Covered patio on offset aluminum ledger

[eljay]

I am planning to add a covered patio to the back of our house, but want to avoid touching the house enveloped for many reasons, the main ones being that disturbing the house envelope just increases the risk of issues down the road and doing so requires a permit while free-standing cover/pergola doesn't.
Please don't try to convince me to just do a ledger board attached to the house. I really don't want to do it nor do I want to use lumber.
So, I devised this plan and I'm looking for tips, pointers.
This is the patio cover I plan to buy: https://canopia.com/product/stockho...clear&attribute_product-series-name=stockholm

To "attach" it to the house, I plan to use three Maine Deck Brackets (https://deckbracket.com/product/deck-bracket/) bolted to the foundation wall (the house is slab on grade). Then I will bolt to each bracket 4x1" aluminum square tubing, which will serve as the back posts and tie them across with a 16' 6x1" aluminum beam, which will become an offset ledger board. I will then attach the above patio cover to this ledger board.
Because I don't want to drill holes for the brackets too close to the house wall plate, I will likely have to put them below the patio pavers, which are 3" thick. That means that the pavers will need to be cut around the aluminum posts.

The brackets specs show a downward load capacity of over 1000 lbs/ft. I was planning to bolt to the concrete foundation using four 1/2" thick stainless steel wedge anchors with a tar paper placed between the aluminum brackets and concrete to prevent corrosion.
Can/Should I use Tapcons instead? I've never used them, but it seems like they will be quicker to install. Are they steel under the blue coating? Will the coating wear off during installation and eventually cause galvanic corrosion reaction with the aluminum brackets?

I'm not sure what thickness of aluminum to specify for the posts. I am thinking of 0.125" would be plenty strong and majority of the load I expect will be on the bolts holding them to the brackets, so I need to find suitable 1/2" stainless steel hardware.

The front posts of the patio cover will be bolted through the patio pavers and into concrete footings. Those posts are 6x6" 1mm thick aluminum. I realize that the pavers on the footings will stay planted while the rest of the patio may move over time.

Thank you for pointers on the above and any other tips.

 

[gregs]

No pointers, but what does something like that cost?

 

[eljay]

No pointers, but what does something like that cost?

The whole project? Way too much.
I'm expecting up to $15k including patio stones with me doing all the labour. I will pay someone to dig the holes for the footings though.

 

[FlaGman]

Are you concerned with the structure wanting to rack? It looks like it is designed to be attached to another structure rather than to be free standing.

 

[eljay]

Are you concerned with the structure wanting to rack? It looks like it is designed to be attached to another structure rather than to be free standing.

Yes, it is designed to be attached to a house, which is why I want to create this rigid aluminum offset ledger with its posts attached to the foundation wall.
The outer two posts will be on concrete footings poured below the frost line, so they won't move with the patio stones.

I think the offset crossbeam/ledger will be solid enough, so I can attach the patio roof to it.

 

[gregs]

The whole project? Way too much.
I'm expecting up to $15k including patio stones with me doing all the labour. I will pay someone to dig the holes for the footings though.

Not the whole project, just the structure. Thanks

 

[eljay]

Not the whole project, just the structure. Thanks

Well, the brackets and hardware should be around $300.
Each aluminum post ~$200 and crossbeam/ledger $400-$500, so around ~$1400. That's all Canuck dollars.
That's just for the ledger part.

Plus the cost of the above linked patio cover.

 

[CraigStu]

Why not just do 4 posts in the ground in concrete. 2 of them 2 inches from the side of the house. Figure out the roof height based on your siding so you can slip flashing under the bottom edge of a siding panel and attach it only to the new structure.

 

[eljay]

Why not just do 4 posts in the ground in concrete. 2 of them 2 inches from the side of the house. Figure out the roof height based on your siding so you can slip flashing under the bottom edge of a siding panel and attach it only to the new structure.

Do you mean lumber 6x6 posts? I really want to stick with aluminum to never worry about the posts down the road.
But yes, two 6x6 posts in concrete with a beam across would be half-price.

