Load bearing veranda roof?

[bluesofa]

I want to put a tank on the roof of a veranda. The tank is 2 metres square.

The weight of the tank is less than 10kg. I have already established the weight of water in the tank will be no more than 80kg.

 

In the attached image the metal box section running left-right is 7cm x 3cm, the smaller box section above that (at right angles to the 7x3cm) is 3cm x 3cm. Both are spaced 1 metre centre-to-centre. The metal corrugated roof is immediately on top of that, where I want to put the tank.

 

What I want to know, is the roof sufficient to take the weight?

[Morakot]

Possibly not. Because of the angle and the way the "rafters" are secured with plate beam on top of the posts.

 

How exposed is this roof: i.e. is there strong wind occasionally?

[bluesofa]

11 minutes ago, Morakot said:

Possibly not. Because of the angel and they way the "rafters" are secured with plate beam on top of the posts.

 

How exposed is this roof: i.e. is there strong wind occasionally.?

Is this what you're referring to? Do you think it might tip over, or it just won't take the weight?

 

There is no problem with strong wind at all.

[VocalNeal]

Is it my math or yours? A 2m or 200cm square tank would be 40,000 sq cm and 80l of water is 80,000 cc so your "tank" is only 2 cm deep so more like a tray than a tank. 

 

Maybe the angel will help? 

[Morakot]

That's exactly what I mean. From this close up it looks secure enough not to tip over the beams. But because of the angle it can still push the post over time though.

 

I take it the rafters are about 50 to 60 cm apart and the beams are not completely rusty.

 

Will this be some kind of water heater?

[johng]

I would say it looks strong enough to take 90kgs of weight

Maybe have a few bracing struts welded between the rafters to stiffen against sideway swaying and wind force and immediately under the tank + dont have the tank slap bang in the middle if the roof position it either to the house wall or the support pillars.

 

 

[Morakot]

John, spot on!

 

In it's current state, I'm sure it will not collapse, but it will not be very secure either. A few simple additions, as suggested above should make it fit for purpose. May I also add a coat of anti-rust paint...

 

Good luck!

[VocalNeal]

I guess a good test would be to do a pull up and see if the roof will support one's weight?

[johng]

A good test but.....maybe get someone/s you dont like very much to the experiment while you look on at a safe distance

[bluesofa]

25 minutes ago, johng said:

I would say it looks strong enough to take 90kgs of weight

Maybe have a few bracing struts welded between the rafters to stiffen against sideway swaying and wind force and immediately under the tank + dont have the tank slap bang in the middle if the roof position it either to the house wall or the support pillars.
 

 

Yes, I had already though of positioning it over the house wall, thanks.

Also thanks for the suggestion abut painting the metalwork with anti-rust paint. Good idea.

 

I'm 70kg and have done a couple of pull-ups in the centre, between the house wall and the pillars, without any signs of strain (on the roof, more than can be said for myself).

Thanks for all the replies.

 

[Morakot]

19 minutes ago, VocalNeal said:

I guess a good test would be to do a pull up and see if the roof will support one's weight?

 

A "fail-safe" test?

 

 

The roof holds up with a person doing pull ups, but we still don't know how it will hold up with a 100KG installation on top of it over a long time with spells of rain and wind.

 

[Techno Viking]

must be a really shallow 2m x 2m tank to only hold 80 liters of water.

[Crossy]

56 minutes ago, Techno Viking said:

must be a really shallow 2m x 2m tank to only hold 80 liters of water.

Our OP needs to re-visit his calculations methinks. What are the actual dimensions of the tank?

 

[bluesofa]

1 hour ago, Crossy said:

Our OP needs to re-visit his calculations methinks. What are the actual dimensions of the tank?

 

OK, the full story:

It’s for a solar hot water panel, and it is actually a coiled length of plastic pipe, hence the 80kg/80L

 

The reason I didn’t explain what it was for, is that on another forum over a year ago, it just encouraged trolls to call me ‘a tree hugger’ and other abuse when I was asking about the same subject.

A case of once bitten twice shy. I hope it doesn’t start people trolling again, now I’ve explained the details.

 

[eyecatcher]

In that case the angle is ideal then......as long as its facing the right way for most of the day

[Crossy]

I don't recall a "tree-hugger" style post in any of these sub-forums.

 

Rest assured, any that appear will be removed as soon as we notice, use the Report button.

 

[Morakot]

Thanks @bluesofa for the clarification. All topics on sustainable energy DIY-projects are highly appreciated!

 

We would love to read more about your solar water heater system in detail. Whether designed or an off-the-shelve system... how you connected it... what you're your local circumstances.

[Morakot]

31 minutes ago, eyecatcher said:

In that case the angle is ideal then......as long as its facing the right way for most of the day

 

Might not be steep enough...

 

 

[eyecatcher]

5 minutes ago, Morakot said:

 

Might not be steep enough...

 

 

surely the steeper the angle, then it limits itself to catching very early or late sun when its low in the sky.

a shallower angle is going to catch 75% of the days sun, and if its flat, surely more??

