Steel vs Aluminum for Frame Work

Thank you.

I am dead set on a shade cover. Years back when the big Tupelo's and pecan tree where there, we never saw 100F in the attic. Now, since we have wide open sun from 10:30 through 4 PM, the attic is unbearable and I suspect causing more heat on the roof.

The roof is soon to be repalced with a steel roofing.

Thank you for your thoughts.

Steel is good. I would still paint it white.

However, if you are determined to do it I think you will find that it will be cheaper to just air-condition the attic, even with the cost of electric.

Or, you can just pay to have some large trees planted and have natural and beautiful shade.

What about air conditioning or a big exhaust fan. If you have an attic space, install automatic exhaust fans to draw out trapped heat. I too am not crazy about the shade cloth idea.

I have never had any model of automatic ventilator last. In fact I have huge vented openings on the sides of the house as well as under the eaves. No help.

I have experimented with shade cloth and vinyl tarp at the net shop and it dropped the temp inside the building to a workable degree. We discussed that on this forum last year. I've been here 37 years and the first 30 or so years were no problem as we had several huge trees that kept the house in shade 12 hours each day. Now they are gone ( hurricanes).

I am a believer that taking away that direct sunlight from either the present asphalt roof or the soon to be metal roof, will drop the inside Attic temp and that will transfer to less strain on the inside the home AC.

I just need to know, structurally, piping or tubing.

Thank you again for your input.

Some thoughts on this. It sounds like a building frame to enclose a house with room to spare, but with "shade cloth" on the roof only. If the shade cloth, or its connections could be reliably made sacrificial at a specified wind speed, the structure might be reasonable.

I would certainly use steel shapes, providing that I took on the design of such a job, but I would have to be desperate to do so. The difficulties of defining acceptable failure look immense, and to try to design for no failure would be expensive.

Thank everyone for their comments so far.

I have a design that will work .... as it is used on hot houses down here. I am just going a little larger.

I already make netting structures with built in fail safes. This shade cloth business is quite easy. The reinforced edges will have netting sewn in to replace grommets, making the structure spread the strain along the entire edge rather than just at the 24" spaced grommets.

This one will have a 90 psi test zipper system that allows me to pull the shade cloth off in under 20 minutes.

Still, I am wondring , tubing or pipe, aluminum or steel.

thank you all for your input.

I use "coolaroo" sails and just stretch these with cables and rollers.

Works well on my patio for 6 years now. Still strong.

Easy to remove when huricanes come. although they have been up for the last 6 years.

They withstand strong winds too. No structures needed, just some pole ends.

It is even beautiful. People stop to watch.

Actually, it might be cheaper to plant a row of poplars, and put up some army camouflage netting on poles with staked guy lines till they grow.

Hi Netmaker,

If you are already planning to replace the roof, why not go for an insulating layer UNDER the new roof to reduce the conduction of heat to the interior space. A colleague recently used some recycled coolroom panels (metal-2"polystyrene-metal sandwich layer) for some added roofing and the additional cooling was quite obvious. Your outside layer would then be cosmetic but the underlayer does all the insulation. There are all sorts of insulating materials; foil-coated building paper, mineral wool and fibreglass. Usuallly the problems is the roof is still there but since you will be removing to replace, there may be some better options.

He's a net maker. He really really really really wants to use a net

Here's an idea. I don't know how much this cloth weighs... but instead of using structural tubing spanning your roof across the 28', put up a single tall pole at each end of your house, string a cable across the 50', and use a couple or three auger type anchors in the ground and more cable as guy lines to help hold each pole up. Your traversing cable needn't be extremely tight. You can leave some sag. Drape your cloth over that.

Then all you need to build is another rectangular support along front edge of house and one along back edge, to attach the edges of cloth to. This is where you can use your structural material. You could have a peaked shade "tent", in essence, and not worry about a superstructure spanning your home. And also not worry about an extra 10k to 15k in costs, and permit headaches.

a little bit like the Lockheed factory during the war

http://andysredneckramblings.blogspot.com/2010/10/how-do-you-hide-enormous-aircraft.html

Cool! I want one of those!

Without a drawing of what you plan it's bit hard to guess ..

Post a picture of the roof and your plans.

1. Pipe is stronger, the jointg is the weak link; bolts rather than weld
2. Why not use wire and springs to keep tension
3. Or steel mesh on the roof with shadecloth or the solution below
4. Shade cloth will blow away and take the roof with it in strong winds, almost guaranteed.