I wonder if I can get away with just two aluminum posts, but I thought I'd add the 3rd middle one to provide extra snow load capacity on the rear.
Would two of those deck brackets anchored with four 1/2" thick Tapcons provide sufficient load bearing? I know this is an engineering question.
Here's the strength data for 1/2" Tapcons: https://images.thdstatic.com/catalog/pdfImages/2d/2dc7e424-035d-495f-bdca-451ce7730fe4.pdf
The shear rating is 11,960 lbs, so at 4:1 safety factor, that's ~3000 lbs per fastener, so those aren't the limiting factor.
The brackets are rated for 1160 lbf max vertical load.
Each 10' aluminum post (4x1", 0.125" thickness) is ~110 lbs and the crossbeam would be ~190 lbs. So, with two posts it's 410 lbs just in that beam structure plus the patio cover plus any snow load. That's why I was thinking of adding a third in the middle.

But if you mean these two aluminum posts anchored/bolted to concrete footings near the house, perhaps that's a better way. Then the bracket/anchor strength is a non-issue.

 

[gregs]

Well, the brackets and hardware should be around $300.
Each aluminum post ~$200 and crossbeam/ledger $400-$500, so around ~$1400. That's all Canuck dollars.
That's just for the ledger part.

Plus the cost of the above linked patio cover.

I am asking about the patio cover itself. I do not see any pricing on the website you linked.

 

[eljay]

I am asking about the patio cover itself. I do not see any pricing on the website you linked.

Ah OK.
On their website, you can follow the links to various retailers. Home Depot sells them, for example.

 

[CraigStu]

.....
But if you mean these two aluminum posts anchored/bolted to concrete footings near the house, perhaps that's a better way. Then the bracket/anchor strength is a non-issue.

That is what I was thinking. You will have the tools etc needed to set the outers in concrete so just do two or three more. So now there is no strength issue to consider at all. If you weren't already planning on setting the outers in concrete it would be different but, once you are ready to go, doing a few more is not much extra work.

 

[eljay]

That is what I was thinking. You will have the tools etc needed to set the outers in concrete so just do two or three more. So now there is no strength issue to consider at all. If you weren't already planning on setting the outers in concrete it would be different but, once you are ready to go, doing a few more is not much extra work.

I am now considering going with screw piles for the outer footings. They cost a little more, but would cause minimal disruption to my existing pavers where I want to set one of the outer posts. The other footing will go into lawn.

I am not sure I'd trust a co crete footing being so close to the foundation wall and not shift away from it with frost cycles. But a screw pile may work instead, correct? I'll consult someone who deals with them, but perhaps I can get away with two screw piles near the house for the rear posts and a beam to tie them across. I believe they are about 8" wide at the bottom and they should be able to put them within right next to the foundation wall, so the post would be 2-3" closer to the house.

 

[CraigStu]

One thing to I just thought of to check on, are there drain tiles next to your foundation? You don't want to destroy them.

 

[eljay]

One thing to I just thought of to check on, are there drain tiles next to your foundation? You don't want to destroy them.

Good point!
Our house is slab on grade without basement, but yes, I wouldn't want to mess with anything near the foundation wall.

 

[PCustoms]

I stopped reading after you said you didn't want to attach it to the house, but the posted a bracket to attach it to the house.

"Maine deck bracket" WTF, never seen that hunk of I-beam in my life....

 

[eljay]

Good point!

One thing to I just thought of to check on, are there drain tiles next to your foundation? You don't want to destroy them.

Our house is slab on grade without basement, but yes, I wouldn't want to mess with anything near the foundation wall.

This is my foundation wall. So, standard 4-ft on a footing. I don't see any drain tiles being installed there when I took these pictures.
However, due to the footing protrusion, it looks like screw pile near the wall will not work as it would hit the footing or it would have to be installed too far away from the house for my liking.

So, currently, I am settling on this:
- Two outer posts on screw piles
- Two (instead of three) brackets attached to foundation wall with vertical aluminum 4x2" posts with an aluminum beam across to serve as the ledger for the patio cover.