but your roof pitch is too shallow. The roof pitch is not really steep enough for most roofing material to drain water well. This structure you have designed is reminiscent of many I have seen that are buried in the ground with only the front exposed. These structures often fail if not extremely well engineered, do to the weight of the roof, and water infiltration. We haven't gotten there yet, but you have no eaves on the structure? How will you protect the walls from water getting inside them from a driving rain? That is why better built, (longer lasting) structures have eaves

I have read through this several times, and it sounds a little challenging, sorry about that, but it would seem you have a great concept, but are trying to make things work that just aren't going to, or at least not going to without a whole lot of work, and maintenance. I'm still behind you, lets make a list of basics, how long do you have to do this? What is your budget? Then we can examine the actual frame work to build the structure, and the foundation it needs to rest on. What you have so far (correct or incorrect) would take to men at least a month to two months to build, minimum.

Regards,

jay

Jay, about the grade, I'm confused because I see a lot of industrial greenhouses with the glass at grade level. This glass is at 90 degrees with the floor and mine isn't so I'm guessing that's the problem, right?

About the flashing, if you see the sketch you'll see that the glass is protected by the wood frame except on the bottom. The guys that made the frames told that if they framed the glass completely there would be water infiltration on the bottom. I asked them if it was ok to put silicon on the side of the glass, where it rests on the frame, but they said that I shouldn't do it. I don't understand why. In my mind it would only create an extra protection against the water...

I didn't include eaves in the sketch but, like we talked before, I was thinking about doing a "second roof" on top of the first one. It would be spaced to let air flow and bigger in order to prevent rain coming from the sides. This could use independent supports to avoid over-loading the weight of the structure.

I don't know how to use light straw in another way. Everything I've seen/read about it shows the light straw compressed between two wood boards. Being so, I might as well use this wood to double function and serve as skeleton for the structure.

About the budget, I already explained my situation. I don't have a fixed budget because I'm doing this as a volunteer on a farm and the farm owner is the one deciding what is reasonable to spend.
I still don't know when I'm leaving but I still have, at least, 3 more months here. Of course I want to finish it before because my main interest is not the building but what is going inside.

Jay, about the grade, I'm confused because I see a lot of industrial greenhouses with the glass at grade level. This glass is at 90 degrees with the floor and mine isn't so I'm guessing that's the problem, right?

Yes, that's part of the challenge, and then the framework is the other. I have facilitated frames that sat only maybe 50 mm off of finished grade. The frame was a mix of stone and timbers made of cedar wood. With the correct design and material you could even have the glass on grade, but that is much more advanced design.

About the flashing, if you see the sketch you'll see that the glass is protected by the wood frame except on the bottom. The guys that made the frames told that if they framed the glass completely there would be water infiltration on the bottom. I asked them if it was OK to put silicon on the side of the glass, where it rests on the frame, but they said that I shouldn't do it. I don't understand why. In my mind it would only create an extra protection against the water...

With out seeing the actual insulated glass in it's frame work it would be difficult for me to completely asses this. I could say this. If the windows you have are design as skylights, then they many have adequate flashing and protection from the elements. If they have been design for a vertical walls, they are doomed to have water damage unless properly flashed and protected. In many cases, such as you are building, the water must run off and out of the window assembly. If you seal the bottom in the wrong way, you will trap water there because it will not be able to drain away. Try and find some links on the internet that show window details and tell me what you learn.

I didn't include eaves in the sketch but, like we talked before, I was thinking about doing a "second roof" on top of the first one. It would be spaced to let air flow and bigger in order to prevent rain coming from the sides. This could use independent supports to avoid over-loading the weight of the structure.

Good concept, and I do remember that, but your design is becoming more problematic, as it grows in complexity with the different systems it will rely on to function. Why build one building on top of another if you can build them as an integrated system.

I don't know how to use light straw in another way. Everything I've seen/read about it shows the light straw compressed between two wood boards. Being so, I might as well use this wood to double function and serve as skeleton for the structure.

