I believe there are two ways to ensure a leak proof roof
1. Apply water proof compound coat, and then do surkhi (brickbats, sand, cement with water roof solution).
2. Apply water proof compound coat, and then lay some clay tiles.
Which would be better. I understand the second option would be more expensive (due to tile cost and laying cost).
Thanks
Roof waterproofing
Re: Roof waterproofing
As far as I know, we can do it in more simpler way:
1. Add a water-reducing chemical in the concrete, while adding water to the cement,sand and metal mixture. The reason this needs to be done is that, generally the masons increase the amount of water in the concrete mix so as to get the workability (in layman's terms it means the concrete should flow easily from the gamelas while pouring it on the slab). This additional water in the concrete is not good for the health of the concrete, but those masons and the guys at the mixer will not listen to you, if you ask them to reduce the water quantity. If you add this water-reducing chemical, then it automatically improves the workability even with the optimal amount of water required (please not that I am saying 'optimal' quantity, I am not advocating for reducing the water quantity in the mixture - I am only saying it should be 'optimal' - not more, not less, but the just the perfect quantity)
2. The day after the slab is laid, typically for the last roof of the building, we put a damp proof course. This does not require adding brickbats or tiles. Here you will be having a mixture of cement, sand and baby chips and add the water proofing chemical. Use of water-reducing chemical that I mentioned above, is also recommended here, apart from the water proofing chemical.
3.After completing step2, immediately you need to do a Kalai, which is nothing but finishing the mortar work with a mixture of cement and fine sand called as 'Kalai' in local lingo. This is done by creating an upward slope near the junction of slab and the parapet wall so that the water does not seep into the slab from the edges of the slab. If the parapet is not already built, which is generally the case, you can just have the first 1 or 2 courses of the brick wall laid, to finish this 'galtha' job (again local lingo for this task).
These 3 steps should take care of water proofing the roof. The alternatives that you have provided, as far as I know, only increase expenditure and are not as effective as the 3 suggested steps above.
I have given this gyan, being a civil engineer and having successfully done water proofing for all the buildings that I have built in the above manner. I have not had any complaints so far, by following this method.
1. Add a water-reducing chemical in the concrete, while adding water to the cement,sand and metal mixture. The reason this needs to be done is that, generally the masons increase the amount of water in the concrete mix so as to get the workability (in layman's terms it means the concrete should flow easily from the gamelas while pouring it on the slab). This additional water in the concrete is not good for the health of the concrete, but those masons and the guys at the mixer will not listen to you, if you ask them to reduce the water quantity. If you add this water-reducing chemical, then it automatically improves the workability even with the optimal amount of water required (please not that I am saying 'optimal' quantity, I am not advocating for reducing the water quantity in the mixture - I am only saying it should be 'optimal' - not more, not less, but the just the perfect quantity)
2. The day after the slab is laid, typically for the last roof of the building, we put a damp proof course. This does not require adding brickbats or tiles. Here you will be having a mixture of cement, sand and baby chips and add the water proofing chemical. Use of water-reducing chemical that I mentioned above, is also recommended here, apart from the water proofing chemical.
3.After completing step2, immediately you need to do a Kalai, which is nothing but finishing the mortar work with a mixture of cement and fine sand called as 'Kalai' in local lingo. This is done by creating an upward slope near the junction of slab and the parapet wall so that the water does not seep into the slab from the edges of the slab. If the parapet is not already built, which is generally the case, you can just have the first 1 or 2 courses of the brick wall laid, to finish this 'galtha' job (again local lingo for this task).
These 3 steps should take care of water proofing the roof. The alternatives that you have provided, as far as I know, only increase expenditure and are not as effective as the 3 suggested steps above.
I have given this gyan, being a civil engineer and having successfully done water proofing for all the buildings that I have built in the above manner. I have not had any complaints so far, by following this method.
Re: Roof waterproofing
Dear Civil88.
Unfortunately, my slab was cast around 3-4 months ago, and the 3 steps above was not done.
My father did the above steps while constructing his house over 20 years ago. He suggested the same to me. But my smart ass contractor said no one does that these days, it will not work, I have contructed 170 houses etc etc.
And talking to other people, no one seems to be doing what you mentioned above, though it seems to be tried and tested.
Now that I have not done the above, what is better? Water proof chemical course with Surki, or Water proof chemical course with Tiles.
Also, when I was inquiring with my contractor on doing the damp proof course the next day, his question was "how will the slab get cured if you put the DPC next day?". They build "pathis" and stagnate water on the slab for curing purpose. So if the DPC is done next day, the water will not go to slab for curing purpose. I did not press for the DPC next day since I did not have an answer to this. Any idea how I should have responded?
Unfortunately, my slab was cast around 3-4 months ago, and the 3 steps above was not done.
My father did the above steps while constructing his house over 20 years ago. He suggested the same to me. But my smart ass contractor said no one does that these days, it will not work, I have contructed 170 houses etc etc.
And talking to other people, no one seems to be doing what you mentioned above, though it seems to be tried and tested.
Now that I have not done the above, what is better? Water proof chemical course with Surki, or Water proof chemical course with Tiles.
Also, when I was inquiring with my contractor on doing the damp proof course the next day, his question was "how will the slab get cured if you put the DPC next day?". They build "pathis" and stagnate water on the slab for curing purpose. So if the DPC is done next day, the water will not go to slab for curing purpose. I did not press for the DPC next day since I did not have an answer to this. Any idea how I should have responded?
Re: Roof waterproofing
Hi Kpb,
The answer to your contractor's question is that pathis can be built on the DPC, the next day of laying DPC. And Curing can be continued in the same way of stocking water in the pathis.
Never mind, if you have not done the DPC immediately after the slab, it is not a problem, though it is most preferred way to do it.
Now you may use the Roofgaurd chemical from Armstrong company.(http://armstrongchemicals.com/) to carry out the water proofing.
If you want this to be executed by a professional, I have some contacts. You can PM me. His name is Krishna Kumar and operates from Ganga Nagar.
The answer to your contractor's question is that pathis can be built on the DPC, the next day of laying DPC. And Curing can be continued in the same way of stocking water in the pathis.
Never mind, if you have not done the DPC immediately after the slab, it is not a problem, though it is most preferred way to do it.
Now you may use the Roofgaurd chemical from Armstrong company.(http://armstrongchemicals.com/) to carry out the water proofing.
If you want this to be executed by a professional, I have some contacts. You can PM me. His name is Krishna Kumar and operates from Ganga Nagar.