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Chapter 8 of 29

sun roof
  Aug 20, 2013

Chapter 8 - Building a Water Catchment Sunroof on a Shipping Container


sunroof on shipping container house

Early on in the research for container houses I saw a picture of a container dwelling in Australia that had a large sunroof for shade and water collection. This seemed like an excellent idea. I have added only one caveat, my containers need to be movable.


Concepts and ideas

With the containers in place on the temporary location it became apparent very quickly that I needed a water supply. Carrying water to the site became a chore very quickly. When full summer arrived and the temperatures soared, the inside of the containers became overwhelming without the doors wide open. I started on the sunroof. I need it to be:

Cyclone proof

Easy to maintain

Easy to build on my own

Capable of being dismantled

Part of the container and without separate foundations

Easy to add to as the project unfolds


Video References

Sunroof for catching water

I decided that I wanted to lift the sunroof above the container roof by 0.5m (500mm). This would give me a crawl space to be able to access any part of the roof for repairs or modification. The wind would provide passive air conditioning to prevent a layer of hot air building between the sunroof and the container top.

sunroof construction on shipping container house

I built the prototype sunroof at the temporary site. It was a success and I was happy with it. I only put up 3m x 3m as I knew I would be moving them. It would be simple to extend when I needed to.


sunroof construction on shipping container house

The following sequence shows how I build the sunroof. This occurred after the containers were moved to the final site. I start with a blank container roof.

sunroof construction on shipping container house

The obvious points to attach a roof are the four large metal castings in the corners. Steel generally comes in approx 6.5m lengths. I find that 3m lengths were more manageable for one person.

I purchased metal plates from the local metal supplier. 150mm x 150mm x 10mm (6 inch x 6 inch)


sunroof construction on shipping container house

After consulting with a friend we came up with the design I have used successfully. It consists of a plate that sits on the corner casting, with a metal post going vertically and a bolt and steel peg to hold the whole thing in place on the corner casting. The peg also provides an excellent anchor point for further development.

sunroof construction on shipping container house

Here is the corner post assembled.



Welding

I asked my friend to weld the post to the plate. He suggested I should buy my own welder and do it myself. I had never used a MIG welder and did not know how to do it. I researched welders and with my friends guidance, purchased a lightweight MIG welder (inverter technology) 200 amp capacity. This would allow me to weld the 10mm steel plates. I have since used my welder to weld to the metal castings and can recommend this as a purchase.

The welder needed a substantial electrical power source. Under guidance, I purchased an inexpensive petrol driven Chinese generator with a good output. This has proven capable of driving my welder and I can recommend it.


Instructional welding videos

I watched 2 significant welding videos on you-tube that gave very clear advice for the novice. Armed with this information and some friendly supervision from my friend, I practiced welding on test pieces. I very quickly progressed and welded the upright post to my plate. It turns out that welding is easy. I would like to thank the kind gentleman that posted the videos.

Basic MIG Welding

Advanced MIG welding

Construction - Continued

I needed to cut my metal posts. I made a trip to the local major hardware store (Australia - Bunnings) and purchased a large metal cutting saw (drop saw). It can take different cutting wheels and will cut stone as well as steel. First attempts to use it were a little scary, but I am now quite used to the noise and sparks it makes when it is operating. I also purchased a baby hand held grinder, 100mm, to allow me to clean up the sharp metal edges from the cutting process.


sunroof construction on shipping container house

I needed to anchor the roof to points between the castings. I marked out the center of the container and then divided that in two, which gave me approx 3m intervals. I cleaned the surface paint and welded a piece of box section steel, 50mm x 50mm x 4mm wall, galvanized, to the outer edge of the container roof. I pre-drill the bracket with 13mm holes to take the uprights that would bolt to it.

After correcting for the difference in height between the casting and the roof section I quickly fabricated posts to attach to the brackets I had just welded on. I now had 4 upright post with one side 100mm taller to provide a slope to a gutter.

For the post, I used 40 nominal bore pipe, galvanized, medium wall. This is the pipe that scaffolders use to assemble safety railing structures around buildings. The metal shops sell the bolt on couplings quite inexpensively. (A subscriber to my blog in Brazil was unable to find them locally. He found them when he searched under fencing equipment). I considered how far to allow the roof to overhang. A large overhang would provide more shade. It might also need more support. I also considered the possibility of extending the roof in any direction. I decided keeping the overhang short would be my simplest option. Midday sun was my main concern and at 12:00 it is directly overhead.


sunroof construction on shipping container house

I cut two 3m lengths of tube and this was anchored at either end to the uprights on the castings. I repeated this for the first set of internal uprights.


sunroof construction on shipping container house

This picture is a close up of the cross bar fittings. Afterwards I cut two lengths of pipe to fit neatly into the gap, approx 20cm from the end. This I bolted in place with appropriate shaped couplings. I now had a 3m x 3m framework on which to support a roof.


sunroof construction on shipping container house

I went in search of sound advice. My search ended up at a set of pdf tables and drawings from a steel company. They provided detailed tables that allowed you to work out the thickness and profile of steel you would need for any given structure and dimension of roof. This was excellent. I was now working with sensible information.