That can work for the walls to a point but then it must function as a support for a very heavy roof. When you are thinking and designing anything, remember that the system as a whole must work in concert with the other components, change one and others change or fail because of it.

About the budget, I already explained my situation. I don't have a fixed budget because I'm doing this as a volunteer on a farm and the farm owner is the one deciding what is reasonable to spend.
I still don't know when I'm leaving but I still have, at least, 3 more months here. Of course I want to finish it before because my main interest is not the building but what is going inside.

I know what I am about to write may seem discouraging, but I don't want to give you poor guidance either. If you had a good design finished, all the materials reading to go, and the tools/manpower to do the work, you will just get this project done in three months if you start tomorrow. I am saying this, not to discourage, but to be honest. If you think you will come back to this location. I would advice to make your goal, finish a good working design, finish the foundation, and material collection, so someone can move forward, or wait til your return to do the rest of the work. Rushing, especially on your first build, does not often give good results.

I see two solutions here: address and solve the problems with the current design or rethink everything and start again.

Personally, I believe that I the problems can be solved but I would like to ear your opinion. I'm having a hard time understanding why does a small construction like this one needs so careful planing. I tough that the size would allow me to build it without going into to the details of construction.

Personally, I believe that I the problems can be solved but I would like to ear your opinion. I'm having a hard time understanding why does a small construction like this one needs so careful planing. I tough that the size would allow me to build it without going into to the details of construction.

Ah yes, a very common misconception. "If it is small it must be easier," as you are learning, this is far from the truth. You still have all the elements of large architecture, then throw in the burden of it being a Green House, and you have a entirely new set of additional challenges with moisture, plus you have added "supper insulated" into it. If you have been building for 10 to 20 years, these things would not seem so challenging, but for a beginner...that's a lot of work.

I have learn that it is really hard to access skill levels over the internet of folks I am corresponding with. You have learned much through this process, so it is a 50-50 split between starting over or fixing your concept, it doesn't really matter. I wish I had the time to sit down and really fix the design, but that would do you any good. I have brought this up several times now, and I think its time to really address it, if you want to move forward. I'm going to state some absolutes about you project and try to get you back on track.

Lets start with these:

300 mm thick walls.

The ceiling will also be 300 mm thick.

You have the windows, so that is taken care of.

Now lets fix things.

What is the foundation going to be made of?

Do you have those materials for the foundation?

Is the site prepped for the foundation?

What size timbers do you have access to, and what species of tree does it come from?

Foundation I was thinking concrete. I already made a ditch on the ground with the area of the greenhouse. I still don't have the timber or the concrete but I can take care of that this week.

So, regarding the actual design, I have to:

1 Space the windows from grade level
2 Find a way to secure the glass in the frame
3 Seal the glass on the window frame
4 Include eaves
5 Include door
6 Add more structural strength

If there's something I'm forgetting let me know.

1 If you look at the last sketch I uploaded you'll see that there's a greenhouse on left side and one in the centre. The one on the left has the windows spaced from the grade. The bottom poles of the window frames are strong enough to support the weight of the window and if the wood boards that sit beneath the windows are secured to the foundation I think it can work as it is. But why does it have to be 450 mm from the grade? I understand that sitting directly on the foundation could create problems but, the way I see it, there's no need to make it go 450 mm apart. Wouldn't it be enough to use some wood beams and create a place for the windows to rest?

2 This is going to be tricky because between the bottom of the glass and the bottom of the frame I'll have maybe 10 or 20 mm. Anyway, like the guys that made the frame suggested, I think that I'll attach metal supports to the frame and let the glass sit on those. I know that when I do this I can't leave any metal sticking out on the bottom that would prevent rain from drain off.

3 Despite what they told me, I've found on the Internet a lot of products like silicon or foams that are used to seal the glass in the frames. Thinking about foam, wouldn't it be possible to put foam on the place where the glass is going to sit and then, before it dries, secure the glass in place? This would close all open space between the glass and it's frame making it air-tight. The excess foam can be cut off when it dries.

4, 5 and 6 are all connected some I'm just going to add some strong beams to the design and upload it to get your opinion on whether it's going in the right way or not.

