Porosity problems of new unpainted Sheera roof - silicone spray?

[cliveshep]

This is a bit long but please humour an old fool!

 

I once bought an ex-council house in Cambridgeshire in the UK that was built of sand-lime bricks. These are bricks of extremely high porosity and although soft are quite dense. For that reason PM's "like wot I was" would always specify their use under-ground only, i.e in foundation brickwork where the ability so suck up a pint of water was irrelevant. Needless to say they were a cheap brick. 

 

Getting to the point - bear with me!

 

These house looked fine until it rained, rain with wind behind it simply waterlogged the bricks and when the Council workmen who failed to note that my house was in private hands obligingly drilled holes all round it and pumped insulation into it's cavity it formed a perfect bridge to bring water into the building via window heads etc - there being clearly no cavity trays either.

 

I found a silicone liquid, looked like white spirit, smelt like it too, that I applied with a garden sprayer, liberally soaking these porous bricks. Result - 100% success, the bricks did not go dark grey from white in the rain, the water simply rolled off.

 

Now to the point of this rambling - I am building a cheap (I'm on a limited pension on a continually worsening exchange rate - thanks Theresa!) extension as additional room for outside recreation space and "dirty" (meaning for smelly foods) kitchen. I've done the roof using engineering skills gained in a lifetime of design in the UK, which means probably using 25% of the steel normally used in Thai construction, no wall plate but cleats chem-fix bolted into the walls, steel box sections minimum size that allow old fatso to walk over them and the cheapest unpainted grey Sheera corrugated roof sheets. I've done all the work myself, cutting, welding, Tek-screwing, and the roof is on, plus gutter and downpipe and walls under also Sheera.  Here's the fun bit - the sheets soak up water and leak now it is raining, presumably because being only 26 baht each and unpainted they really are the bottom of the range. Silly me for expecting Thai roof sheets to keep out the rain!

 

So -  you all know what I'm going to ask don't you?

 

Please oh please tell me a name and place around Bangkok where I can buy some silicone proofing liquid! A product name would be good, you have no idea the confusion engendered when my wife translates what I want for the Thai Watsadu folk, if I cannot point to it I'm stuffed! Thanks all!

[Kwasaki]

1 hour ago, cliveshep said:

Sheera corrugated roof sheets. I've done all the work myself, cutting, welding, Tek-screwing, and the roof is on, plus gutter and downpipe and walls under also Sheera.  Here's the fun bit - the sheets soak up water and leak now it is raining, presumably because being only 26 baht each and unpainted they really are the bottom of the range.

That is not right steel roof sheets cannot be porous unless you have drilled lots of holes into them and have not sealed them with the correct roof fixing.

There's either a condensation build up on the underside of the roof sheet because you have no underlay membrane product installed or your cover roll lap is not sealed or if you have down roof sheet laps and the cover lap is to small or not sealed. 

[eyecatcher]

He didnt say they were steel sheets, they were shera cement based.

[carlyai]

Good work getting all that done.

Can you go to a Sherra place and get a pamphlet for the sheets and check if they are roofing sheets and the correct insulation method and waterproof paint recommended?

I know that doesn't answer your question, but roof coatings I've seen tend to not last too long in the heat in Thailand. (I haven't seen that many.)The guy behind us in Pattaya had roof leaks and was continually repainting the roof with that black tarry stuff.

If someone can't help you here find the right stuff, you could try that foam insulation under roof spray.



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[Snow Leopard]

I am not really sure on a coating for Sheera that would remain waterproof for any length of time. I don't know if this would work for you or at all. Would installing clear corrugated plastic sheets over the Shera help? It might solve years of continuous painting as well.   

[Pogust]

When I bought the shera roof (painted) I also ordered a small can of touch up paint. There is original roof paint avaiable. It's water based. But I think it's difficult to paint up between the overlaps. Should paint before fitting them.

[carlyai]

Hi Pogust, you seem to know what you're doing but some things I don't understand : you said the sheets were unpainted, but now it seems like they are painted.

I have bought Sherra products (not roof sheets) before and the pamphlets and material were of good quality. Are the roof sheets from Sherra or like Sherra?

I can't see Sherra making a painted or unpainted roof sheet that is porous and lets the water thru...what's the point?

 

You got a pic of the roof? Not just for me but for other people who have more knowledge than me. [emoji3]

 

Sorry: Shera not Sherra.

 

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[Andrew Dwyer]

Hi Pogust, you seem to know what you're doing but some things I don't understand : you said the sheets were unpainted, but now it seems like they are painted.
I have bought Sherra products (not roof sheets) before and the pamphlets and material were of good quality. Are the roof sheets from Sherra or like Sherra?
I can't see Sherra making a painted or unpainted roof sheet that is porous and lets the water thru...what's the point?
 
You got a pic of the roof? Not just for me but for other people who have more knowledge than me. [emoji3]
 
Sorry: Shera not Sherra.
 
