How to effectively seal a flat concrete roof?

[Kwasaki]

7 hours ago, Mark Nothing said:

I volunteered on two condo boards over the years and we unsuccessfully dealt with flat roof leaking problems using a multitude of remedies similar to your ideas, none of which worked.

 

The penthouse owners were constantly complaining about leaks and black ceilings.  Year after year we tried different solutions at big expense.  

 

Pooling occurred on the flat roof after each rain and concrete cracks developed and grew over the years.  During heavy rain season the water drain pipes were too small to handle the volume of water to drain down, which caused backup of water and the roof flooded and the water entered condos.

 

Your house design is very nice though.

 

 

In UK we use to erect over flat rooftops a metal frame giving it about 5 degree's and put a sheet metal roof.

[degrub]

When we placed equipment of any kind that would require routine maintenance or inspection on a flat composite  or concrete roof with welded elastomer sheet or coating based membrane, we installed structural steel supported grated walkways to keep feet and tools off of the membrane.  Without that, we expected to have to repair the membrane within 5 years of use. 

[Encid]

14 hours ago, d4dang said:

I have an Ozzie friend who did solars for yonks...he is here in Th if you need advice

Please PM me his contact details... I did start another topic about an off-grid system but am now leaning towards an on-grid system.

Any and all advice would be welcome. 

[Muhendis]

6 hours ago, degrub said:

When we placed equipment of any kind that would require routine maintenance or inspection on a flat composite  or concrete roof with welded elastomer sheet or coating based membrane, we installed structural steel supported grated walkways to keep feet and tools off of the membrane.  Without that, we expected to have to repair the membrane within 5 years of use. 

That's the right thing to do but notice the drawing in post #3. The membrane is actually buried below the sand and screed top coat.

This is why I mentioned to keep an eye on hole depth if mounting anything on the roof.

 

My solar is on a flat and leaky car port roof. It's leaky because my (village) builder had not a clue.

It's ok'ish now but I wish I had been around when it was done............

[Encid]

Thanks for all the responses everyone... they have certainly given me a lot to think about.

 

I am now considering a ground-mounted solar array instead of roof-mounted, so no penetrations or damage will happen to the roof membrane (if we go with an RC roof as designed).

 

After chatting with our builder, we are also considering an alternative roof too... one that keeps the same appearance or profile from all sides at grade level up to 3m high, but will actually be a sloping Bluescope steel roof behind a concrete facade.

 

An early estimate gives us an overall 20% cost saving (based on reduced rebar steel in the roof and supporting columns) as well as an improved construction schedule.

 

More to come... 

[wangotango]

On 2/17/2023 at 12:34 PM, HighPriority said:

This is one eg of a sheet membrane system:

https://ardexaustralia.com/product/ardex-wpm-1000/

 

This is an eg of a liquid applied membrane system:

https://ardexaustralia.com/product/ardex-wpm-908/

 

The entire Ardex roof and deck waterproofing range can be found here:

https://ardexaustralia.com/products_category/waterproofing-roofing-membranes/

 

Ardex are a premium company, good products but they make you pay !

 

I've used the liquid applied membrane once, about 20 years ago but I've never used the sheet style membranes. I found the liquid applied product was difficult to apply neatly in the heat in Darwin Australia.

The sheet style membranes seem to have become the "go to" product for commercial projects from what I can gather.

The skillset and experience of the applicators should be your guide  in my opinion...

 

PS I'm surprised that you're only getting 50mm outlets to drain the roofs, I can see theres multiple of them but personally I'd be looking at more like 100mm, will take more volume and be more resistant to blocking with leaves etc.

100 mm pipes for sure. TIT

[Elkski]

Just found a great website that deals with the complexities of flashing for brick structures.  Jump to fig 59-61.   The top of your roof walls can't be just left uncovered.  The flashing starts here.  Bricks mortar assemblies are permeable. 

[Elkski]

On 2/20/2023 at 12:11 AM, Encid said:

Thanks for all the responses everyone... they have certainly given me a lot to think about.

 

I am now considering a ground-mounted solar array instead of roof-mounted, so no penetrations or damage will happen to the roof membrane (if we go with an RC roof as designed).

 

After chatting with our builder, we are also considering an alternative roof too... one that keeps the same appearance or profile from all sides at grade level up to 3m high, but will actually be a sloping Bluescope steel roof behind a concrete facade.

 

An early estimate gives us an overall 20% cost saving (based on reduced rebar steel in the roof and supporting columns) as well as an improved construction schedule.

 

More to come... 

I Iike the hidden metal roof idea. I'm picturing 3 sides of parapet facade with an open sloping drainage plane.   Maybe no drain pipes encased, better water collection, solar panel mounting.  Will have that rain sound but proper insulation should help that. 

