Cable Stay Carport Roof And Missing Corners

[brahmburgers]

in Chiang Rai on non-titled property which I've had for over 10 years....

I don't know where the images are in relation to this text, so anyway....

There are 2 shots. The first shows an upper story being built (the ground floor is not visible, as it's below the retaining wall from this angle). Imagine a carport with no columns to negotiate. That's what I had in mind when designing this gable roof. 70% of the roof is being held up by two cable stays which are anchored to strong cement posts at the house (far side in the photo). The cable is 1 cm steel.

The 2nd photo shows one window (of two) which are set right in the corner of the house walls. This should drive Asians nuts, as all Asian builders know 'it's imperative to have strong columns in corners' Asians don't even like to see inter-linking blocks/bricks at corners. Well, we done did it another way. Am not sure yet whether to have the windows in two panes, with a silicon bead where they meet or ....I'll most likely make the windows one pane facing 45 degrees to the corner - though the sill will be a bit of a challenge, not too tough. I got a load of beautiful milled lumber from a tree which I cut down (was threatening another house), so we'll use that for doors and window sills and such.

[Crossy]

Interesting carport design, I like the idea of no columns to hit after an ale or two

I am no structural engineer but would worry about the weight of the roof materials on what appear to be very slender off-vertical stay towers, remember there's a lot of compression load here and the slightest bow in those towers will cause a huge bending moment and failure. How about cross-tieing the tops of the towers to the opposite side plus some diagonal bracing?

What about overall stiffness of the car port roof in a breeze? Remember Tacoma Narrows?

How about holding it down when a gust of wind gets in under it? Big area with only gravity to keep it in place.

[Rimmer]

Why ever did you not use Q Con blocks they are load bearing and can be lapped at the corners. From what I can see the blocks in the picture are not load bearing, are not lapped on the corners and do not have a re enforced concrete band tying the structure together at window sill height. The structure will most likely burst outward.

You have also used drain pipes as sow poons, so the building is not entirely devoid of support, did they vibrate the concrete down in them because if they did not there will be a lot of cavities and the drain pipes will collapse.

Tell me you are not going to put a C Pack tiles on the roof, not only is that small box section steel not strong enough but the weight of tiles will most likely collapse the entire structure under the weight. Even the 1meter cement sheets weigh a heck of a lot when you get a lot of them on a roof.

[khundon]

in Chiang Rai on non-titled property which I've had for over 10 years....

I don't know where the images are in relation to this text, so anyway....

There are 2 shots. The first shows an upper story being built (the ground floor is not visible, as it's below the retaining wall from this angle). Imagine a carport with no columns to negotiate. That's what I had in mind when designing this gable roof. 70% of the roof is being held up by two cable stays which are anchored to strong cement posts at the house (far side in the photo). The cable is 1 cm steel.

The 2nd photo shows one window (of two) which are set right in the corner of the house walls. This should drive Asians nuts, as all Asian builders know 'it's imperative to have strong columns in corners' Asians don't even like to see inter-linking blocks/bricks at corners. Well, we done did it another way. Am not sure yet whether to have the windows in two panes, with a silicon bead where they meet or ....I'll most likely make the windows one pane facing 45 degrees to the corner - though the sill will be a bit of a challenge, not too tough. I got a load of beautiful milled lumber from a tree which I cut down (was threatening another house), so we'll use that for doors and window sills and such.

I don't think you need to worry about hitting the cable supporting bars, as that roof is not going to stay up long enough for you to park a car under it.

The steel structure that you expect to support the tiles/cement sheets is way to light for the purpose, and that "cable stayed support system" on which you have so much faith, will buckle under the weight.

I assume that you will be fitting a suspended ceiling, that will almost double the weight you will be putting on the support structure. I think you had better get yourself some sky-hooks.

On cable stayed structures, normally, the cable goes from a fixed point on the bridge deck, over a VERTICAL concrete or steel column, which is put into compression and acts as a fulcrum, then back to a fixed point on the bridge deck. That is how the system gets the strength to hold up the given load. What you have there is nothing more than a big fishing pole and we all know what happens to those, when a big fish is on the hook.

If, by sheer luck, you get the roof on the car port to stay up, a good gust of wind under it will lift it up, because that steel structure is not rigid enough to resist the wind forces and when it comes down, it will do so on your car.

The round pipes even if they are filled with concrete are not large enough in cross section, even if they have re-bar cages inserted, also, they don't seem to be tied into the adjoining block work.