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I think you are confusing Pogust with the OP .

The op said he bought unpainted .

[Fruit Trader]

If its Shera roof it should not leak through porosity and if it does call them for support.

 

Otherwise Bosny brand Thailand have a silicon liquid for porous surfaces.

 

Google Bosny Silicone Water Repellent

[carlyai]

'I think you are confusing Pogust with the OP .'
Yes, sorry [emoji21]

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[mogandave]

How steep is the roof?

[cliveshep]

Roof is probably 15 degrees pitch - but the issue is not one of pitch but porosity. Have you seen the price of some silicone impregnation liquids on this country? It would be cheaper to bribe Chan-Ocha to flee to Dubai! I found some in Thai Watsadu yesterday while buying screws and gap filler - frightening! Made by TOA a 2.5 litre can was over 1000 baht.

 

I only have 25m2 to flood impregnate but 2.5 litre won't go far even if I spray it and it really has to be "flood-coated" to soak in.

 

I emailed Bosny - so far they have declined to answer. 

 

As an aside, my wife said that when she was young (not that she is old now being less than half my age) her family home had a Sheera roof that actually dripped through in heavy rain. Looks like Sheera have questions to answer but I won't bother - I have not found anyone out in this part of the globe who stand by their products - caveat emptor seems to be a warning to heed here.

[canopy]

As already suggested, contact them and have a rep come out to look at the problem.

 

Another thing you can do is post a picture so people can see what you are talking about.

 

[kamalabob2]

Exactly which series of Shera roofing tiles did you install?  https://www.shera.com/th-en/icorner/view/161   I have observed improper "pitch" on a house plan being a valid reason a store would not sell a particular roof tile. In some roof brochures in Thailand the pitch or slope "minimum" is printed on the catalog for specific styles and lengths of fiber cement roof tiles.  I have found Shera a reputable company that will stand by products if the dealer had paperwork showing the sales date and had the influence to get the local representative to inspect the damage.  Improper installation, wrong screws, insufficient pitch all contribute to problems.  I've observed folks skip those pesky "dry tex" membranes on the ridge sections of a roof and wonder why they had leaks. The Op can easily find inexpensive Bosny Products at most any builders Merchant store. Dr. Fixit is a budget brand of building materials which make products in Thailand to solve leaks. The MD of Dr. Fixit attended College in Texas and is easy to communicate with.  http://www.bosny.com/construction.html   The OP should not give up on reputable manufacturers making a real effort to solve customer problems. The skill set of the actual worker who sometimes do not read instructions can make a difference in claims being paid. 

[mogandave]

I can’t imaging why anyone would buy roof panels, find out they leak, and rather just taking them back would spend additional time and money trying to fix the leaks.

[mogandave]

Exactly which series of Shera roofing tiles did you install?  https://www.shera.com/th-en/icorner/view/161   I have observed improper "pitch" on a house plan being a valid reason a store would not sell a particular roof tile. In some roof brochures in Thailand the pitch or slope "minimum" is printed on the catalog for specific styles and lengths of fiber cement roof tiles.  I have found Shera a reputable company that will stand by products if the dealer had paperwork showing the sales date and had the influence to get the local representative to inspect the damage.  Improper installation, wrong screws, insufficient pitch all contribute to problems.  I've observed folks skip those pesky "dry tex" membranes on the ridge sections of a roof and wonder why they had leaks. The Op can easily find inexpensive Bosny Products at most any builders Merchant store. Dr. Fixit is a budget brand of building materials which make products in Thailand to solve leaks. The MD of Dr. Fixit attended College in Texas and is easy to communicate with.  http://www.bosny.com/construction.html   The OP should not give up on reputable manufacturers making a real effort to solve customer problems. The skill set of the actual worker who sometimes do not read instructions can make a difference in claims being paid. 

Hey Bob, the Bosny products always seem cheap, how do you think the quality compares to the “better” name products?

[cliveshep]

4 hours ago, mogandave said:

I can’t imaging why anyone would buy roof panels, find out they leak, and rather just taking them back would spend additional time and money trying to fix the leaks.

Possibly because the sheets were fixed in the dry season, the whole roof was completed and flashed so taking the sheets back would involve dismantling everything, scrapping the flashing, and later having a load of roof sheets with holes in and possibly other damage. That might be a good reason not to attempt to take them back huh?

 

I'm beginning to wonder if the sheets are in fact Sheera at all, Thai Watsadu refer to them as Sheera but there is no stamp on them. They are a plain grey cement fibre sheet 1.2m x 0,5m and I have them at alternate row spacing, so 2nd row starts with a half-sheet (cut up the slope) which puts the joints staggered row to row. Vertical lap is 150mm minimum.

 

Minimum slope is 10deg - industry norm, but reflecting the severity of monsoon rains here I have gone for a little more than that although there is no question of the slope being the issue, it is the sheets soaking through.