The choice of whether to add a roof to your container or not is made up of both personal preference for the style and also the cost. Clearly, not roofing your container will save you money initially. However, in the long run installing a roof and insulating it could save you money in energy bills.
Because hot air rises, the majority of the heat lost in your home will be due to it escaping through your roof.
When making this decision, consider that having a roof allows you to insulate inside of the roof which will help to maintain and keep the inside temperature consistent. Having a roof with an overhang keeps the rain from running down onto your windows and removes the need for a drip bar above the windows.
Different Roof Styles
A shed style roof, shown below, is essentially a sloped roof. The advantages of using a shed style roof are that it is extremely cheap and very simple to build. A roof like this can be made and installed in a couple of days. The long, sloping roof also lends itself well to solar panels.
To install a shed style roof on your shipping container, weld right angled steel plates across the length of the shipping container on both sides. On each side of the container roof attach a wooden beam into the steel plates. Screw the trusses into this beam. Now, the roof’s basic structure is starting to take shape. Attach purlins or steel bars for structural support across the trusses to complete the roof’s structure. For this step, you can just add 20 foot long purlins onto the trusses and you’re done. Next, your trusses need bracing to protect you again the wind.
This is when you will depend on your structural engineer for specifics. This professional engineer will be able to advise you about the exact load bearing requirements needed for your roof. This figure varies regionally as it takes into account natural stresses imposed on your roof such as rain, wind and snow loads.
To cover your roof, you can use either shingles, galvanized metal sheets or coated steel sheets. Coated steel will be the most durable, however galvanized metal sheets are very easy to fit and are also quite durable.
The final stage is ensuring your roof has sufficient ventilation. To do this your trusses should overhang the container as shown below. Attach a fascia and soffit board underneath your trusses. The soffit board should have at least an inch air gap in the middle of it, covered with wire mesh which allows air to flow in and out of the roof.
Make sure you allow for ventilation at the gable ends. Do this by simply cutting slots out of the steel using a disc cutter. This will allow air to pass through the roof and avoid heat traps and condensation which causes rust.
Your next option is to use a gable styled roof as shown below. A gable styled roof is what most people imagine when they think of a traditional home. It has the distinguishing triangle look. The advantage of using a gable roof is that it has a sloped roof which provides great water drainage. This makes it less likely to leak and helps extend the lifespan of your roof. It is popular because it also provides more ceiling space than other roof styles.
The construction of this roof is similar to the stages detailed above for installing a shed style roof.
To install a gable style roof on your shipping container, weld right angled steel plates across the length of the shipping container on both sides. On each side of the container roof attach a wooden beam into the steel plates. Next, screw your trusses into these wooden beams and the roof’s basic structure is starting to take shape. Now attach purlins across the trusses to complete the roof’s structure.
Like the shed style roof, you can either use shingles, galvanized metal sheets, or coated steel sheets.
Now make sure the roof has sufficient ventilation. Trusses should overhang the container as shown below. You can then attach a fascia and soffit board underneath your trusses. The soffit board should have at least an inch air gap in the middle of it, covered with wire mesh which allows air to flow in and out of the roof.
A flat roof, which the shipping container already has, can be adequate for some people’s needs. Although it’s clearly cheaper not to roof your shipping container, this does leave you susceptible to water pooling on the roof.
If you decide not to roof your containers, a quick safety barrier should be installed. Lay a tarpaulin sheet onto the roof of the container and overlay this with rolls of asphalt. This will provide you with a layer of defense between the dampness and the container’s roof.
Importance of Having a Structural Engineer
Whichever roof type you choose, make sure to work with your structural engineer to calculate the load bearing requirements of your roof.
To do this they will calculate the dead, live, and transient load of your roof.
- The dead load includes the combined weight of all the materials which were used to build the roof (i.e. trusses, purlins, roof tiles).
- The live load is the weight of any equipment and people who work to install the roof.
- The transient load is all of the natural stresses placed upon the roof such as rain, wind, and snow.
The load bearing capacity of your roof is the total weight the structure of the roof can carry without the roof collapsing.
Each local area will face different challenges. For instance, certain areas prone to high winds will need roofs with additional bracing for the trusses. Warmer climates, with a light breeze, don’t need a roof with very strong structural capability but need it more for the insulation benefits.
All of the roof types need to have adequate ventilation to prevent condensation.
Let us know how you decided whether to install a roof for your container building.