# GROINED VAULT III- FAILURE? HUMBLE PIE? or GREAT EXPERIENCE?



## Fundi (Jan 5, 2009)

If you have not seen the picture post “Groined Vault II” read that first.
http://www.contractortalk.com/f90/masonry-groined-vault-ii-104372/

(blush) :blush: first. 
Second I apologise this is long, but this is a good place to document my experience, as maybe someone, sometime will benefit from it.

Third I invite you to be critical of the work we did. Now when I look at the pictures I say “man that was wrong.”

Making a barrel vault seems easy now.

If we were better craftsman (like many of the rock masons on CT) we might not of had this problem.* *A big problem.** On the other hand after examining, thinking about it, and talking about it with an architect, engineer, *I AM REALLY GLAD IT HAPPENED*. We learned a lot and it is in these situations a person grows. We have to start over on the upper story, all because of one, maybe two, bricks failing, which caused 5 TO fail 2 mm each and now we have this.








I was also careless .

And maybe I needed corrugated ties.......... LOL

WHAT HAPPENENED:
I was called by Dickson the mason building the large groined vault. "Can you come by as there is a crack !" He said there is no immediate danger but serious. It was hard to understand from his explanation. Saying it had “sagged” also.

After the initial feeling of : we failed, lets build a normal house , make a boring roof like my neighbor, it is just too complicated, and it will have all fallen down by the time I get there.

I get there and see the some arches have split apart on two of the vaults and there are some cracks in the groin bricks on one corner near the bottom. From outside on the ground it all looks normal......


This is the first thing I see when I go up the stairs to the first floor. A separation of arches on one vault.








Then I see this in bottom of one groin:







The stretcher third row from bottom failed and and sank, then ones above cracked.
I suspect the header above was concentrating force on its' edge.

And from the other side.


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## Fundi (Jan 5, 2009)

WHY?

The header visible (first pic) was not properly cut so weight was on corner on the brick below. The stretcher should of extended to be flush with the brick above and not the one below. The mortar in the triangle between stretchers and header above should be completely filled and at least in the first ten rows cement, not clay/sand.

That stretcher third from bottom is not our standard brick, and was not made by slop method, but rammed in a hand press. I think the pressed brick was not as contiguous as a slop brick, and hence weaker. Note the size difference. Non standard brick made 24x11x11cm instead of 7cm. It has more cracks in it than a normal brick. I was thinking as we would be cutting the groin brick it would be better if thicker.
Not all bricks in the groin lay flat on the brick below (complicated to cut), so there was a pressure point and it snapped the brick.

We inspected and inspected and have these observations:
-one brick failed in a groin, when it failed the bricks above also cracked. 
-as one groin sank the arches seperated but were still arches.
-This groin was the first one we built, and we should of torn it completely down.
-dont use experimental bricks, explained above. 
-groin pieces should be well burnt or "clinker" bricks preferably
-groin pieces need to be perfectly fitted
-no pressure points.
-immediately fill in any voids, so do pointing as you go along, or next day.
-keep reminding yourself that those first ten groin pieces are carrying the whole load of the roof. paste that saying on the wall.* In this case the first groin pieces are carrying about 2.2 metric tons!!!* Now I have tested our bricks and they can carry 3900kg before breaking, but what I didn't remind myself is that if you have not perfectly placed a groin brick then you have weakness. 
-we catelevered out from the bottom. Cantelevering is okay, EXCEPT NOT A GOOD IDEA IN A GROIN. Start wide.

The groin pieces in the lower third have to:
-be clinkers in the cornor
-cut precisely
-extend out past the groin on the bottom side so the top of brick supports the brick above completely
-no sharp edges of bricks resting on a brick. flat against flat.
-we are plastering the outside immediately . Makes everything a bit more cohesive.

When building an arch, and even an arch as part of a groined arch, weight is not so critical, but groins in the bottom have enormous weight.

However if we would not of ripped out the groin we would not of had the failure as early that taught us other things. We are more careful now.

Later on we learned to extend the groin brick way past the brick below, so when the line above is laid it rests on that brick completely. Also not the detail of filling in the triangle gap, we “forgot” to go back and fill those at the bottom, were going to do that later. 