Try this instead

1. I use 6ft x 10ft willow fencing under and/or above my pergolas and it works like a charm on a simple wodden batton frame
2. It stays there in high winds because it is round, with a minimal of wire fixing (unlike split bamboo)
3. Whole bamboo would also work
   
4. It rolls up in winter. Store it in a dry place and it will last 8-10 years
   

Roof insulation should be nice and thick, with vents near the pitch on both ends

If you have an evaporative air-con, open a couple of extra ceiling vents an let the airflow go into the ceiling space from the house interior and blow out of the roof vents. This will cool the roof space and the heat will not percolate through the ceilings. Be sure to keep outgoing airflow with sufficient back-pressure from your evaporative air con. Build verandas on the west side (ideally all sides) with open willow fencing on top to shade paths and walls: most of the heat can come from unshaded and poorly insulated walls, and concrete around the house.

If the climate is dry make a pulse spray pump to vaporise water droplets at regular intervals ( feed it from a clean rain water tank). good luck

I've done similar framework with 4" square tube / steel

Easy to work with, weld, source, maintain..

anchor posts into about 1/2 yard concrete each tie sections together with more 4"

I believe in shade too.. looks nice

4" square is great to work with, but he needs to span at least 30' across his roof. Unless he does some serious trussing, that is not going to work. And the crane to even assemble this thing will be quite expensive. He'd be building a steel house around his house. I don't see anything easy, inexpensive, safe or good about that idea. The shade cloth is one thing. But unless someone is a professional civil engineer and heavy ironworker, the completely enclosing steel framework for it is not something I'd recommend trying.

I have to agree that there would need to be few well placed truss components..

I only get 22' sections of 4". I consider it light enough to work with by hand and cranes are rarely a part of my equation.

I'd be more inclined to anchor six 12" vertical steel posts about 6' down and 12' high near the corners and higher at the peaks.

I would weld on my attachment points for cable.. install cable.. then then fit my sailcloth to the cable..

Or run more cables and grow vines.. many options.. That cooling layer of air is sooo..

anyway.. There are plenty of homes that use this type of shading.. very effective and pleasing to the eye when well thought out..

What you are describing sounds like a foreshadowing of the aftermath of a big blow.

A thermal barrier would be my choice, and it goes inside, protected from acts of God, or Satan, if you happen to be the one that gets hit.

You can do this on the pricey side with Mylar sheets sold for this purpose, or, you could follow the advice of an old report from the University of Florida that recommended going to Costco and buying several packs of heavy duty aluminum foil and having a diy day in the attic along with a staple gun and lots of cold beer. That study showed that the Costco solution was as effective as the Mylar at a fraction of the cost. You should also get some power vents to add above your thermal barrier to exhaust the trapped, reflected heat so it doesn't overheat your roof and also migrate into the living area of the home. There's also RBS (Radiant Barrier Chips) that can be deployed. In my experience with framed-in new construction pre and post thermal barrier, regardless of the type, it resulted in a good 25 degree difference.

Australia banned foil on ceiling because it became live with exposed wiring and killed a few electrical contractors. The foil is good on the underside of the tiles , or tin, where it poses no danger. In this case it needs a barrier, if installed under tin, to minimise condensation.

forget all of that crap and shoot polyurethane foam under the roof. If you have walls simply open them up with small slits and recover the entire wall with 3/8" drywall put extenders on the electrical boxes. This will increase the structural bearing of the wall and the roof. It will also keep the attic space 10 to 15 degrees higher than the interior of the home. I assure you this works as I have done it myself in the Florida sun... Good Luck..

I wouldn't do it, over here in the mother country we have a product called Kingspan which you probably have under a different name,it consists of 8x4 panels of poly urethane very dense,backed with aluminium foil,in some cases it will have a plywood sheet on the reverse side,this is cut to the width of the gaps between the roof frames & fitted to be flush with the under side of the wood, If your joists are 4x2 then use 4" thick insulation board,the aluminium side reflects the heat out in the hot weather & keeps the interior cool but will also keep the house warm in cold weather.

Check out a US company 80/20®inc. They have everything you need including formula in there catalogue to work out deflection/sag. They have distributors throughout the US

All good suggestions.

I think I need to re-evaluate my thinking on this. This is WHY I post on here before starting a project. You all mention lots of things I obviously did NOT consider.

I need to get in the shop now but I'll mull all of this over today.

Thank all of you for your thoughts. It is very much appreciatiated. I'll be back with some thoughts on what you all brought up.

Could not concentrate on work. The answer to this is so simple.

Installation of spray foam, panels and foil backing either requires me to be in the cramped space 60" at the highest, or is too expensive for my budget right now. I suspect they would work better but its just not going to be feasible right now.

