11 ms·

Using a wicking rope to drain standing water on a flat roof (2024)

8 points by surprisetalk 1y ago

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Suppafly 1y ago
Good idea but shouldn't be necessary if the roof was done correctly.
- brudgers 1y ago
  Even more importantly, over time a sagging roof that holds water will sag more due to the weight of the water and being a "universal solvent" standing water degrades most materials. At best, you will probably get leaks. At worst, catastrophic [1] structural failure. On the other hand, reroofing can be relatively expensive [2] and disruptive and rope is cheap and everyone has their own risk tolerance and budget. [1] "catastrophic" in the engineering sense of material failures. [2] Particularly fixing a fundamentally flawed design. And standing water is a symptom of a fundamentally flawed design.
brudgers 1y ago
I asked the contractor if there was anything that could be done to prevent the standing water. He said it’s a common occurrence in the drain area and not a problem. Proper placement of the scupper prevents standing water. Low slope roofs with parapets require two drainage paths. A primary that is the lowest point and an overflow which sits above the lowest point. The purpose of the primary is draining all the water. The secondary has two purposes: 1. Drain water if the primary drain is clogged without exceeding the live load of the roof structure. 2. Alert the building owner that the primary drain is clogged. For example by dumping water out a visible scupper on the facade or in the case of internal secondaries by triggering an alarm in the building's management system. Standing water on a new roof is a symptom of improper design. Roofs are a place where it makes more sense to pay for architectural services because nobody ever gladly exchanged roof leaks for cost savings. And that roof is going to leak. TPO, properly installed can make a fine roof. But standing water will void any manufacturer's warranty because the roof is not properly installed. Coal-tar pitch is the only roof that can reliably resist standing water...and you won't save money installing coal-tar pitch, it's carcinogenic and a specialty trade. Finally, if you really want a reliable roof pay for a twenty year no-dollar-limit bond. The bonding company will come out and closely inspect everything before issuing the bond...and the contractor doesn't get retainage...so yeah you want a good contract, too. I'm sure the Redditor felt clever with all the money they saved. But if you are sitting at the table with contractors, to near statistical certainty you are the dumb money.

8 points by surprisetalk 1y ago

deleted 1y ago

[deleted]

deleted 1y ago

[deleted]

Suppafly 1y ago

Good idea but shouldn't be necessary if the roof was done correctly.

brudgers 1y ago
Even more importantly, over time a sagging roof that holds water will sag more due to the weight of the water and being a "universal solvent" standing water degrades most materials. At best, you will probably get leaks. At worst, catastrophic [1] structural failure. On the other hand, reroofing can be relatively expensive [2] and disruptive and rope is cheap and everyone has their own risk tolerance and budget. [1] "catastrophic" in the engineering sense of material failures. [2] Particularly fixing a fundamentally flawed design. And standing water is a symptom of a fundamentally flawed design.

brudgers 1y ago

I asked the contractor if there was anything that could be done to prevent the standing water. He said it’s a common occurrence in the drain area and not a problem. Proper placement of the scupper prevents standing water. Low slope roofs with parapets require two drainage paths. A primary that is the lowest point and an overflow which sits above the lowest point. The purpose of the primary is draining all the water. The secondary has two purposes: 1. Drain water if the primary drain is clogged without exceeding the live load of the roof structure. 2. Alert the building owner that the primary drain is clogged. For example by dumping water out a visible scupper on the facade or in the case of internal secondaries by triggering an alarm in the building's management system. Standing water on a new roof is a symptom of improper design. Roofs are a place where it makes more sense to pay for architectural services because nobody ever gladly exchanged roof leaks for cost savings. And that roof is going to leak. TPO, properly installed can make a fine roof. But standing water will void any manufacturer's warranty because the roof is not properly installed. Coal-tar pitch is the only roof that can reliably resist standing water...and you won't save money installing coal-tar pitch, it's carcinogenic and a specialty trade. Finally, if you really want a reliable roof pay for a twenty year no-dollar-limit bond. The bonding company will come out and closely inspect everything before issuing the bond...and the contractor doesn't get retainage...so yeah you want a good contract, too. I'm sure the Redditor felt clever with all the money they saved. But if you are sitting at the table with contractors, to near statistical certainty you are the dumb money.