10 reasons

Brent & Janelle and Grey came this week - it was wonderful. Here is Brent's take on the week...


10 Reasons The Concrete Roof Will Stay Standing:

Reason #1:  There are many concrete roofs in Ixtlan that are not falling down.  One I know of sags a little, but the builders admitted it is a rebar issue and Grant ensured we will not have that same rebar issue.  We think.  We’ve set out to hold approximately 12 tons (18 yards at 150 lbs per cubic foot) of concrete overhead for say, 30 years or more, so we’ll take any encouragement available.  There is no doubt, when looking around any Mexican (or any developing country for that matter) town, that builders have a knack for using what is available and perfecting it into a repeatable system.  Reinforced concrete is the most common building system in developing economies because the components are so readily accessible.  Small rocks, big rocks, water, air, and Portland cement are all you need, at least for floor slabs.  When the slab is a roof, steel is required as well, but more on that later.

Reason #2:  Tree- felling Indians.  I’m suddenly curious what a Mexican Indian (what?) yells when he fells a tree.  ARBOLES!  He could also yell PUNTALES! (poon-TAH-lace!) because that is what the felled tree eventually will be.  Yes, I am going to continue using the verb ‘to fell’ because it is fun.  Once the trees have been felled, they are stripped of their branches and cut to the approximate ceiling height of a prospective new concrete roof.  The already-felled puntales are placed on roughly a 3’ by 3’ grid inside the house to support the formwork for the roof.   This makes the interior of Grant, Hannah, and Ivory’s home (hereafter GHI) look more like a forest of unfelled trees than a house.  This is exactly how this same process is executed in the US except  the puntales are called ‘shores’, they are made of steel  not logs, and there are no tree-felling Indians.

Reason #3: Load Path.  This is one of the most important reasons, but listed early in this list because it is likely not of general interest to typical readers of this blog and we need to keep moving.  The goal of the structural system is to direct all forces from the roof down to the foundation.  For example, if a chivita was standing above the kitchen the load path would be as follows:  1) feet of the chivita to 2) concrete/rebar to 3) embedded rebar ‘beam’ to 4) steel beam under the slab to 5) a concrete column in masonry wall to 6) foundation below.   If you learned nothing from this little description, just remember that a ‘chivita’ is a dwarf goat.  

Reason #4: Jose.   I don’t know Jose’s last name though I did attempt to find out.  It went like this (translated to English, my native language):
What I’m trying to say: Jose, what is your last name?
What I’m actually saying: Jose what is your nickname?
Jose:  Ah, I have many!
What I’m trying to say:  Which last name is your favorite?
What I’m actually saying: Which nickname is your favorite?
Jose:  <smiling, avoiding the question>  What is your nickname?
Me:  Young!  It’s from Germany.

We both went away smiling and happy with our conversation.  He never did ask how I got a German nickname.  And I’m not actually sure that ‘Young’ is German in origin, but I don’t know the Spanish word for ‘Switzerland.’  Anyway, Jose is likely the single most important reason that the roof will stand up (besides #10, but that goes without saying (ever notice how things that go without saying don’t actually go without saying?)).  He is the foreman on-site and Grant is the owner/designer/cm.  The key is that Jose has done this before, he is trustworthy, and he is seeking to do a good job for GHI.  Construction quality is rooted in how much you care.  The best design, engineering, materials, and management cannot make up for a construction worker who does not desire to do a good job (there is a spiritual metaphor here somewhere).    In working on his crew for a few days, it is evident that Jose does care and is committed to doing the job right.  I estimate that there are over 4000 places on the concrete roof where 2 pieces of rebar cross and must be tied together.  Every time I would ask Jose ‘Todos?’ (All of them?), he would answer ‘Todos!’  This is one of our typical technical construction conversations.

It wasn’t just Jose’s attention to detail that impressed me, but also his willingness to lead and teach.  I learned the Mexican method for tying rebar (which I find more versatile and superior to the US method) as well as a few new Spanish construction terms.  Ever the construction manager, at one point I was waiting on Jose while he was doing a job that I could have been doing and we had this conversation:

Me: Tu, alli. yo, aqui. (You, over there.  Me, here)
Jose:  Ah, si.  (Ah, yes)
Me:  <pointing at Jose>  Cosas mas importantes! (More important things!)
Jose: <continuing to work ahead so I could follow> Yo, Moises!  Tu, la puebla de Israel.  (Me, Moses!  You, the Israelites!)