On the other hand, I've installed giant depratory bird nets over 1/4 acre ponds, parking lots and inside enormous warehouses.....its the same principal and I have the experience in cable splicing, turn buckling, spring loaded tensioners, etc.

All I really need is shade over 80% of the roof.....period! It worked last year with the shop ( we had a big discussion on here about it). The shop is much cooler now, just with the fans. That over lay of 20 Mil vinyl worked extremely well. The wind has ripped it off twice but that is why i put the break-a-ways along the perimeter. I just drug it back up top and re-set.

The shade principle should also work on the house> I just need to make it a little more aesthetic looking for the wife.

I already know how to set fail safes for wind and how to make it easily detachable ( we use zippers that can take 90 to 140 psi all the time).

My welding is attrocious..... and 4" steel tubing to span 28'-30'....I'll never handle that.

So, its back to just substituting what Mother Nature took away.....tree shade. I have access to lots of materials ( the stuff from Australia being the best ) and I have 2 commercial sewing machines we use for sewing Nitex and Pecap for plankton nets.

I'm going to study the outlay and the angles and get back on here if nothing more than just to give you all an update. Thank you all for your input as you saved me from a costly mistake.

Its why I always run these projects through CR4 first. Many brains are better than just just my one half-a-brain. Thank you all again.

Probably the easiest and more lasting is the internal insulation already suggested.

However, if you wish to go over the roof, I would suggest a long lasting white
material - cloth if you prefer, stretched tight, but aluminium is preferred, due to its
conductivity, spaced by offset brackets approx. to be 2- 3 inches above the existing
roof (tiles, slates, whatever) with all the sheet end / sides open to the air.

The trick is to leave an air gap sufficient for the air (wind) to carry away the heat,
(which actually does the work of removing the heat, and not the sheet) while at
the same time not providing too much space between the sheet and the roof so as
to cause lift. 2 to 3 inches should be sufficient gap. Any air gap will help, but too
much will give lift off! Goodbye sheet(s)!

That is, no major structure is required.

Hope this helps. jt.

If the invisible man knocks on the door, tell him I cannot see him today.

You already have a "functional" roof. Why not just install a "solid" cover using 1/4" weather-rated plywood installed with the 8 foot lengths running the length of the house and with treated 2x4s running vertically at 48" spacing, just laying on the existing roof? Extend the "cover" just to near but above the gutter line, but extend the 2x4 past the gutter- more on that later.

At the roof peak, install another 2x4, 24" long- laying "flat" (4" side horizontal) on the other side of the roof, with some type of long screw run through to keep it generally intact on the roof ( a squirt of silicone under the 2x4 at the screw hole will assure no leaks from the screw penetration).

Use the same approach at the eave side, except have a 2x4 go down past the gutter and another turning in toward the house under the eave with a screw holding it in place at the eave.

In a hurricane, it will go away but it should stay in place "normally".

Paint the plywood gloss white using a high grade acrylic enamel exterior paint. Don't worry about any cracks- it is above a functional roof and the paint will drip in to cover most of the "exposed" edges.

The 3-1/2" spacing will allow any heat from the relatively cool plywood cover to vent away from the actual roof, so your attic will be the same temperature as ambient. It will be much less expensive, and more secure, than the cloth cover. And it will be very easy to remove when you are ready to re-roof the house.

I know this is not what you wanna hear but, it makes way more sense to upgrade your attic insulation when you change the roof to metal( So you said). All you need is a few days of nice weather and you could totally open your roof so lots of space to work. It sounds like you are capable of doing the work yourself , the cost of the insulation I'm sure, would be no more than the cost of Screening, Pipes or poles turnbuckles and pulleys etc. and the biggest plus is it would be Maintenance Free for life. Yours would require constant resetting , useless on really windy days , no winter benifit. Painting most years to keep it looking ok, maintenance and replacement of ropes and pulleys and eventually replacing the screen at some point , all at a cost.

And the looks.........on your house.....well thats another subject.

After all is done, upgrading the Insulation is a by far better way to go, in material costs, labour, and Maitenance Free for-ever.

Just my opinion...Rescue

Rescue,

I've got two projects with this roof.

One is that I am having 15-18" blown in fiberglass.

The second is I am having a 26 gauge metal roof installed over the asphalt roof. I am not removing the old roof as it is still in very good shape, I just want the steel roofing for added strength during the hurricane season. During the last two big storms, homes with the steel roofing screwed in held up much better.

What more insulation could I add?