While it's not true that you always need a vertical support column at the corners, it is generally accepted that a horizontal concrete beam is installed above and below any window opening and all corner block work should be designed as load bearing and keyed into the adjoining wall by interlacing the blocks, or by using steel corner ties built into alternate block courses.

As your design stands, the slightest movement will cause vertical cracks in these areas and within a month, you will have more windows than walls.

Who designed this (I hesitate to call it a building) and who is doing the work. I would love to see the building from the other elevation, showing both floors.

Sorry, but If I was you, I would knock it down and ask for my money back.

[brahmburgers]

Thanks for the responses.

The roof covering will be metal roof sheeting with 1" stryrofoam glued underneath for insulation.

I'm the designer/builder. I could be wrong, but I think it will be standing firm in a year and ten years onward. The windows for sure. The carport likely.

[Rimmer]

I was always taught and any architect will tell you that when it comes to roofs weight is important but one has also to consider the lift and forces generated on the leeward side of a roof. Looking at your design I think you have an almost perfect aerofoil section to generate lots of lift, so maybe it's a good idea to anchor those corners to the ground as well as hanging them from above.

[trogers]

I would hang some 50kg cement bags at selected positions to do some load-deflection tests before spending hard cash on installation of roof cover.

[brahmburgers]

The finished roof just went through its first big test. Strong gusts of winds went through our neighborhood this afternoon, knocking over large trees and flattening neighbor's carport. The carport roof looks fine.

Below is photo, looking southeast

[brahmburgers]

I don't think you need to worry about hitting the cable supporting bars, as that roof is not going to stay up long enough for you to park a car under it.

The steel structure that you expect to support the tiles/cement sheets is way to light for the purpose, and that "cable stayed support system" on which you have so much faith, will buckle under the weight.

I assume that you will be fitting a suspended ceiling, that will almost double the weight you will be putting on the support structure. I think you had better get yourself some sky-hooks.

On cable stayed structures, normally, the cable goes from a fixed point on the bridge deck, over a VERTICAL concrete or steel column, which is put into compression and acts as a fulcrum, then back to a fixed point on the bridge deck. That is how the system gets the strength to hold up the given load. What you have there is nothing more than a big fishing pole and we all know what happens to those, when a big fish is on the hook.

If, by sheer luck, you get the roof on the car port to stay up, a good gust of wind under it will lift it up, because that steel structure is not rigid enough to resist the wind forces and when it comes down, it will do so on your car.

The round pipes even if they are filled with concrete are not large enough in cross section, even if they have re-bar cages inserted, also, they don't seem to be tied into the adjoining block work.

While it's not true that you always need a vertical support column at the corners, it is generally accepted that a horizontal concrete beam is installed above and below any window opening and all corner block work should be designed as load bearing and keyed into the adjoining wall by interlacing the blocks, or by using steel corner ties built into alternate block courses.

As your design stands, the slightest movement will cause vertical cracks in these areas and within a month, you will have more windows than walls.

Who designed this (I hesitate to call it a building) and who is doing the work. I would love to see the building from the other elevation, showing both floors.

Sorry, but If I was you, I would knock it down and ask for my money back.

Sorry, but you're wrong. You're welcome to come visit me in Chiang Rai, if you want to see some of my 'outside the box' construction methods. Definitely won't find my sorts of designs in your regular engineering manuals - but they're sound. ....and the corner windows (with no corner posts) are fine also, not the slightest problem. Below is photo which shows kitchen window. It's one of two in the house.

[maidu]

I don't think you need to worry about hitting the cable supporting bars, as that roof is not going to stay up long enough for you to park a car under it.

The steel structure that you expect to support the tiles/cement sheets is way to light for the purpose, and that "cable stayed support system" on which you have so much faith, will buckle under the weight.

If, by sheer luck, you get the roof on the car port to stay up, a good gust of wind under it will lift it up, because that steel structure is not rigid enough to resist the wind forces and when it comes down, it will do so on your car.

The round pipes even if they are filled with concrete are not large enough in cross section, even if they have re-bar cages inserted, also, they don't seem to be tied into the adjoining block work.

As your design stands, the slightest movement will cause vertical cracks in these areas and within a month, you will have more windows than walls.

Who designed this (I hesitate to call it a building) and who is doing the work. I would love to see the building from the other elevation, showing both floors.

Sorry, but If I was you, I would knock it down and ask for my money back.

