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Tuesday, March 2, 2010

Making Mud Bricks (Omani Style)...


I'm teaching a class in 'Architectural Conservation & Preservation' in which we've decided to take a slightly skewed take on the topic, more of that later, but to commence this valid subject matter we're going to attempt to build a 1:5 scale space using traditional (Omani) mud-bricks. To allow us to understand what this would actually involve we managed to find and visit (thanks to my industrious and well connected students Ali and Khaled) an actual mud-brick making facility at Bahla Castle, an ongoing restoration project taking place approximately thirty-five kilometers from Nizwa. Apparently the castle's/ fort's restoration has been going on for a few decades by now, which makes it (particularly in the context of the Gulf) a unique and commendable project indeed. During our visit we had the opportunity to inspect the mud-brick making process from start to finish, the stages of which are outlined (in brief) below...

(Please click on the imags to inspect them in more detail)...


Pits adjacent to the site where the clay is initially settled and stored...


The process starts by bringing the clay to the site where it needs to be stored in adjacent clay-pits (as seen above) for at least a month before it can be used. It has to be wetted regularily...


A pile of clay intended for bricks...

Once 'aged'/ settled enough to use, the clay can be adapted to two primary uses - as bricks or as mortar and screed (which seem to be more or less the same). The clay for bricks is thicker (seen above), more viscous, than the clay used as mortar (seen below) which is stored in dug out 'cubicles' also located next to the site.


The clay used for mortar and screed...

The clay used as mortal can seemingly be used as is, whilst the thicker clay intended for bricks needs some post-processing. This involves mixing it with dry straw, done manually by foot (in a somewhat similar fashion to crushing grapes for wine - see image below) as well as shovel, at a roughly 3/4 clay - 1/4 straw ratio (or 1 wheel-barrow of clay, 2 bucket fulls of straw). This mixture is allowed to settle for a day...

Mixing clay, water and straw for the mud-bricks...

Their boots act as evidence of their tramp-led/ing toils...


Delivery of mixed (brick making) goods...

The mixed clay is brought to the brick making site in wheel-barrows, where it is put into molds (see below) and allowed to dry for five days in the shade and two additional days exposed to the sun. The most common brick size is 30 x 15 x 15 altough the option of making them 35 x 15 x 15 or 13 x 10 x 15 also exists... The workers at the Bahla site made on average between 250 - 400 mud-bricks a day...

Making mud bricks...

The mud-brick making process - The inside of the mold is lubricated with a watery coat of clay; the clay is packed into the mold up to its rim and the top surface is flattened and smoothed by hand; the mold is lifted off the brick and the process is repeated...

A few examples of different, both wood and metal, molds used...

The mud-bricks are allowed to dry for five days in the shade, and two additional days exposed to the sun...

Included below are some additional images from the Bahla Castle/ Fort in which restoration the bricks are used.

Regarding our project we eventually plan to take what we learn from making the bricks ourselves and expand on the remit to hopefully also include a updated/ adjacent take on what using such materials and processes could actually entail. This might involve experimenting with alternative binding materials to straw (look at GRC as an example) or, say, apply some lessons from contemporary rammed earth construction (updates will be included as the project progresses)...

Bahla Castle/ Fort...


Watch tower...

Smiling wall...



Above and below - examples of various textures and aggregates used in the various mud-brick walls at Bahla Caste/ Fort...

7 comments:

Jassim said...

This is very interesting. My favourite is the image of the tarnished boots depicting the evidence of an eloquently barbaric job well done. This revival of a classical building method looks promising.

Thomas said...

Thanks Jassim...

It's a dirty job, but someone's gotta do it... Plus it's fun to muck in the mud...

Tom

Jazz said...

Thomas,

I am working on a Gathering Space for a Native American in Iowa. We are using old Scottish stone masonry methods. He has a project that he will be working on soon and wanted a different sustainable construction method, I told him about this Omani mud-brick method. He is enthusiastic about it and wants to implement it, are there any more specifics you can provide about the structural integrity of this method: how much load it can carry, if it needs buttressing, how were roofs connected and what did they span, how do you make a straight wall etc.
If you could assist me with this vital information it would be immensely appreciated.

Jassim

Thomas said...

Hi Jazz,

Sorry for the delayed response - busy times...