"The second is I am having a 26 gauge metal roof installed over the asphalt roof."

If it is the aspahalt roof I know it is probably one reason why it is so warm inside. Asphalt would be the ideal material to maximise heat absorption and maintain a warm environment. Anything you can use to cover the asphalt will giver you good results. It is possible that your 26 gauge metal overlay is going to be the greatest contribution to minimising the internal heat. If you can add a layer of insulation between the metal and asphalt it will only improve more.

It would be interesting to have a few temperature measurements, ambient and inside, before and after your planned mods. Good luck and keep us posted.

Or... he could just paint the asphalt white with white roof coating. But he wants to strengthen it too, based on seeing neighbor's steel roofs (why isn't it "rooves"?) better surviving the storms.

I understand your reasons for applying a metal roof, and even though I dont agree with it I understand your reason for want to put up a sun screen , what I don't quite understand is why you would leave ashpalt shingles on your roof under the metal that will suck in the heat durning the day and hold that heat in the attic and then emit the heat that it itself has held into your attic long after the sun goes down. Then you wanna put up a sun screen to block some sun because the attic is to hot. The screen will block some sun but then again the shingles will hold all the heat it will get. After the metal is on its to late to remove the shingles unless you wanna pay the man again. In my opinion ............the benifits for removing the asphalt shingles far out-weigh the benifits of leaving them there. Doesnt this seem like one thing defeats the purpose of doing the other thing.....Sorry dont really mean to rag on ya but just how I see it...........Rescue

Actually, If I recall the roof is fiberglass shingles. No one down here takes off the old roof when screwing down this type metal sheeting. Even the old roofers say let it alone.

If the roof is really old, then they remove it. Otherwise if just stays in place.

The shade sail concept works. I've tested it at my shop, which is also a metal roof. The second unseen benefit is that it is really nice looking in a odd way. I think it will make the old house look so weird it will be unique.

The 15-18" of insulation will help a lot. The shade sail will just completment that by killing that direct sunlight.

The "look" will be unique now that I've studied it more. No frame work just some cables which I have in abundance. If it does not work out, Its just a Saturday moring to take it all down and I've got a big ol' piece of shade cloth to stretch out over some part of the yard for the grandkids to play under or for us to bar-b-que.

Thank you for the input .

Re: the benefits for removing the asphalt shingles far out-weigh the benefits of leaving them there

I'm not so sure that's the case:

• although in aggregate, they are heavy, I don't thing they really have that much capacity for heat storage
• under a reflective metal roof, they will not gain as much heat
• the alternative is disposing of them in a landfill, at the cost of (1) labor to remove them, (2) cost to dispose of (rental of a dumpster, etc.). Finally, are they considered a hazardous waste? If they're old enough to be asbestos shingles, I'm sure they would be, although I suspect they are not that old--I think asbestos shingles stopped being used circa 1979-1980. (Mine were fiberglass, and the OP says his are fiberglass--now I guess the question is whether asphalt is considered a hazardous waste)

Finally, I wonder if the extra mass and such helps keep the roof on in a hurricane situation?

As you're dead set on an awning and we can't talk you into insulation, Out of Box,s reply (Post 12) is close to the solution I would go for. I differ on draping the sail over the wire, it will chaff and wear through in no time.

The sketch below shows what we are both talking about in it's simplest form. The six posts are mounted on pivots and 8mm steel guy ropes attached to ground anchors act to tension the awning. A further steel wire is attached to all edges of the cloth to relieve the fabric from most of the strain. You may want to add more short posts along the sides.

The posts are in compression so would need to be steel. 4" pipe for the long pole and 3" pipe for the side poles Schedule 40 should be more than enough, you just want it big enough so it won't buckle. I did the drawing roughly to scale, and the long posts shown are 7m (23') and the short posts 4m (13') The cloth is not square it is a hexagon with two long sides.

Make the slope of the awning a bit steeper than the roof slope. Wind (air) passing under the sides at the eaves will have to expand as it passes over the ridge. This will create a low pressure zone that will try to pull the cloth down onto the roof rather than trying to rip it away. Don't make the difference too large, low pressure over that big an area could lift your roof off. The curved shape of the cloth (it needs to the taught so it does not flap in the wind) has a similar effect on pressure, for more info, read up on how a sail boat goes faster than the wind.

Good luck, I think the hardest part will be convincing your wife.

Good drawing JHH.

Decent plan, but here are a couple options. Yes, draping the cloth over the cable would tear it rather quickly, and your design might work better. But I suspect with netmaker's netmaking skills, he might be able to sew an appropriate layer or two of reinforcement material along the underside of that ridge. Maybe a meter wide, or so. Something thick and durable.