[Encid]

On 2/26/2023 at 9:15 PM, Elkski said:

Just found a great website that deals with the complexities of flashing for brick structures.  Jump to fig 59-61.   The top of your roof walls can't be just left uncovered.  The flashing starts here.  Bricks mortar assemblies are permeable. 

Can you please provide a link to that website?

[Yellowtail]

It is worth noting that virtually all the shop houses in Thailand (of which there are many) have flat concrete roofs. 

 

 

 

[djtheoz]

Been reading this topic with much interest as I'm planning to extend our kitchen space on ground floor with its ceiling to become a roof terrace, accessed via the second floor. 

Don't see much bitumen-like solutions available here up North, nor membranes, to seal the terrace properly.  

Any thoughts here on (several layers) of TOA 201 acrylic roof sealer, applied directly on the top deck ?

A top deck surface of smart/cement boards, or solid concrete deck?

 

Seems to be stay flexible, resistant to high temperature and water tight for at least a few years (maintenance required, OK) ,  not very expensive and even available in different colors. 

 

https://www.toagroup.com/en/products/construction-chemicals/water-proofing/32/toa-201-roofseal
 

Serious option, or no way? 

  

[Yellowtail]

11 minutes ago, djtheoz said:

Been reading this topic with much interest as I'm planning to extend our kitchen space on ground floor with its ceiling to become a roof terrace, accessed via the second floor. 

Don't see much bitumen-like solutions available here up North, nor membranes, to seal the terrace properly.  

Any thoughts here on (several layers) of TOA 201 acrylic roof sealer, applied directly on the top deck ?

A top deck surface of smart/cement boards, or solid concrete deck?

 

Seems to be stay flexible, resistant to high temperature and water tight for at least a few years (maintenance required, OK) ,  not very expensive and even available in different colors. 

 

https://www.toagroup.com/en/products/construction-chemicals/water-proofing/32/toa-201-roofseal
 

Serious option, or no way? 

  

You want to extend the kitchen ceiling out to be used as a terrace for the second floor, is that correct? 

 

 

[djtheoz]

Yes...so basically a 4 x 4 x 4 m cube connected to a 2-floor building , inside as kitchen extension on ground floor, on top as terrace for the second floor. 

The roof of the main building overhangs about a meter from the facade/wall , and can not be extended to also cover the terrace.  
So the terrace needs to drain all rain water coming on it, similar to TS's flat roofed house.  
Difference is limited hours direct sunlight on the terrace (shadow side of the house). 

Considering to create a 'warm roof' construction with (smart board +insulation+ smart board) and seal it with the TOA 201 as roof covering in the picture below.

 

 

 

 

[Yellowtail]

Existing is all concrete, yes? If so, do you own or rent?

Renting I'd do it on the cheap "freestanding" with steel frame & smartboard walls and roof. 

Owning I'd drive piles and pour concrete,

[djtheoz]

7 minutes ago, Yellowtail said:

Existing is all concrete, yes? If so, do you own or rent?

Renting I'd do it on the cheap "freestanding" with steel frame & smartboard walls and roof. 

Owning I'd drive piles and pour concrete,

Thanks for your replies. 
Yes, we own the house. See picture. Sorry didn't make proper drawings yet to get an idea. 

The extension will come where the wheelbarrow is; 

Concrete frame of columns and beams, filled with red brick walls, as also is the existing building.

 

Looking for a easier and lighter alternative to a solid concrete slab on top.

There is these pre-fab concrete panels of ~60 x 400 cm I have seen the Thai using for flooring on top of concrete frames but can't reach it with a crane to lift them up high.
Hence the thought for a solution with smart boards with TOA 201.  

 

 


 

[Yellowtail]

4 minutes ago, djtheoz said:

Thanks for your replies. 
Yes, we own the house. See picture. Sorry didn't make proper drawings yet to get an idea. 

The extension will come where the wheelbarrow is; 

Concrete frame of columns and beams, filled with red brick walls, as also is the existing building.

 

Looking for a easier and lighter alternative to a solid concrete slab on top.

There is these pre-fab concrete panels of ~60 x 400 cm I have seen the Thai using for flooring on top of concrete frames but can't reach it with a crane to lift them up high.
Hence the thought for a solution with smart boards with TOA 201.  

 

 


 

Nice house! I'd look at the SCG (or similar) cement board flooring. 

 

If you have an SCG Home Store (they are everywhere) you might go down and talk to them, they can reccomend what to seal it with. 

 

I would use two layers and stagger the sheets such that the seams do not line up. 

 

 

[djtheoz]

22 minutes ago, Yellowtail said:

Nice house! I'd look at the SCG (or similar) cement board flooring. 

 

If you have an SCG Home Store (they are everywhere) you might go down and talk to them, they can reccomend what to seal it with. 

 

I would use two layers and stagger the sheets such that the seams do not line up. 

 

 

Thank you! Yes.. for sure a nice house.. with its charming never ending time consuming surprises  . 

Thanks for the tips! 
 
 

[Yellowtail]

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