An update just to see if I'm moving in the right direction.

And another one...

I don't know if I'll be able to get poles of wood as big as those ones but it's just to give an idea of how I'm thinking to do.

I added a pole in the middle of the greenhouse for extra support. I would prefer not to have it there but I think it won't be a big problem.

Foundation I was thinking concrete. I already made a ditch on the ground with the area of the greenhouse. I still don't have the timber or the concrete but I can take care of that this week.

Good, put in the foundation to the specs of you CAD drawing. Can you post photos of the site that is ready for concrete?

1 Space the windows from grade level
2 Find a way to secure the glass in the frame
3 Seal the glass on the window frame
4 Include eaves
5 Include door
6 Add more structural strength

Yes, that about correct.

But why does it have to be 450 mm from the grade? I understand that sitting directly on the foundation could create problems but, the way I see it, there's no need to make it go 450 mm apart. Wouldn't it be enough to use some wood beams and create a place for the windows to rest?

It is called the "splash effect, and the way you have your frame designed you need to be this high because of it.

2 This is going to be tricky because between the bottom of the glass and the bottom of the frame I'll have maybe 10 or 20 mm. Anyway, like the guys that made the frame suggested, I think that I'll attach metal supports to the frame and let the glass sit on those. I know that when I do this I can't leave any metal sticking out on the bottom that would prevent rain from drain off.

Lets deal with this a little latter. I don't know if you need metal or not, but you will have to get the window at exactly the correct angle for the design.

3 Despite what they told me, I've found on the Internet a lot of products like silicon or foams that are used to seal the glass in the frames. Thinking about foam, wouldn't it be possible to put foam on the place where the glass is going to sit and then, before it dries, secure the glass in place? This would close all open space between the glass and it's frame making it air-tight. The excess foam can be cut off when it dries.

As long as water is not dripping on the wood, or through "capillary effect," running in under the window. Flashing may fix this, foam can suck it in like a sponge.

I don't know if I'll be able to get poles of wood as big as those ones but it's just to give an idea of how I'm thinking to do.

I fixed that in my design, you should be able to get 150 mm x 150 mm with no trouble.

I added a pole in the middle of the greenhouse for extra support. I would prefer not to have it there but I think it won't be a big problem.

Not needed now.

This is finally going! I'm excited about it and very very thankful to you.

The foundation site isn't completely done but I'll try to get some photos so you can see how it looks. There are two problems with the site: it's not completely flat and there are some branches that can pose a problem for the overhang but I think both of them can be solved. We'll get to that later.


1. Ok, now I understand It will be spaced from grade level so one less problem.


2. I think I didn't explain myself about this. The glass is still not in the frame. The guys did a wooden frame but they didn't put the glass in it which means that I'll have to do it. If you look at the sketch you'll see that I've made the frame and the window two different components, both of them with real dimensions. You can also see that the frame doesn't have a bottom part, which means that the glass doesn't have a place to rest in the frame. I'll pay a visit to the guys who made the frames and ask them their opinion on how should I secure the the glass.


3. About this I'm also going to ask the guys who made the frame but, to answer you, if I they make foam specifically for isolating windows I'm guessing that they make it waterproof.


You think 150mm x 150mm is enough? I'm sure those can be acquired easily.

And about your design, YES! How didn't I think about that? I guess it's part of the learning process :p I'll use your idea and create a new version of it with all the updates and post it maybe latter today or tomorrow

Ok, using your ideas I changed the sketch and also added a door on the right. I'm not sure if the door will work like this but take a look please.

I have some photos...

Photo 1 is the building site of the greenhouse
Photo 2 is also the building site but specifically the corner with least space and which is on the lower part of the ground
Photo 3 is a picture of the bottom of the window frame as it is now. I'm still painting them so I haven't started thinking how I'm going to secure the glass but as you can see there is no built-in support for it

Good, send them, I really would like to see them before I respond again. Also, the door is really in a poor location, probably the least viable one. In the back wall, centered or at one of the ends.

I edited the previous message and posted the pictures there