The other option is what I poorly described in post #12. It is somewhat more like what netmaker described, in that... the two long edges, instead of just having those edges hemmed over a long cable, and poled at the corners as you've shown... He could actually build a partial framework. Two shorter poles at each end of each long side, cemented into the ground. And a long pipe or rectangular tube from one post to the other. With two additional supports somewhere between (depending on where his windows/doors are). This way, instead of just catenary cable supporting the long sides, he would be able to attach the entire length of each long side to something solid. Would eliminate any hot points of high stress on those long edges. And would eliminate the need for all those additional guy wires on each corner. Might look a little cleaner, too. No flapping edges, except on the two short ends. Take-down would also be easier, especially if he uses those zippers he's talking about. And using rectangular tube for the two horizontals would make attaching the cloth to it easier... instead of using round pipe there. Bolting is easier too.

(by the way, this spell-check doesn't recognize "catenary")

Shade cloth from personal experience is a good choice to improve the livability of your house.

When professional outfits cover carparks or fit sails over pools etc in this country they use galvanised box section or galvanised round tube. Galvanised or stainless cables between staunchions is another common method.

Just beware of loading from hail (or snow if applicable) in the design.

Dew will not form under shade cloth which can be a good outcome or a bad one depending on your needs. Bad if you want to collect the extra water.

It was an old fisherman friend from around Carpenteria that first told me about shade sails a decade ago. He said you all use it all over the place. Its just new around here. I am going to be the first one in this location to hoist one up the mast! ha ha!

Thank you and I hope you all have a nice winter.

I'm sure your sails will be plenty strong done this way.

Something else from personal experience that may interest you. When we had our roof replaced around 12 years ago I did it with Zincalume (Galvalume in US) custom orb but had an anticondensation blanket fitted. There are 2 reasons for this: 1. It keeps the heat right out of the building as the blanket contacts the iron. 2. By stopping the condensation inside the roof is reduces the corrosion in the overlaps which is what kills a roof.

I also made sure the roof was lapped the opposite direction so the prevailing wind would not deposit salt under the laps as it had with the original.

Now the zincalume has faded to grey I'm planning to paint the roof, when I get time (yeah what's that). With hindsight I may have been better with Colorbond classic cream or similar. Zincalume is great for several years but does grey off and absorb more heat for the blanket to try and keep out.

Anyway the bottom line is a house at least 5 deg C cooler than neighbouring houses with no blanket.

What is orb?

Can you tell us any more about an anticondensation blanket--is it fabric impregnated with something to prevent corrosion, or is it an impervious (or pervious) fabric that somehow allows condensation to migrate away from the Zincalume?

I could google, but it's easier for me to ask ;-)

Go with wood. After all you're building a tent over a house.

Naw! a tent is big ol' thang anchored down to the ground. This is going to be a beautifully colored Sail that makes shade. It'll float and sway. Every Cajun in the parish is going to want one! I may stop building fish nets and start a whole new line of product.

......and yes, there will be guaranteed repeat business...........right after every ou'ragon ( hurricane).

From the standpoints of absorption, reflection, and emissivity, I believe that Cerama-Tech would be a good coating for your roof (whether metal or plywood). As coatings go, it may be on the expensive side, but still worth consideration.

This is not exactly an endorsement, though. The product is also being marketed as having a high R value. This may be true, but even at an R of 100 per inch, a typical coating thickness of 0.005 would give only R = 0.5. (Or thick 0.010 coating R = 1.0.)

I have wrestled over this with the marketers here on CR4. They have been trying to get third-party certification of their claims, but I am not up to date on how far this has gotten. My best wishes are with them, even though I think they are confusing some issues.

I recently used a couple gallons of similar stuff.

It was like using thin white paint that had some chalk dust mixed in..

Better sales through marketing.. not impressive at all.

If you're abosolutely set on a shadecloth superstructure, and as you've mentioned your welding is "attrocious" you may want to go down the road of pipe. That way you can use standard fittings to hold the thing together (and run water through them to spray anything roosting underneath).

Considering the quantity of parts you'll be buying for this build you will want to source some pipe fitting suppliers for fittings, or find a company that installs piping the size you're talking about (this will save you on tool cost and time to build, but increase the overall cost). You'll be needing a significant number of X, T and Y junctions, as well as either barrel unions or swivel fittings.

Good luck and stay cool!

Thank you. I didn't think about some peep holes to run water through. Good Idea.