Weakspot in Thai house design, concrete flange above lower roof tiles

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thebears
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Weakspot in Thai house design, concrete flange above lower roof tiles

Post by thebears » Tue Dec 05, 2017 4:56 pm

Hi, I'm seeking an opinion on this from someone with construction expertise. I have had a problem with rats entering the space above the ceiling for several years. My property contains a number of places where there is a concrete flange, situated above a lower roof. I note that this is a very common style of building in local construction and mine is by no means unusual.

The problem is that rats are easily able to enter the roofspace, because of the inherent and perhaps unavoidable gaps between the roof tiles and the wall, which those concrete flanges do not cover. I do not know why they build in this way, as it is clearly a weak-point.

A construction worker has suggested that we concrete-in fully, the space between the flange and the tiles. I'd like to ask if this is a good practice and what would be right solution be? Thanks.
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NOKYAI
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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by NOKYAI » Tue Dec 05, 2017 10:06 pm

Would Sprayfoam roof insulation solve the problem (I’m not a builder)?
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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by brianks » Wed Dec 06, 2017 10:01 am

Sprayfoam should solve the problem along with giving you some other benefits.

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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by Nereus » Wed Dec 06, 2017 10:21 am

Just noticed this. First, do not use cement as it will probably crack the roof tiles due to different expansion rates and the difficulty of putting it there without any form work.

Spray foam, or crazy foam as it is sometimes called, would be a better option depending on how big an area is involved.

But mongrel rats will chew their way through wood to get where they want to go, so foam alone will not stop a determined rat. Some rolled up small mesh chicken wire stuffed in first will both hold the foam and also help stop them chewing any further.

No idea why it is built like that, but it appears to be the extended floor slab of a second story.
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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by thebears » Wed Dec 06, 2017 3:39 pm

Thanks very much for these replies, it's appreciated. Actually, this use of a concrete flange is a very common method in Thai houses, where there is a first-floor pitched roof adjacent to a wall, because local building methods and knowledge do not appear to incorporate the concept of lead flashing, between tiles and a wall to which they meet. No, the flange is not a floor slab. The three pictures attached all show the same concept. However, in some cases such as my home, there is an unusually large gap between the roof tile and the concrete flange.

In these attached pictures, it is only the blue bungalow which has a very small gap between the tile and the concrete. The other two properties have the concrete flange set directly onto the tile, which doesn't seem to be consistent with what you say about the concrete causing the tile to crack. In some properties the concrete is set onto the tile, while others - such as mine - have a gap. Both are very common though.

The weakness of course is that it is impossible, no matter how carefully a roof tile is cut, to make it fit perfectly against the adjoining wall. There will always be a small gap here and there.

If anyone else has solved this problem, I'd be really grateful for your direct experiences, thanks.
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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by hin » Thu Dec 07, 2017 2:00 am

Rats and mice can flatten their ribs and squeeze thru a very narrow opening. Easiest way might be to figure out how the rats are getting onto the roof. Are they climbing up those trees that are showing? If so, a narrow strip of sheet metal around the tree, like power companies put on their poles to prevent animals from climbing them. More laborious way would be to mix up some grout and trowel it into the gap over the tiles, which is the way our roof is done. But yours does seem to be large gap. Rats love to eat plastic foam so if they have already been in there it will not stop them.

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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by hin » Thu Dec 07, 2017 8:30 am

Also, they cannot walk upside down under a ceiling, like a gecko or insect, so would be difficult for them to get up past the eaves but they like to crawl thru pipes and tubes so can go up thru a downspout if your roof has gutters with downspouts that are not screened. Which is somtimes done to prevent bird nests from plugging them

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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by thebears » Fri Dec 08, 2017 10:50 pm

Thanks for the replies again. The rats are getting onto the lower roof areas mostly by going up the electric pole in the garden, then crossing towards the house via four electric power cables, from which they then need to drop down onto the roof. They even get into the main upper roof of the house. I know where the hole is and it's going to be blocked off also, though I don't know how they reach that height.

Perhaps there is something I can put around the power cables to prevent rats getting further along them. The trouble is, it's always so difficult to find competent people to do the work - most are just bodgers.

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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by hin » Sat Dec 09, 2017 10:04 pm

Get a narrow sheet of galvanized sheet metal, like used for roof flashing, to wrap around that power pole. They cannot climb past that. Tack it on if a wood pole or just cinch it on tightly with wire if its a concrete pole, but not so much wire to give them a foothold for easy climbing. If its a concrete pole don’t cover the holes that the power company crews use for climbing the pole.

A temporary remedy could be to get some of that thick syrupy sticky stuff that is used to catch mice and geckos etc. Wife spreads it on a piece of cardboard and when they walk across their feet become glued down into it. Available in markets in the pest control department. A bit of that on the pole should stop them but would need to be renewed occasionally.

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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by thebears » Mon Dec 11, 2017 2:01 am

Thanks for your ideas Hin, I'm going to fit the steel around the concrete pole as you suggest, but also continue with the filling-in of the flanges above the roof. The rats can sometimes jump from the trees also, so I want to prevent as many routes as possible.

My electricity pole in the garden is leaning over so much that if it continues, the rats will be able to walk along it anyway!

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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by VincentD » Mon Dec 11, 2017 12:50 pm

Look for rat trails - typically around a water pipe, you'll see a grey area to the left and right the whole length of it. I used this technique to block off access in my old company premises as the exterminator service just sent a couple of blokes once a week and all they did was set rat traps and some bait. They didn't even bother to come and clean up behind them when we had a casualty or two and had to do it ourselves. Waste of money imo.
I tried blocking access at home but they still got in. Eventually had to use rat bait and this was particularly difficult as the only access to the ceiling was through the downlights. They can scale both the inside and outside of drainpipes so I used wire mesh and toyed with making some inverted sheetmetal cones but as the rat bait did it's work I didn't have to.
Have been reasonably free of the b*ggers for a couple of months now. The scrabbling in the wee hours of the morning used to send me round the bend..
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Re: Weakspot in Thai house design, concrete flange above lower roof tiles

Post by thebears » Tue Dec 12, 2017 10:35 am

Thanks for the ideas and yes, I agree the scrabbling around in the roof is horrible. From what you describe, there were more ways in which these pests were able to enter your place. In my case, I do not have drainpipes or guttering. I can see the rats in the garden sometimes, usually at 5 p.m., then after a moment I'll hear one drop down inside the ceiling. We're going to block the concrete flanges and I'll report back with results, as it may be helpful to others.

It's interesting what you say about the pest control service. I used a local pest control company some years ago, to resolve an ant problem. When they visited, they insisted on getting me to sign a one-year contract for 7,000 Bt. It was a waste of money, since the results of the first visit resolved the ants completely. I noticed that they sprayed everywhere and everything. On each month's subsequent visit, they continued to 'drench' everything including leather furniture and possessions, even things in the middle of the room, without any thought for whether it was necessary. I'm sure they're aware that only one visit is necessary. Anyway, for others' benefit, it's possible to purchase the chemicals and a spray and do it yourself.

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