Unfortunately I don't have any more specific info regarding the exact parameters of Omani mud-brick walls, as they seem to be based on general rules of thumb and information passed down through something closer to an apprentice process... There might be some books out there covering the subject, but I haven't come across any, at least in English, that explain how such structures were/ are constructed. Most of them, however, seem to have foundations made out of stone blocks onto which the bricks are laid. The wall thicknesses seem to range from roughly 300 mm to up to a 1000 mm (depending on the use and height of the building). The mud used for bricks themselves, the mortar and screed seems to be similar, but, apparently, sourced from slightly different spots. We got our mud for the bricks from a materials distributor. We used the same mud as mortar and sourced the screed from one of m students farm, where we took the mud from a patch near the roots of a tree (apparently the moisture content is slightly different from such mud than the already dried one bought in sacks). The mud bricks seems to be adapted to a wide variety of building types, ranging from small residential buildings to large forts (see Nizwa fort, or the Bahla fort). Often perpendicular walls are used for buttressing (i.e. more a question of the spatial layout than separate buttresses). The spans for the floors and roofs seemed to be predominantly (initially at least) determined by the length of wood (tree trunks) the builders could access rather than any (practical) or aesthetic concerns...

There are a few books by and about the work of Hassan Fathy that you might find on interest and relevance...

Good luck with your project..!

Tom

Omani Princess (not Omani LOL) said...

Hi Tom,

Wow, interesting post. Actually, I myself wanted to make a book in English documenting the process, and I have my own personal project, the restoration of some old mud-brick village houses in Oman, to use to jump off from.

I was wondering if you could answer some questions for me. My email is OPNO_princess @ hotmail. com [no spaces but I get spammed alot] if you wouldn't mind answering them.

Number 1 would be, can almost any kind of mud be used to make te bricks?

Number 2, which is the EXACT ammount of mud to straw + water measurement for your average brick?

Number 3, Omanis I asked who still use this building method said they lay the bricks while they are STILL wet onto the foundation, so I wondered what was the average drying/ time before construction.

Number 4, to make how high a structure, what thickness of foundation is needed.

I will probably have more questions AS I go, so if you could share your contacts in Oman for the projects of restoration, I would love to volunteer and learn the art on my weekends here in Oman.

I want to photograph, diagram, and write about the process in a how-to way that anyone could follow, as I restore a few villages houses in my friend's property.

Also, I know how to make sarooj (stronger than the mud bricks and used as a mortor), and wanted to know how this was applied to the fort walls in Oman to get them so bloody smooth. My attempts at making a smooth finish on the sarooj have been less that the achievements of the Ministry of Tourism in Oman. Thank you!

Thomas said...

Dear OPNO,

Sorry for the delay in responding – it’s been a busy week... I tried to send you an email to the e-address you provided, but it bounced...

The answers to your queries are included below...


Number 1 would be, can almost any kind of mud be used to make te bricks?

The mud we used to make our own versions of the (mini) bricks was sourced by one of my students (see: http://smarchitecture.blogspot.com/2010/03/making-mud-bricks-omani-style-ourselves.html ). It came in its dried version in sacks, so I assume it is commercially available and should be fairly easy to find. The hay we used was also apparently made specifically to be used in the making of mud bricks... If I remember correctly we used the same mud for making both the bricks as well as the mortar, but for the screed (the outside, smoothing, finish, we had to use a different type of mud, one with apparently a higher moisture content which allowed it to dry without cracking (as much)...

Number 2, which is the EXACT ammount of mud to straw + water measurement for your average brick?

I believe the ratio was always determined more or less by ‘touch’, i.e. When the clay-water-hay mixture’s consistency ‘felt’ like it should (determined based on experience) to the person mixing it, it was considered ready... But, as explained in the blog-entry, the ratio is roughly 3/4 clay, 1/4 straw (or 1 wheel-barrow of clay, 2 hand-held buckets of straw)...

Number 3, Omanis I asked who still use this building method said they lay the bricks while they are STILL wet onto the foundation, so I wondered what was the average drying/ time before construction.

The mud bricks we made and used were dry. As explained in one of the image captions in the blog entry, the Bricks that were made at Bahla Caste were initially dried in the shade for 5 days, after which they were moved and exposed to the sun for at least an additional 2 days – after which they could be used in the castle’s construction...

Number 4, to make how high a structure, what thickness of foundation is needed.

It depends. Higher structures need thicker walls (at some places the foundation thicknesses of the walls can be close to a meter), lower structures a bit less. It also depends on what the building is used for – a fort needs thicker walls, a residential building can get away with a bit thinner walls, as well as what materials are used in the making of the foundations. Quite often they’re made by stacking large rocks, on top of which the mud bricks are laid... But it seems like any wall has at least 2 layers of bricks, usually based on the set proportions listed in the blog entry...

Hope that helps...

Best of luck with your project...

Tom

Omani Princess (not Omani LOL) said...

Thank you Tom!

I will link to what I find out. Thank you so much for your time.