Waterproofing a flat roof [Merged threads]

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Old 10-28-10, 03:56 AM
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Waterproofing a flat roof [Merged threads]

Hi all!

I live in a top floor appartment and the roof is a flat mosaic roof (aggregate mixed with concrete) I had waterproofing issues since I remember living in this house but lately the problem is getting worst.
The last waterproofing method that was used in the roof was tarmac sheets. I had problems with water ruining the roofs but at some point after a heavy rain most of roofs in the rooms in the appartment started dripping water!
After that we stripped the tarmac sheets, scraped the tarmac and removed a milimeter or so from the surface of the mosaic to restore the surface (not to leave any tarmac on it). After that we repaired all the water drains and after that we applied an epoxic resin-concrete mix that was supposed to be waterproof. It also improved the temperature in the appartment during the summer (it was boiling hot with the tarmac sheets). Note that the roof has some inclinations on it to drain the water to the water drains and it also has some expansion relief gaps.
Here is a picture of the roof at the moment:



This worked just fine for some months and I proceeded in painting the rooms that were damaged. But after some months (in spring) during a rain this happened:



You can see in this picture the damage done by the water.
Weird thing is that after that incident there was no water at all on the ceiling, even after heavy rains during the winter. But yesterday after a very heavy rain the room flooded. When I say flooded I mean that I putted some buckets to collect some of the water and they were emptied like 15 times during the night.
The prime suspects that I thought for the water infiltration at the moment are:
1. The expansion relief gaps, (the epoxic resin-conrete has cracked at some points, probably due to thermal expansion of the roof)
2. The chimneys.

But since the water ammount is quite a alot I also started to suspect that there might be some kind of pipe running through the roof that has cracked and is ruining the ceiling, (allthough I dont know why a water pipe would be installed in a roof slab).

Do you have any ideas of from where the water is comming through the roof and secondly of any reliable water proofing methods (I would prefer without tarmac sheets) in order to fix this problem effectively?
Many thanks
 
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Old 10-28-10, 02:07 PM
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Can you bring a hose or a pressure washer up there? Start testing on one side & go to the other. Have someone in the apartment during the test.
 
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Old 10-28-10, 02:59 PM
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I used to work for an outfit that had a waterproofing division [I seldom worked that part] They used an elastromeric/membrane system on flat roofs that worked surprisingly well. Basically an elastromeric coating was applied to a clean roof, then the membrane was applied with another coat of elastromeric rolled over top of it. I was skeptical but we put it on our warehouse roof and it held up great [no leaks] in the next 10 yrs that I worked there.

The elastromeric coating was white, I don't remember if it could be tinted.
 
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Old 10-29-10, 09:38 AM
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I did try to test the surface after the first water damage using a hose from the balcony. I left the hose on the expansion relief gap with the water running and left it there for about half an hour and there wasnt any water dripping from the roof below (there was water dripping in the roof below before applying the epoxic resin-concrete). I also tried a few other spots like the corners with the railings and so on but there wasnt any water dripping from the roof below. I havent tried with a pressure washer.
I had a look at some waterproofing companies and they have a few types of materials available.
One is the tarmac sheets which as they say they have to have a substancial thickness and weight per m2 in order to be effective and have strong weldings but since the tarmac sheets are very thick I suspect that they wont be able to be applied on the corners with the railings. They also make the rooms underneath very hot.
Another materials I saw were E.P.D.M, H.D.P.E and P.V.C membranes. I dont know anything about these materials or how they are applied (maybe with an elastomeric coating?) .
Apparently thickness in quite important for durabilty in these materials but wont it be bad if they are not applied on the surface of corners directly and have some air gaps underneath? Will they also be able to cover the peaks of the inclinations of the water drainage if they are very thick? Or will they get unstuck after a while?
 
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Old 10-29-10, 10:28 AM
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Corners & edges are the most vulnerable parts of the roof. I think you need to locate where the water is entering before you decide what to buy.
 
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Old 11-02-10, 06:56 AM
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Unhappy Choosing a contractor for a flat roof waterproofing

This is a follow up from a previous post that I made that can be found here:

http://forum.doityourself.com/roofin...flat-roof.html

The condition of the roof is as it seems on the pictures and described on the previous post.
I called a contractor to come over and check the condition of the roof but he did not say what the problem actually was or from where the water leak is but he gave us a quote of 6000euro for installing new tarmac sheets. Problem is that tarmac sheets make the flats very hot in the summer
A very interesting thing is that this contractor I never called, I called another contractor and these guys showed up, I verified that because the contractor that I called called me today and told me that he is not that contractor that came over and gave us the quote. The contractor that I called said he will be calling on Thursday.
Another contractor came over yesterday and gave us a quote of applying a "white stuff on the summer" (not sure what the white stuff is exactly) over the existing roof as it is.
I dont really trust the first contractor because I dont know where he actually found out that we need to fix the roof and I dont even know where they found me and the second contractors offer seems to me to be a bit of a botch thing.
Problem is that as time passes the roof keeps leaking and I cant even leave the appartment to go for a few days away!
What would you do? Do you think that I should call more contractors or should I just grab an offer quickly and fix the roof and "see how it goes"
Many thanks
 
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Old 11-02-10, 02:00 PM
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I'd wait and see what the 3rd contractor has to say. The 1st one may have been told about your leaks by someone you discussed your roofing problems with. I'm not familiar with the tarmac sheets - can they be painted white with an elastromeric coating?

The 2nd contractor sounds like he just plans to roll a coat of elastromeric over your roof. While it might be a short time fix I wouldn't trust that approach for a permanent fix. I'd only consider it if I was doing the labor and money was short.
 
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Old 11-02-10, 02:48 PM
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Tarmac sheets is basically that black stuff:



I am not really sure how they are called but they are a very fashionable solution here for waterproofing roofs. I know that they contain tarmac and that they come in rolls.
Basically that stuff apparently is a good solution for waterproofing the surface for about 10 years with good maintanance (or so they say) but they make the rooms very hot.
The first contractors didnt just show up, they actually called me on my mobile phone to arrange an appointment and they sent me today their offer which says:
"Tarmac sheets of 6kg per m2 weight with a elastomeric coating of white aggregate" (this is nonsense right? Elastomeric coating is not an aggregate isnt it? Nor that I heard of 6kg per m2 tarmac sheets either)
The second contractor apparently was also planning to apply a new cover of tarmac sheets. That contractor mainly spoke with the building administrator and since there is a bit of a communication issue here I am not exactly sure what the offer exactly was.
Both these contractors did not tell us of where exactly the problem was. (From where the leak is).
I will check with the third contractor and see what he says but at the moment I feel very very dissapointed with the situation.
 
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Old 11-02-10, 04:57 PM
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I wouldn't hire anyone to do anything other than to find the leaks.
 
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