How to attach an aluminium pergola to house?

[Herbie28]

Hi, I'm planning to attach the 5m aluminium ledger board of the pergola (105x50 profile) to the house. To be specific, the house is a timber frame with high density polystyrene foam infill for insulation. There is textured rendure over the top of this.  

I plan to use stainless steel M12 bolts to affix the ledger board to the house's solid timber wall plate. The thickness of the plate and foam is near 250mm not including the plasterboard on the inside. 

I need to seal the gap between the facia of the house and the top of the powder coated aluminium ledger board. It's an open pergola (no roof) but water could penetrate the bolt holes or create staining on the facia when dirt and dust is washed down. How best to seal this ? With flashing  or sealant ? If flashing ... what type? An adhesive type? 

I have one question regarding the affixing of the pergola ledger to the facia. Is it OK to flush mount them or do I need to use a packer or stand-off between the two to do so? I'm not sure if there's "best building practice" or building regs that suggest otherwise. 

Thanx in anticipation of any assistance or advice.  

[EricL]

Hello @Herbie28 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about attaching an aluminium pergola to your house.

Before you begin, I suggest checking the rules and regulations of your local council regarding the attachment of your pergola structure to your house. Because you are attaching a structure to your house, it becomes more complex and requires more regulations. I also recommend engaging the services of a builder as they will be able to determine if the wall plate is strong enough to hold the structure of the pergola in stormy weather. 

I propose taking the following into consideration. When attaching a pergola ledger board to a house with a timber frame and high-density polystyrene foam infill, it's essential to ensure the structure is secure and properly sealed. Since your house has textured render over the insulation, using stainless steel M12 bolts to affix the ledger board to the solid timber wall plate sounds like a sturdy approach. Given the thickness of your materials, ensure the bolts are long enough to penetrate deeply into the solid timber for a firm hold.

To seal the gap between the fascia and the top of the aluminium ledger board, flashing would be a more robust and lasting solution compared to sealant alone. A suitable option available at Bunnings would be a self-adhesive aluminium flashing tape, which is flexible and can conform to the contours of the surface. This will help prevent water penetration and protect against staining from dirt and dust runoff. 

Alternatively, you could use a rigid flashing material, such as Colorbond or similar, secured with appropriate fasteners and sealed with a high-quality exterior sealant for added protection.

Regarding the mounting of the ledger board, it’s generally advisable to use packers or standoffs. This practice helps to prevent moisture buildup between the ledger and the fascia, which can lead to rot or structural issues over time. Using spacers allows for airflow, which can help keep both the house and the pergola structure in better condition. While there may not be a strict building regulation mandating the use of packers, it aligns with best building practices for long-term durability and performance. 

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

[Dave-1]

Good Evening @Herbie28 

I do like @EricL's description of how to. I also agree with the finding out from your local council to the rules for attaching a pergolla to the side of the house.

I would follow @EricL 's how to for what you are asking. Here is my prefe4rance

I much prefer to have it as a seperate structure even tho that requires some bracing and more posts I do think its worthwhile.

-With a seperate structure there is less chance of damage with winds (I remember you said yours was open) The length of the bolts required does concern me as they still need to go into timber after that 250mm distance.

-The house is still intact and no added strain to the eves or header boards.

-Seperate pergolla means you can modify it without having to worry about the house structure and waterproofing.

-By passing certain councils rules is a big one for a seperate pergolla

Dave

[Nailbag]

Hi @Herbie28 

There are quite a few variable to the questions you're asking. So my return question is if this structure is or does it need council approval? If so, then the approved building plans will provide all the necessary information as well as the advice from the building surveyors assigned.

Nailbag

[Herbie28]

Thanx for responding. FYI... pergolas less than 20 sqm, no roof, less than a certain height (I forget) don't require planning or building permission. This is a satate government and local council reg. 

[Herbie28]

Thanx for responding. FYI... pergolas less than 20 sqm, no roof, less than a certain height (I forget) don't require planning or building permission. This is a state government and local council reg. 

I agree re a separate structure and the ease of modification. 

[Herbie28]

Hi Eric and thanks for your most enthusiatic and detailed response. I really hadn't expected that level of consideration and detail. 

I'm chuffed that you have taken the time to provide a full and considered response!

I shall go with the self adhesive flashing over the union between house and pergola. There is an existing timber pergola there which I'd not mentioned.

I agreed with Dave that a separate structure would allow for modification and less concern about structural impact on the house. It's a small yard and attachment to the house means less posts in our case.

We also thort we would need planning and building permission but not so. We checked with the Stonnington Council after seeing the state regs. Pergolas less than 20 sqm, no roof, less than a certain height (I forget ... 2.8m?) or depth don't require planning or building permission. This is a state government and local council reg.