cob in the city - advice request

Hey everyone, brand new to the forum, but loving what I've seen so far

I'm based in London, UK and I have a small (6mx8m) concrete 'garden' surrounded by brick walls on three sides. Half the garden is given over to a shed, which is nothing more than a flat roof that covers the full width and half the length of the garden, and a 'wall' made of bits of old doors nailed together...

I'm intending to pull down the wall and replace it with something more attractive and insulating, and turn the shed into a useful, proper indoor space. I got very excited about the idea of cob when I learnt about it recently, but I'm not sure that it's appropriate here. Beyond the issue of cheaply sourcing straw, clay and sand in the city, I have a few concerns that hopefully someone here can help me with:

1. This won't be a load bearing wall - Does this matter for stability?

2. The ground is concrete - Is this an issue in anyway?

3. Is cob a poor choice for some other reason?

Any advice will be greatly appreciated, thank you for reading

Hi J.K.,

You are from the "land of Cobb" and they are great at it there!! Many traditional programs and work shops there on cobb, so I believe you are in good order to sort this out.

I need to see some picture to tell you anything about if LB is going to be an issue or not.

If the concrete gets wet, it can lead to wicking moisture into the cobb wall matrix.

Can you post some photos and maybe a little sketch of what you are thinking of?

Regards,

j

Have you considered wattle and daub or light straw clay? Cob is not particularly insulating. Since you are in a city, I was thinking perhaps a wall of used wooden pallets stuffed with light straw clay then finished with clay plaster?

Hi Andrew,

I like your idea, as a Timberwright, I too lean in your direction, however I am not sure this structure will warrant such methods. I would also point out to make "Wattle and Daub" which is nothing but cobb with a timber frame and lattice structure, can be of course be much stronger structurally then just cobb, yet both can yield the same level of thermal efficiency depending on how they are facilitated. With slight modification you can achieve much better results with both methods. I also get a sense that the goal here is as much vernacular the Isle's traditional structures as it is a goal of just recycle and natural.

Regards,

j

Thanks for the responses!

Jay C, I've attached some pictures, you'll have to envision it without the ivy, as it will be getting trimmed back very shortly. I'm probably going to leave it on the top of the roof though.

Andrew, I'm intending to use wooden pallets inside the structure for built-in shelving and some other furniture - I hadn't considered them for the wall, but it sounds promising.

One of the reasons I was interested in using cob is that I was intending to embed glass bottles in the wall to allow lots of light through. My building is four stories high, and it blocks the direct sunlight for much of the day. The other is that I wanted to build some curves (extending the wall out a little to make the inside space larger), though I suppose there's no reason I couldn't fashion a curve using pallets.. right?

I'll get a sketch of what I'm imagining up soon.

Thanks again guys

Hello,

With those photos and your comments I support Andrew's thoughts and a few more ideas as well. I will wait for a sketch to get a better understanding of what you plan, as I have questions,concerns about roofing, water management and drainage challenges, and overall affect this space will present in form and function.

Regards,

j

Hi again,

Sorry for the delay and apologies for the quality of the sketching. The dotted line indicates the boundary of the roof, and the red lines are where I would like the new walls to be. I am dividing the space inside, the smaller left space will be for tools and supplies, the right space will be a general purpose room.

The top view image shows where I would like the doors to the spaces to be, probably not very important right now.

I am intending to use corrugated plastic sheeting for the additional section of roof required. I will put a drain around it, and have the roof at a downwards angle, overhanging the new wall. Any thoughts on that?

Jay C, you are correct that the primary philosophy here is to recycle and remain as natural (and cheap within reason) as possible. I am not attached to the idea of any particular building method, nor am I trying to necessarily be traditional in my approach.

Thanks again

Hi J.K.,

I work in metric so your measurements are fine for me...yet there seems to be some incongruency? Can you clarify the measurements? Would it be possible for you you to do a side and end elevation with the way you perceive the roof?




I believe without knowing and designing for elevation views, and proper slop of roof(s) you could have issues in the future. I would either draw (have drawn) or create a scale model of what you plan. This way you would avoid any unforeseen or thought of issues.

Regards,

j

Hi,

Yes, I'll take some more measurements, the roof must have a slope to it, and I see now my numbers don't add up on each side...

Another clarification I should make is regarding the four 47cm elements on the diagram - they aren't windows, they're protruding bits of the brick wall, one brick deep. I think they used to be supports for a previous roof. I will post new diagrams (I might even try to use a computer to make them this time!) including a side elevation.

Andrew, would you be able to point me in the direction of a project that uses "wall of used wooden pallets stuffed with light straw clay then finished with clay plaster"?

Thanks again

I would suggest you do a search for pallet straw clay on the internet. There are many examples available. I found a cob group in London and asked them if they might chime in. You can visit their website at: http://www.cobinthecommunity.org

Good luck.

Hi Linda,

Thanks for joining the conversation, I'm also in North London, Camden to be more precise. I'd very much like to meet up I'll PM you with my details so we can arrange something.

Let us know how things go. I am guessing you will now have plenty of opportunities to experience cob.

On a slightly related subject, as I was looking around for examples of pallet construction with light straw clay infill, I remembered something similar I had come across a few years ago, but I couldn't remember for sure what is was. Today, I made a concerted effort and managed to stumble onto it again. It was the Juanita Briones home in Palo Alto, California (finally demolished after years of protest). She had it built in the 1840's using a rare, for California, technique, a timber wall covered with lathe and filled with adobe (cob). The article I read did not put a name to the technique, but there is one, bajareque macizo. It is quite common in Latin America. (Jay, the Gutierrez document gives a thorough description of bajareque hueco, or hollow wattle and daub. He does not recommend traditional macizo of adobe because of higher inertial force, but I think light clay would be fine). Here are a couple of documents I downloaded that describe bajareque construction: Construccion de muros en tapia y bahareque, and Recuperacion del sistema constructivo en la tecnica del bahareque en la contemporaneidad.