How to attach a pergola mounting board to a steel frame house?

[Sam94]

Hi there, 

I was hoping someone might be able to help me get a better understanding of how to attach/build a pergola when the main house has a steel frame. 

My concern is that the roof trusses that you would normally drill through the fascia to mount to are in a “C” shape instead of a solid wood beam. 

Each truss does have a versatile rafter bracket that mounts the fascia and gutter to the frame. I’m just not sure if this bracket would be safe or strong enough to the mounting board too. 

The ideal goal would be to build a 8m x 3m open frame (no roof) pergola along the side of the house, with the 8m length being attached. 

Thanks in advance!

[EricL]

Hello @Sam94

Welcome to the Bunnings Workshop community. It's marvellous to have you join us, and thank you for sharing your question about attaching a mounting board to your steel rafters.

That is indeed an excellent question, the first thing that comes to mind is would you happen to know the company that built the house? They would probably have the engineering specifications of your steel rafters. I recommend engaging the services of an engineer to assess whether the steel rafters can take the stress and weight of a pergola.

I suggest taking into consideration building your pergola as a free-standing unit. In this way should the rafters not be suitable, you can still have your pergola built.  

Let me tag our experienced members @TedBear @tom_builds and @JoeAzza for their recommendations.  

If you need further assistance, please let us know.

Eric

[tom_builds]

Welcome to the community @Sam94 and thanks for the tag @EricL.

Do you have a photo of one of the roof trusses that you could share? That would help us to understand the roof geometry and give more specific advice.

Depending on the size of the steel used in the trusses you may be able to bolt fascia brackets to the side of them - as you would to a wooden rafter, but I can't speak to the impact that would have on structural integrity and strength of the frame.

[Sam94]

Thank @EricL and @tom_builds - The build was done through GJ gardener and the frame was specifically made by hytek steel framing. 

I have attached a photo below of the frame exposed that the fascia attached. I have also attached a copy of the truss plan submitted to council originally

[EricL]

Hi @Sam94

Thank you so much for posting the photos of the steel frame. Looking at the size of the rafters, I'm afraid they are not meant to take a great amount of weight. The area you are proposing to install the pergola will have to be re-inforced. There are many factors involved when weight and force are applied to a rafter. Not only will it have to hold the weight of the pergola, but the forces exerted on it when the weather is bad. All of this has to be taken into consideration before they sign off on the plan. Any unplanned modification could have serious consequences. 

Is the house now finished or is it still in the assembly stage? If it is still in the assembly stage, it would be the best time to consult your architect/engineer about your plans of installing a pergola. They can then make the necessary changes to your rafters. 

Please keep us updated with your progress, we look forward to seeing the start of your pergola.

If you need further assistance, please let us know.

Eric

[tom_builds]

Thanks for uploading those photos @Sam94 they give a good look at how the frame is put together. As @EricL mentioned having an engineer take a look and offer their opinion would be best.

From a non-engineer's point of view, I would imagine the most suitable spot to attach a pergola beam to the frame would be where the top wall plate meets the rafters (the frame would be strongest and stiffest here).

Roof extenda makes a bracket for doing this exact thing in wooden framed rooves, but I'm not sure if it would work as they are designed for bolts, tech screws may be too small to use in them.

If you know any engineers/draftsman might be worth asking them a quick question as too whether they think that might work.

Best of luck.