Hi Khundon, my guess is you're a retired engineer. Probably a good thing that you retired, because younger more agile-minded engineers are needed for current and future challenges. You just sip your beer, and reminisce about the brownstone block buildings you helped build in the 1960's, and let the younger creative engineers take over, no problem. By the way, I've had a close up look at the house that Brahmburgers designed and built. It's gone through 2 monsoon seasons, and not a hint of problems in the two items mentioned. The two corner windows are doing fine, with curved plexiglass instead of glass, and not a crack or sag to be seen anywhere near them. You should come by Chiang Rai and see them, they're quite cool.

And the carport roof with no corner posts, which Khundon asserts; ".....is not going to stay up long enough for you to park a car under it. " has weathered months of occasional high winds and storms (which knocked down large trees in neighborhood), and nary a problem - it's still there, as sound as when it was first built. I'll get recent photos if you want to see 'em.

[David006]

Interesting design..goodonya for sticking to your guns...free thinking innovation helps the world go round...

...remember people saying cellular phones were a wast of time!

many people would have said that positive air pressure stadium roofs, "sail" type roofing etc, cantilevered roofs etc would never stand up

maybe some of the world finest architecture would never have been built if they had listened to naysayers..

[Naam]

Thanks for the responses.

The roof covering will be metal roof sheeting with 1" stryrofoam glued underneath for insulation.

I'm the designer/builder. I could be wrong, but I think it will be standing firm in a year and ten years onward. The windows for sure. The carport likely.

there can't be any doubt that you are an expert and that is enhanced by your idea of "insulation" you are planning to add to the roof

[maidu]

Thanks for the responses.

The roof covering will be metal roof sheeting with 1" stryrofoam glued underneath for insulation.

I'm the designer/builder. I could be wrong, but I think it will be standing firm in a year and ten years onward. The windows for sure. The carport likely.

there can't be any doubt that you are an expert and that is enhanced by your idea of "insulation" you are planning to add to the roof

Are you habitually snide? If you have better ideas for insulating roofs, let us know. I also got in the habit of gluing styfofoam panels under exposed roof panels. Here are some of the advantages, beside the obvious advantages of insulating against heat and sound:

>>> It's cheap. Sure there are costlier options, like having styrofoam sprayed, yet that could be hundreds of thousands of baht.

>>> for an open beam ceiling, it looks ok, if one doesn't mind white color. p.s. don't try painting it with oil base or touch up with white spray paint, as it will melt.

One disadvantage to false ceilings is they can harbor reptiles, dirt and insects. As much as you think you're keeping them out, they'll find a way to invade false ceiling spaces after awhile. At least with open beam ceilings, you can more readily see what's up there. Admittedly, the styrofoam has some drawbacks: the glue needs to stick for years, despite temperature changes, and once in awhile a large gecko might get in the space between the roof tiles and the styrofoam.

[Crossy]

I also got in the habit of gluing styrofoam panels under exposed roof panels.

Styrofoam or polystyrene foam is incredibly inflammable and emits highly toxic black smoke, it also tends do drip whilst it burns, whilst it is very effective it is most definitely NOT suitable for use as thermal insulation.

Do note that there are foam blocks that are intended as insulation which are fire inhibited and will be marked as such, unless you are using these you are placing yourself and your family at unacceptable risk.

The spray on foams are usually polyurethane based.

[maidu]

good call (and reminder) about styrofoam being inflammable. Perhaps not as much as wood, but most houses in Thailand are wood, either inside or outside or both.

One consolation re; the houses I've built with styrofoam insulation is they're all masonry, with the exception of door and window frames/sills. I still acknowledge the potential danger of styrofoam touched by flame, so thanks for the heads up on that.

[Spoonman]

Novel idea with the car port, should have just used corner posts as they would have been in the way just as much as your fishing poles and it would look square rather than the off kilter lean it looks to have now.

[Pacificperson]

The other problem with Styrofoam is that termites move through it like fish in water. Once they have established a nest in it, the only way to get rid of them is to bait them out.

[maidu]

Novel idea with the car port, should have just used corner posts as they would have been in the way just as much as your fishing poles and it would look square rather than the off kilter lean it looks to have now.

I'll get a recent photo of it. It's not off kilter, and no lean at all, after 22 months - some of those times with winds toppling nearby trees and blowing down branches 2 feet thick, the odd-looking carport roof took it all in stride.

[Spoonman]

Novel idea with the car port, should have just used corner posts as they would have been in the way just as much as your fishing poles and it would look square rather than the off kilter lean it looks to have now.

I'll get a recent photo of it. It's not off kilter, and no lean at all, after 22 months - some of those times with winds toppling nearby trees and blowing down branches 2 feet thick, the odd-looking carport roof took it all in stride.

How tall was the tree to have 2ft thick branches ?

Edited August 21, 2011 by Crossy
flame removed