Help with Building Assignment!!!!

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  #1  
Old 11-19-10, 04:06 AM
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Talking Help with Building Assignment!!!!

Hi, My name is Matthew and I'm currently completing my building and construction course at tafe. I have recently been handed a assignment involving me to evaluate a concrete roof.

I have to expain the possible reasons for the water damage and then expain some possible solutions available in rectifying the roof area.

My question is would anyone be willing to give me any advice? More the better

Below is the The question and the photo on the Concrete roof I will have to comment on.


 
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  #2  
Old 11-19-10, 07:26 PM
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This situation seems familiar to me as I am having this problem at the moment.

Some topics I would examine for those questions are:

Q1.
-How porous the concrete surface is.
-The waterproofing coating was less elastic as needed (you can calculate thermal expansion of a concrete roof) with result cracks to appear where water can infiltrate.
-If the waterproofing coating was applyed properly.
-Water might be entering the concrete slab through the water drains if damaged.
-Water is moving throughout the concrete slab according to inclination etc.
-Testing with a water hose could show from where the water is leaking but that would deliberately cause water damage to the ceiling under, if the ceilings are allready badly damaged then that might be useful.
-Maybe the contact areas between concrete and chimneys and railings have gaps that allow water to infiltrate on the concrete.
-The water damage on the railings (rust) is probably caused by exposure of the material to the elements.
-An ultrasonic testing device could be used to check for cracks in concrete structures.


Q2.
i.
For a long term solution the material needed has to be able to withstand the weather conditions and mechanical stresses that would be applied to it. For example the materials would need, good uv-resistance, adequate thermal resistance for the temperatures on the area, adequate elasticity over the years for the thermal expansions. Also the water infiltration resistance in pressure units could be checked if adequate for the water pressure applied. Since this will be a walkable surface materials with not good performace under traffic load should be avoided.
Possible solutions are:
1. An application of a waterproofing coating with the desired characteristics.
(elastomeric, resin, concrete based, etc there are loads available)
2. An application of a waterproofing membrane with the desired characteristics.
(not asphalt membranes as they are not walkable)
3. A combination of the above.
4. The construction of a tile? roof over the existing structure (if structuraly possible and allowed by regulations).
5. Maybe the application of tiles on the surface but thats not very common...
6. The construction of a roof-garden?
You can also consider enviromental impact of the materials used and safety in application. Also ease of workability to ensure the performance characteristics of the material.

ii.
For the rectification procedure I would think:
1. Removing and disposal of all damaged material from the roof.
2. Repair the water drains.
3. Do some testing to locate the leak.
4. Prepare the surface for the application of the waterproofing method.
5. Apply the water proofing method.
6. See if that solved the problem and then proceed with repairing the damage in the inside of the building.
You might also want to consider the correct time of the year to do the works, administrative procedures as Building Managment Services and also an economic-technical analysis and maybe a flow chart for the works such as Critical Path Method?

Further testing could be to wait to see if that solved the problem or throw some water on the roof to check if there are still water leaks.
Another testing could take place some time after the application. Also testing of the water drains for blockage could be performed.

Equipment used for the waterproofing application would depend on the solution selected probably. For example if the materials need to be mixed, torch-applied, torch-merged, rolled with a roller, applied with a brush etc. I would also think about safety equipment if needed such as gloves, respirators, masks, protective clothing etc. For the drains, drills and other electric tools might be needed also concrete mixing equipment, possibly heat guns for merging the drain parts etc.

The correct methods would be the ones that provide the desired characteristics of the solution. For example the desired performance, enviromental concerns, cost concerns, least works duration, least hazards involved, etc. As the concern here is the surface to be trafficable I would consider the most suitable of all the methods provided that would provide a trafficable surface.