Our communication was limited, but this we both understood.  He was leading and I was following.  And we’re heading toward the promised land (and a concrete roof).

Reason #5: Rebar. . .lots of it.   Since concrete has little tensile strength, steel reinforcing must be added in order to span from wall to wall.  GHI’s house includes long spans of about 12 feet.  Not a great technical challenge, but still a design issue that must be addressed with care.  When I arrived on the jobsite the first day, it was just about time to begin installing rebar and I was curious to learn the local strategy.  I believe I can now say with confidence that if this was a project in the US with a structural engineer- drawn rebar layout drawing, it would be very similar.  Basically, they have placed 3/8 inch diameter rebar on 6 inch spacing in both directions.  There are several internal reinforcing ‘beams’ made from rebar cages that will be embedded in the slab.  One way to work on learning a foreign language is state the obvious many times and during the installation of the rebar there were many opportunities:

Me:  Mas barias?  (More rebar?)
Jose:  Ay, mas barrias.  (Ah, more rebar.)
Me: Barias y barias y barias y barias. . . (Rebar and rebar and rebar and rebar. . .)
Jose:  <chuckle>

Reason #6:  Sombrero Grande (large hat).  Grant loaned me a large straw hat and I feel strongly that it played a grande role in our effectiveness as a rebar installing crew.  Obviously the Mexicans felt much more at ease having a gringo around because I was wearing a gigantic hat.  It provided a great deal of shade for me from the afternoon sun and sometimes shade for those working nearby as well.

Reason #7:  14 Day Design Strength.  Concrete begins curing as soon as it is mixed through the heat of hydration process.  It continues to cure throughout its life, getting stronger over time (another spiritual metaphor?).  Concrete mixed from typical Portland cement will have about 80% of its design strength in 14 days, and 100% by 28 days.   The plan for GHI’s house is to allow the concrete to cure for 15 days and then remove the puntales.  PUNTALES!  Just kidding.   There are ways to engineer a concrete mix in order to be able to remove the supports much quicker.  However, they plan to bucket 18 cubic yards of concrete to the second floor by hand all in one day.  After that, I think 15 days of rest sounds about right.

Reason #8:  The Recipe.  Mixing concrete is like baking a cake.  The key to success is in the ingredients and the ratio.  I’ll confess I really don’t know the mix design (recipe) for GHI’s house.  I attempted to ask about pounds-per-square-inch (psi) then realizing it would be metric I switched to megapascals (MPa).  The answer was something like 1 bucket rock, 1 bucket sand. . .  We were not speaking the same language (get it?).  Please refer to Reasons #1 and #4.

Reason #9: We have plans for this house.  This reason is not really causal, but more based on 2-year-old logic, with which we are very familiar.  ‘I want it.’  Why?  ‘Because I want it.’  Thus, we want this roof to stand, this house to be finished, and this mission effort to continue because we had a great time and we’re already thinking about next year!  Grey and Ivory got along great, but they don’t seem to share many similar interests.  Grey liked the tractor, talking to Ivory, dirt, the chickens, the volleyball, and playing outside.  Ivory was more interested in sleeping, eating, being cute, and wearing pink.  We’re hopeful for future years where the children play together nicely in the front yard of the new house, while we fellowship and sip manzanita on the veranda.  We’ll sit back and wonder to ourselves: what is a dwarf goat doing on the roof?

Reason #10:  Prayer and Providential Provision.   I was told once to always avoid alliteration but sometimes it just works.  About 10 years ago I was in Juarez (back when it was less dangerous) on a work team that built a few small houses.  During the work day, we always had a ‘prayer chair’ which continually occupied at least one person who was taking a break from work to spend some quiet time in prayer.  The combination of Mexican sun, mild construction frustration, and a penchant for college-age rhetorical questioning gave me pause to ponder:  would it be more effective to have 9 people praying and 1 working?  What about 5 and 5?  You can sort that out on your own; the point is that we seek to be faithful. We try to put in enough rebar.  We listen to those who have done it before.  We work together as a team.  And we pray.  Except the Lord build the house, they labor in vain that build it.