 

isnt that logical or am i missing some solar technology knowledge?

[Morakot]

That's exactly what I thought too, EC!  But looking at most installations they seem to be at least 45 degrees.

 

 

https://metaefficient.com/news/solar-water-heaters-now-mandatory-in-hawaii.html

 

[Pogust]

If you have self-circulation (hot water rises) then 45° is needed to produce some flow in the pipes. Like the vacuum tube water heater in picture. With almost flat mounting you need a pump to circulate the water.

 

If you are worried about strength point weld another 7 x 3 cm under one or two beams and thus make it 14 x 3 totally.

[bluesofa]

Thanks for the positive comments.

 

Crossy, it wasn’t a TV sub-forum, but another forum completely, I am aware there are some occasional trolls on TV, but they seem to get dealt with.

 

Thailand latitude varies from 5 to 20 degrees north. As someone stated, the pitch of my roof is very close to the latitude for here in Thailand. Ideally the pitch of the solar collector panel needs increasing by about five degrees to line it up with the sun and ten degrees to get it pointing south. So not a lot of adjustment.

 

I have only just started with this, and anticipate a lot of testing and perhaps changing the design as it (hopefully) progresses.

 

So far I have wound some plastic pipe in a single row flat spiral, in order to do some initial testing on the ground, to see what results I get. I’m not rushing it at all, I want to try and get it right. Therefore my design is nothing like the images posted earlier.

 

I will update as and when I get some results, although it probably won’t be for a few weeks.

Thanks to everyone for the positive interest.

[VocalNeal]

13 hours ago, bluesofa said:

it is actually a coiled length of plastic pipe, hence the 80kg/80L

 That will work because it is not a point load.

 

If you are a handy guy you can make a nice panel from two pieces of corrugated roofing pop riveted together. You have to come up with a cunning plan to seal the ends of the "tubes" and pipe it up.

 

Or you can attached copper pipes to a corrugated sheet. Of course it all works better if it is under glass

[bluesofa]

21 minutes ago, VocalNeal said:

 That will work because it is not a point load.

 

If you are a handy guy you can make a nice panel from two pieces of corrugated roofing pop riveted together. You have to come up with a cunning plan to seal the ends of the "tubes" and pipe it up.

 

Or you can attached copper pipes to a corrugated sheet. Of course it all works better if it is under glass

 

Yes, I have to work on that.

I realise I will need to put the completed unit under glass to keep the heat in and wind/rain out. The 'on the ground' testing first will take some time, so I can work out these other details while that's happening.

That will be my cunning plan, thank you Baldrick!

[johng]

You could have a solar panel run a pump to circulate the water,then the angles won't mater.

Just leaving a garden hose out in the sun can produce extremely hot water so a large coil on the roof should work well.
One of those stainless steel water tanks in direct sunlight would help the heating too.

[cooked]

17 hours ago, bluesofa said:

OK, the full story:

It’s for a solar hot water panel, and it is actually a coiled length of plastic pipe, hence the 80kg/80L

 

The reason I didn’t explain what it was for, is that on another forum over a year ago, it just encouraged trolls to call me ‘a tree hugger’ and other abuse when I was asking about the same subject.

A case of once bitten twice shy. I hope it doesn’t start people trolling again, now I’ve explained the details.

 

Details please, I am thinking of doing this myself. 80 litres is about right for filling a bath.

[bluesofa]

16 minutes ago, cooked said:

Details please, I am thinking of doing this myself. 80 litres is about right for filling a bath.

 

The water quantity on the roof is not the end of the story – for myself.

As I said, I’m using the pipe initially to do some testing on how well the sun heats up the water in it.

If everything works out, eventually I plan to connect it to a 200L water tank to heat that amount of water for domestic use.

However, if 80L is enough for you, then buy 100m coil of 32mm diameter LDPE pipe for 1,000 Baht and try it for yourself. That coil will hold about 80L of water.

 

(edit) BTW, wrapping that size pipe into a single row flat coil will give you an outside diameter of 2m. This is as far as I've got, see the attached:

 

[cooked]

3 minutes ago, bluesofa said:

 

The water quantity on the roof is not the end of the story – for myself.

As I said, I’m using the pipe initially to do some testing on how well the sun heats up the water in it.

If everything works out, eventually I plan to connect it to a 200L water tank to heat that amount of water for domestic use.

However, if 80L is enough for you, then buy 100m coil of 32mm diameter LDPE pipe for 1,000 Baht and try it for yourself. That coil will hold about 80L of water.

 

I leave the garden hosepipe out all day, the water quickly gets much too hot to use on plants or touch. It works, that's for sure. 

[VocalNeal]

1 hour ago, bluesofa said:

wrapping that size pipe into a single row flat coil will give you an outside diameter of 2m. This is as far as I've got, see the attached:

 

Will take about 2 1/2 hours+ of optimum sunlight to raise 200l of water from nighttime  28 to normal hot water 62. 

 

The problem is what to do when the 200 l is as hot as you want it!

[johng]

If it gets over 100 you could start generating electricity...back to the steam age