I don't feel like showing this picture, but I will in the hope when someone else trys this when they retire they don't do foolish stuff like in this picture. Now when I look at this I cringe and think. “Why did I allow that to stay?” I will show a picture in next few days of the replacement.







Instead of spreading the weight i concentrated it more.








This above was totally stupid. ½ the brick sticking out. Rule is 1/3, but in this case there is a drain, should of put a steel pipe and build over the drain. So that the base of groin is wider and weight more spread out.

I have learned alot in the past few weeks and will learn more in the next week. In the end it is good it happened now, and what we learned is big. True, we don't know what we are doing, but we are "finding a lost art" “reinventing the wheel”. 
Hopefully what I learn can be used by others.

We put more scaffolding and boards all over. Before tearing it down we piled bricks on the arches with no cracks, 25% more than we would be putting up in the remaining arches to finish. left it for a week to see if the other groins would fail. They didnt. no brick failures in the bottom of the groin, but the two arches slowly kept spreading.









In the end it makes me respect the arch even more. It holds up even when there was a failure.

Will the next one fail? 

We are almost a week into the new one. Still on the bricks going flat

I wonder what kinds of failures they had 500 years ago?


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## Fundi (Jan 5, 2009)

*Why not use formwork and ribs?*

Why not use ribs?

I have two reasons for building vaults and groin vaults. 
-I want to find the cheapest way to build a vaulted roof. Form work increases the cost, and relies upon wood. I think I can make a simple vaulted roof cheaper than a wood truss and corrugated iron roof.
-They are incredibly attractive.

Someone else asked, what was the reason for the ribs? To hide the difficult joint or structural reasons, or to make building easier? I guess we dont really know. Ribs will basically make it more expensive. Stronger possibly?


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## Fundi (Jan 5, 2009)

*After a weeks the groins look like this now*

So we started all over after taking it down. This is after about one week, each groin is like this. we are going higher with the bricks perpendicular then horizontal arches.








Better?

My camera was stolen so taking pictures with the damn phone.

Top half not pointed.


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## TheItalian204 (Jun 1, 2011)

I would like to express my gratitude. This is definetly a lot of useful information and priceless experience that I possibly can use in the future.

However,how come you did not consult here before proceeding?


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## Rockmonster (Nov 15, 2007)

Fundi said:


> I wonder what kinds of failures they had 500 years ago?


You can bet they had plenty. A great show on the construction of some of the great Cathedrals played PBS recently, and showed some of the engineering 'lapses' that they had.......I would guess that there is no substitute for experience here, and there aren't a lot with piles of experience here since Guastovino I'm guessing......I give you a lot of credit for going for it. I'll bet if you brought out some random structural engineer, you might even see a fair amount of head scratching going on.......Nice posts, thanks......


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## Fundi (Jan 5, 2009)

TheItalian204 said:


> However,how come you did not consult here before proceeding?


Thanks for gratitude Italian. I spent couple hours writing it.

Over the past year i have posted and a year ago i specifically asked about the groin piece and got some feedback, but more on the lines of to use formwork or making ribs. So I kind of figured I had to experiment. However i had intended to post this more than a week ago but got sidetracked with work.

But now I am consulting, please any constructive thoughts. take a couple of bricks and cut them and you start seeing the complexity, but maybe someone can come up with a better cut.

rockmonster- luckily there is an engineer/architect here in town who only scratches his head a bit. But most engineers dont even know what I am talking about, they only know reinforced concrete.


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## JBM (Mar 31, 2011)

Fundi, im sorry you experienced troubles with this project, but I think I speak for everyone, this is one amazing feat you are building. So, any set backs on a masonry marvel like this are only a bump in the road! This is truly one of those pieces I am in complete amazement with, hats off to you!


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## 6stringmason (May 20, 2005)

What JBM said!