I selected the low pitch, metal sheet, roof tables, and then I simply had to look up the length of the rafters, and battens. It gave a diagram indicating the correct terminology of the roof components as well. I purchased the recommended profiles of steel. To verify the results I started to look at all the buildings, carport's and metal structure roofs in my environment. My roof components looked sturdier than any that I had seen and I proceeded.


sunroof construction on shipping container house

I secured the rafters to the round pipe with U bolts. I made sure all the unions on the roof were VERY tight.


sunroof construction on shipping container house

I then bolted on some metal brackets I made from "unistrut" steel found in the environment and these allowed me to bolt on gutter boards. These are wooden planks mounted vertically to provide a surface to bolt the gutter brackets to. I used string to mark the line of the gutter . I tested the fall by tipping water onto the roof and it flowed correctly. I simply added a down pipe to direct the water.


sunroof construction on shipping container house

Here I am bolting the gutter boards to the uni strut.


sunroof construction on shipping container house

The fall line was marked with string to ensure the water drains correctly.


sunroof construction on shipping container house

I placed the gutter section into the supports and then I secured the battens to the rafters with tech screws.

My friend pointed out that my costs were excessive. He thought I should weld everything in place. It would save the cost of all the couplings and expensive U bolts. He was correct, but I valued being able to dismantle the roof more highly than the price of the fixtures. I located a source of second hand, reasonable quality, painted corrugated steel roofing tin. It was slightly longer than the 3.08m I needed. (the .08 comes from the distance added to allow the water to fall into the center of the guttering). It had holes in the steel where it had been secured in the past. However the holes are in the peaks and not the valleys of the corrugation, and it turns out it was highly suited to my purpose.


sunroof construction on shipping container house

I had to cut the ends square, and to my desired length. I made a jig / guide to allow me to cut the ends square whilst holding the tin flat. I cut the steel with a regular electric circular saw. The jig is just two lengths of steel and some wooden blocks glued in place to align with my corrugation pattern.

I painted the raw edges with galvanizing paint.


sunroof construction on shipping container house

I secured the roofing tin to the battens with tech screws. The roof is starting to take shape now


sunroof construction on shipping container house

This picture shows the first flush water diverter that cleans the roof and discards the first 9 litres of water off the roof. The sun roof makes a very big difference to the heat in the containers.


sunroof construction on shipping container house

I added a safety rail. This is a horizontal pole secured to the frame. It allows me to secure a ladder to the roof frame and not be leaning on the end of the tin. I can tie my ladder to the horizontal tube at the top. With this I can climb onto the roof safely for inspection and maintenance.

The sunroof provides approx 36 square meters of area to collect water. It drops the temperature of the container roof significantly on a sunny day. I was able to dismantle and reassemble it. I build the sunroof on my own and I attribute this to the fact that all the metal lengths are approx 3 meters. This allows me to maneuver them on my own safely.


Moving the containers

I had to remove the roof for the crane to pick them up. The side loader driver insisted that I take everything off. He allowed me to leave the 50mm welded on brackets in place but pointed out that the containers were now taller than legal and he could be in trouble if he was stopped and checked for height!!!

When the containers were placed on new foundations at the final site, the framework went back on in a day, and by the second day the entire roof was assembled and working.

Materials & Costs (for 1 sunroof)

I estimate the cost for the entire roof, assuming new roofing tin, is $2500

Frame, 4 x Corner plates $15 each, $60

Frame, 8 lengths 40 nominal bore pipe, medium wall, 6.5m @ $55 each.

10 Brackets to hold uprights to container frame, 50 x 50 x 4mm wall, galvanized,150mm lengths.

Rafters, 11 rafters of 3m, 65 x 35 x 2mm Galvanized, 1.2 meters apart. One length is 8m, $72 per length.

Battens, 3 battens of 12m, 25 x 50 x 2mm Galvanized, 1.45 meters apart. Length is 8m, $46 per length.

20 couplings, T pieces $6.50 each, X pieces, $9.20 each.

U bolts $150

15 square meters of used roofing, A box of beer!

15 square meters of new zinc alume, $300

Nuts and bolts and screws, $50

Spray paint, $50

Board for gutters, $40

Paint for gutter boards, $20

Gutter brackets, $20

Guttering, $50

Leaf guard, $30

Water pipe, $50


Tools

I estimate I spent about $1900 on equipment to allow me to fabricate and weld steel.

Basic power tools and hand tools

Welder $770

Gloves $10

Protective jacket $10 from a charity shop

Welding mask $40

Welding flux filled wire $120

Welders pliers $15

Welders brush $10

Petrol generator (capable of providing the current for the welder) $600

Extension leads $30

Drop saw $150

Face guard & gloves $35

Ear defenders - given

Baby grinder $35

Grinding disks $50


Hindsight & Wisdom

The sunroof was the catalyst for major spending. A lot of the costs were in purchasing the tools to allow me to fabricate with steel. These tools have been used repeatedly and have earned their keep.

I have to date not put a sunroof on the kitchen container. I have fitted the solar panels instead. I seriously considered many different methods of combining the solar panels onto the sunroof. I rejected each one for different reasons. I later extended the sunroof over the kitchen slightly to create a covered walkway, and I cover this in book two. It was simple to extend.