Minimum pitch (slope) for tarp roof for heavy rain runoff?

[Mother of Chaos]

Hi, all- we have a run with hardware cloth over the top for protection against predators. Half the run is covered with a heavy-duty tarp stretched flat over the HWC across the top. We’ve been having torrential downpours this summer. You see where this is going…

The rain doesn’t drain, and as a result, there are large and deep pools on the tarp. When we punch the tarp roof from below or sweep from above to drain the water, the chickens go into hysterics, and the humans don’t do much better.

We will be putting on a legitimate metal or polycarbonate roof this fall, but this can’t be done sooner. We’d like to do a pup tent-like support for the tarp in the interim. (Our tarp is big enough - it hangs over the sides now.)

What roof pitch/slope should we shoot for to allow decent drainage? 15°, 30°, etc.

 

[Ridgerunner]

I assume you are not worried about snow build-up. I don't know how much snow you might get, the roof needs to be strong enough to support the weight of the snow or ice.

You can get different opinions on how much slope you need on your permanent roof. Water will flow downhill as long as it slopes downhill all the way. If it is not perfectly level though it can pond. It needs to be supported enough to avoid ponding. If you could assure the roof is perfectly smooth with no variations you could probably get by with a slope of 1/2" rise per 12" length, some codes allow even less for "flat" roofs. This is just my opinion but I would want at least a 2" rise per 12" length for your metal or polycarbonate roof. It should drain and be flat enough to be comfortable for you to walk i\on. Others will call for more or less.

Your tarp will sag at any support. Unless you are going to build a pretty steep roof now I think you're just going to have to live with it. I've done that camping, put a tarp up to keep an area dry. When it rains I go out there and push from underneath to dump water before it builds up to be too heavy. That is a pain.

 

[Mother of Chaos]

I assume you are not worried about snow build-up. I don't know how much snow you might get, the roof needs to be strong enough to support the weight of the snow or ice.

You can get different opinions on how much slope you need on your permanent roof. Water will flow downhill as long as it slopes downhill all the way. If it is not perfectly level though it can pond. It needs to be supported enough to avoid ponding. If you could assure the roof is perfectly smooth with no variations you could probably get by with a slope of 1/2" rise per 12" length, some codes allow even less for "flat" roofs. This is just my opinion but I would want at least a 2" rise per 12" length for your metal or polycarbonate roof. It should drain and be flat enough to be comfortable for you to walk i\on. Others will call for more or less.

Your tarp will sag at any support. Unless you are going to build a pretty steep roof now I think you're just going to have to live with it. I've done that camping, put a tarp up to keep an area dry. When it rains I go out there and push from underneath to dump water before it builds up to be too heavy. That is a pain.

Thanks! We plan to have a 3/12 pitch to the corrugated roof when the time comes.

I agree that any slope for a tarp roof is better than none. It will be converted to a real roof before snow time. This question was actually asked for my husband. I appreciate your reply.

 

[McChooky]

If its covered in hw cloth and a tarp it needs guttering so it doesn't rot the foundation.A 1 inch drop every 12" is sufficient in most coops

 

[Mother of Chaos]

If its covered in hw cloth and a tarp it needs guttering so it doesn't rot the foundation.A 1 inch drop every 12" is sufficient in most coops

I was going with the manufacturer’s recommendation, but good to know! They do like to encourage a bit of overbuilding, I think.

And good point about the guttering. It’s on the list, with a rain barrel.

 

[McChooky]

I was going with the manufacturer’s recommendation, but good to know! They do like to encourage a bit of overbuilding, I think.

And good point about the guttering. It’s on the list, with a rain barrel.

'Temporary' uprights inside should help alleviate any problems.Good luck!