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## wbr (Feb 19, 2011)

Rockmonster said:


> You can bet they had plenty. A great show on the construction of some of the great Cathedrals played PBS recently,


I caught that,it was on Nova,"Building the Great Cathedrals".
Good stuff,pointed arches,flying buttress,ribbed vault.

http://www.pbs.org/wgbh/nova/assets/swf/1/arch-physics/arch-physics.swf

That double barrel is pretty cool Fundi,
you have a lot of patience.
Thanks for posting it.:thumbsup:


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## Diamond D. (Nov 12, 2009)

Pole sana. :sad:

Sorry to hear of your misfortune.

Just a thought, though...
Could you have the corner bricks made in that shape?
Around here, you can have almost any shape made.
Especially, considering the number you will need.

Although, I'm guessing the shape changes as you get closer to the pinnacle.
If that's the case, I think as you said, as long as you fill all voids, solidly, and allow to cure somewhat, as you proceed, that that would more evenly distribute the weight.

Also it probably wouldn't hurt to add some support during construction.
I would guess that the weight of the unsupported groin, was responsible for pulling the arch apart.

Bahati Nzuri,
D.


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## Fundi (Jan 5, 2009)

Diamond D. said:


> If that's the case, I think as you said, as long as you fill all voids, solidly, and allow to cure somewhat, as you proceed, that that would more evenly distribute the weight.
> 
> Also it probably wouldn't hurt to add some support during construction.
> I would guess that the weight of the unsupported groin, was responsible for pulling the arch apart.
> ...


Yeah i didnt think of that . let the pointing cure somewhat. although the groins take so much time that we build slow. It is one week now and we are up to 6 feet only in each cornor.

Not sure about the support. You have to be there but I think even as you are building the forces are down, so if it is right supports arent needed. maybe after work puttin a jam in between the arches would help. I bet if we would of built faster, and closed it all up even with the crack the whole structure would of carried the one cornor! Seriously. 

I manufacture bricks, but like you said they change shape as it rises. So not worth it. And it is actually onl.y 200 bricks that are cut for groin. 

where did you learn kiswahili?


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## Kris Johnson (Dec 20, 2013)

Fundi said:


> Why not use ribs?
> 
> I have two reasons for building vaults and groin vaults.
> -I want to find the cheapest way to build a vaulted roof. Form work increases the cost, and relies upon wood. I think I can make a simple vaulted roof cheaper than a wood truss and corrugated iron roof.
> -They are incredibly attractive.


What about Nubian vaults? (sorry if this has been suggested before) They fit both criteria. A quick google or youtube search for Nubian vaults or (la voutte Nubian) will give you a lot of info on the technique.


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## Fundi (Jan 5, 2009)

Kris Johnson said:


> What about Nubian vaults? (sorry if this has been suggested before) They fit both criteria. A quick google or youtube search for Nubian vaults or (la voutte Nubian) will give you a lot of info on the technique.


I started with Nubian vaults 5 years ago 









And if you search vaults i built two small houses similar to the nubian method but with burned brick and not inclined.

But for (reason #2) pure beauty and strength i do Catalan Vaulting. I started small stuff which i have posted here. This one is a large room.









We are comfortable with catalan vaulting and are ready for bigger projects. It is more expensive though


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## CanCritter (Feb 9, 2010)

some of thos pics look like foundation settlement were roofs concerned..am surprised bricks pulled apart like that...woulda had some sorta lath on top concreted in..bottom line looks to be some settlement and lath woulda kept it from completely failing but would failed
enshure any waters drained away from foundation or sppts


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## Kris Johnson (Dec 20, 2013)

Your work is beautiful work no matter what the technique!


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## Fundi (Jan 5, 2009)

CanCritter said:


> some of thos pics look like foundation settlement were roofs concerned..am surprised bricks pulled apart like that...woulda had some sorta lath on top concreted in..bottom line looks to be some settlement and lath woulda kept it from completely failing but would failed
> enshure any waters drained away from foundation or sppts


Ancient thread. It is on second floor on top of ring beam and column. It was substandard brick failed under heavy load. I successfully rebuilt this and another and in the forum .

couldn't put lathe on top while building.


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## stonecutter (May 13, 2010)

Lath and concrete would have done nothing to stop the arch from pulling apart anyway.


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