Monday, November 5, 2012

Timbrel Stairs

The crew have been busy at Kisongo with the Widow's hall and houses (two now) since May.  I got Dickson to add a mason and finally I got Dickson back full time, on the groined vault house for awhile.  ( While the other mason Goodluck puts up the short walls on another vault in Kisongo.

I finally bit the bullet and went ahead this week with a "new" technology for me.  Timbrel or Catalan Vaults.

Where I want to use this technique is on the top half of the stairs in the groined vault house. Where the brightness is up to the top floor.  




I made a post about this technique, and I tried some trials and found the gypum plaster works for the first layer.

I know how to do timbrel vaults  but the catenary shape can vary, so I kept putting it off  and off and fretting about it.  I bit the bullet a weekend ago and traced the shape on some reclaimed chipboard.  The load on the arch will vary so I worried about that until i realized when someone is standing on it it would also change the line of thrust so i figured at any time the LT will stay within  1/3 of the arch.
So here is from the side, the first of the three layers. tomorrow we remove that chipboard.


Below is the view from below.  After removing the side "wall" we will add another row on both sides. the plywood is our template and we use that wall to "glue" the tiles.  We need more suport.




And what it looks like on top of the arch.
As I said we will add two layers on top of this one, different bonds, and then the treads sit on top of the vault. The mortar now will be cement-lime-sand.  Each layer is overlapping the bond below.  Should be fun.

Edit 7 November 2012:
This is a good link about Timbrel vaults.  It explains more and better than I can.

You too could have a roof/ceiling like this in your house.




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4 comments:

  1. Matt SevignyNovember 7, 2012 at 2:34 AM

    Are the bricks next courses going to be laid as shiners or stretchers? It would scare me to load an arch with the brick oriented on the flat.

    I'm curious about the gypsum too. How do you get it, dry or like sheetrock mud? How is the bond? It seems like it would be lime like...soft but flexible.

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    Replies
    1. MzunguErikiNovember 7, 2012 at 5:25 AM

      HI Matt, thanks for questions.

      All three layers of tiles are laid flat. This is the way the Catalonians do it, and Gaustavino did it this way all over East Coast (boston public library). As it is the first one I put some rebar in between first and second courses. Gaustavino talked about the cohesion effect that made is so strong.

      I am using simple gypsum plaster, like you use when you use sheet rock for the joints. It gives no structural value. I use it becuase it sets fast, in fact we let it set for ten minutes and use in ten.

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    2. MzunguErikiNovember 7, 2012 at 5:52 AM

      Gypsum is used only on the first course, then lime-cement-sand

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  2. Matt SevignyNovember 7, 2012 at 10:06 AM

    Please post that link you sent me. Very enlightening and informative. After reading the technology behind the timbrel arch it is something I have to try someday...yet another thing for the bucket list.

    Two quotes I really love in the beginning of the article...

    "the weak tensile strength of brick was compensated for by superior craftsmanship."

    "The "timbrel vault" allowed for structures that today no architect would dare to build without steel reinforcements. The technique was cheap, fast, ecological and durable."

    There are a few organizations that are fighting to have drystone work recognized as a valid method for of building walls...which it very much is. But I think it is a bigger travesty that this form of building (beautiful vaulted ceilings) has been pushed aside...with fast and cheap in place of craftsmanship and long lasting.

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