Good luck
 

Last edited by Volnix; 11-19-10 at 07:54 PM.
  #3  
Old 11-20-10, 06:07 PM
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Thank you very much! that is great help

I have the second question complete now and but I'm still having trouble with question 1. So far i have said:

Vent Stack: If the vent stacks have not been patched up completely and the waterproof membrane was not painted on correctly around the penetration it could leak water when it rains and therefore allow water to penetrate into the slab and damage the ceiling.

Handrail posts: The handrail post show rust stains around the base which means the water has penetrated the slab threw the holes. This could then lead to concrete cancer and could also damage the ceiling underneath the slab.

Cracks in the membrane: The cracks in the membrane have only been patched by using a paint-on system. This system is very temporary and does not allow for the concrete to stretch. If not fixed the cracks will reappear and allow water penetration. The cracks will then become bigger and bigger and before you know it you will be having to replace the whole concrete slab.

Flat concrete roof deck: The concrete roof deck is flat which will cause the water to b stored in certain places throughout the slab, in turn creating puddles of water and more pressure on the waterproof system put in place.

Water drains off flat roof edge: The water will drain straight off the roof edge then come back underneath the slab and hit the ceiling. You will need to install a drip groove so it stops water from flowing back underneath the ceiling.

I need to elaborate more on this and use more technical terms but having trouble doing that. Any help would be greatly appreciated.
 
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Old 11-20-10, 09:19 PM
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Originally Posted by mattsilva View Post
Handrail posts: The handrail post show rust stains around the base which means the water has penetrated the slab threw the holes. This could then lead to concrete cancer and could also damage the ceiling underneath the slab.

The rust could just possibly be washed off on the concrete surface. A repair on the railings using metal plaster and a protective cover would protect the railings. Some might need to be replaced depending on the damage done by the oxidation.
If the reinforcement of the concrete slab is also starting to rust then that might cause some cracks on the slab due to internal pressure I think. An injection method with resins or some other method could be used to repair those.


Originally Posted by mattsilva View Post
Cracks in the membrane: The cracks in the membrane have only been patched by using a paint-on system. This system is very temporary and does not allow for the concrete to stretch. If not fixed the cracks will reappear and allow water penetration. The cracks will then become bigger and bigger and before you know it you will be having to replace the whole concrete slab.
The cracks wont get bigger I think, maybe a few fractions of a cm or so depending on the movement of the slab with temperature changes. They might get bigger if the coating starts chipping off from the sides of the crack. A solution whilst using a waterproofing coating is to place a mesh or a stick-on membrane and paint over with the coating. Any loose material from the cracks should be removed before application.
The coatings have an elastic factor that you could use to calculate the maximum elongation that they can reach. This according to theory could be used to calculate if the coating is elastic enough to follow the expansion of the concrete slab which you can also calculate. Fatigue could also be taken in mind since constant elongation could wear the system more quickly through cycle loads.
Its the first time I read about replacing a roof concrete slab


Originally Posted by mattsilva View Post
Flat concrete roof deck: The concrete roof deck is flat which will cause the water to b stored in certain places throughout the slab, in turn creating puddles of water and more pressure on the waterproof system put in place.
The roof is probably not completely flat, it might have some inclinations so the water will drain towards the water drains. The water will probably concentrate in some areas. The system used will probably have a resistance towards water pressure up to a certain value pressure. Some might allow water vapour to go through (some of the coatings I checked do) but water vapour goes up. The puddles formed might not wear the system more quickly then the uv rays of the sun or temperature but might be possible water leak spots when the system starts to wear.
 
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Old 11-21-10, 07:37 AM
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Good advice so far. Should get you going. Just a casual observation. Ditch the handrails. They only permeate the otherwise perfect seal. Safety on a roof like that could be achieved via tethers and a secured access. Vents should be sealed properly and not just tarred around. Edges need drip media to prevent capillary action. All these things, I believe you have addressed. One thing you didn't address and I feel is very important....why did the questioner mention it was near a "beach"? Salt water. Get into the detriments of salt air on all your components.
 
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