Pergola Footings Under Existing Patio

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amdaman

6 posts

Wannabe Geek

#298583 29-Jun-2022 12:37

Hi,

I'm wanting to place an aluminium pergola on my existing patio but I want the footings to be securely anchored (as you'd expect). I've been having a hard time finding a tradie to do this so I've been thinking about giving it a go but need some expert advice on the sequence and any best practises.

So currently the patio is made up of concrete pavers that are around 40mm thick and they appear to be resting on a 20mm-ish cement or concrete base with a compacted fill under that. The joints are made up of polymeric sand.

My goal is to lift 6 pavers, dig down 10cm on each, fill with concrete and then cement and lay the pavers back on top. The footings will be tied down with 80mm stainless steel anchor bolts (through the pavers)

I've got some questions though;

What is the best way to list each paver without damaging them?
After the paver is lifted what is the best way to remove the existing concrete/cement they are laid on? Is this just a pneumatic drill or a grinder to cut the square required?
Once the concrete has set what is the best way to lay the pavers back on top? Just regular cement or mortar and level off with a spirit level?
Will there be any issues putting the new polymeric sand back in the joints where it meets old polymeric sat that has been set for some time?

As you can see, I have no idea so any help appreciated! Pics below.

Thanks!

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2391 posts

Uber Geek

#2935968 29-Jun-2022 14:23

it depends a bit on how big it will be and if you want it covered at some point.

i would be inclined to simply put posts down in the gravel areas. i think if you bolt through the pavers you run the risk of them cracking later on. better to cut the paver to go around the post.

johno1234

2804 posts

Uber Geek

#2935969 29-Jun-2022 14:27

Does the pergola have a roof? If not, and if those pavers are as heavy as they look then perhaps the whole thing has such a small wind load that the pergola feet could simply be screwed to the pavers with concrete screws - that's if the pergola feet have flanges that can be bolted down.

If it has a roof, or a slatted roof and catches a bit of wind, then I would consider putting a concrete pad underneath as you suggest, but you'll need some really long masonry anchors so they don't expand within the pavers and crack them.

Or, you could simply lift the paver, excavate 100mm and fill with concrete, float it off, edge it nicely so it looks somewhat like the other pavers just much deeper and heavier. Then you can just masonry screw or anchor directly into it.

I will watch with interest as I will have a basically identical project in a month or three. Installing one of those DIY slatted roof pergolas over pavers.

[ADD] Make sure your pads are perfectly level or it will be a pain getting your pergola to sit nicely. If they aren't, shim under the feet until they are. A laser level will be handy for this.

amdaman

6 posts

Wannabe Geek

#2935971 29-Jun-2022 14:29

The pergola is 8x3m which is pretty much the length and width of the existing patio. It's an aluminum lourve type so I'm pretty limited there sadly.

johno1234

2804 posts

Uber Geek

#2935973 29-Jun-2022 14:31

amdaman: The pergola is 8x3m which is pretty much the length and width of the existing patio. It's an aluminum lourve type so I'm pretty limited there sadly.

I have similar issues. Has to fit under the eaves, and there's a concrete step in the way on one corner...

mattwnz

20155 posts

Uber Geek

#2936062 29-Jun-2022 16:57

I suspect your footings are going to need to be a lot deeper than that. I think NZS3604 maybe of help.

amdaman

6 posts

Wannabe Geek

#2936078 29-Jun-2022 18:20

Johno, I had that issue as well. I got a local engineering firm to cur the legs down by 20cm or so, wasn't that expensive and meant I could keep the pergola within the patio area.

Digging the footing deeper isn't a problem, it's the rest of the process I'm seeking advice on.

Cheers

Jase2985

13461 posts

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#2936081 29-Jun-2022 18:27

mattwnz:

I suspect your footings are going to need to be a lot deeper than that. I think NZS3604 maybe of help.

This^^

what you are proposing is woefully inadequate

here is the connection recommendations for a louverkit louver leg. 800mm deep and 600mm square or diameter.

https://www.louvrekit.co.nz/Content/Images/uploaded/Product%20Docs/Post%20To%20Concrete%20Footing%20Connection.pdf

On a flat concrete surface they recommend 100mm minimum with reinforcing steel and 1.5x1.5m under each leg.

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amdaman

6 posts

Wannabe Geek

#2936083 29-Jun-2022 18:34

Is that a recommendation or a requirement? Making the footings deeper isn't an issue but I won't be going to that extent in a low wind zone in a sheltered location.. Most people install these on a wooden deck.

Jase2985

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#2936084 29-Jun-2022 18:41

amdaman: Is that a recommendation or a requirement? Making the footings deeper isn't an issue but I won't be going to that extent in a low wind zone in a sheltered location.. Most people install these on a wooden deck.

Recommendations based on the building code

do most people do it properly though?

they also list the upgrades needed for a normal wooden deck.

My 5x3m louver is bolted to 125-150mm rebar reinforced concrete.

amdaman

6 posts

Wannabe Geek

#2936097 29-Jun-2022 18:55

Jase2985:

Recommendations based on the building code

do most people do it properly though?

they also list the upgrades needed for a normal wooden deck.

My 5x3m louver is bolted to 125-150mm rebar reinforced concrete.

Do most people do it properly? I'm not too sure but these kits seem to be marketed to the average DIYer so I don't think many would they would be putting an 800x600 rebar reinforced footing down for each post. No one i've spoken to has done it that way, it's either been on a concrete patio or on a wooden deck but I can see why the code would recommend it, especially in high wind zones or if you accidentally leave the louvres closed.

I'll certainly make the footings deeper based on this convo, it's the other bits of the process i'm after advice on though.

Jase2985

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#2936104 29-Jun-2022 19:21

The kits that are sold by the likes of container door etc yes marketed at the average person with no consideration over proper mounting etc. tell you to get a tradie to do it.

will you be cutting the pavers to go around the posts?

i honestly think you would be better pulling all the paving out and putting down a concrete patio.

jonherries

1395 posts

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#2936113 29-Jun-2022 20:04

Yep i have 400x400 x700 deep concrete reinforced piles for my posts due to uplift potential.

Did it myself last christmas, but it is made from laminated timber rather than aluminium with a clear polycarbonate roof that match the rafters.

Jon

johno1234

2804 posts

Uber Geek

#2936187 29-Jun-2022 21:18

The key is the roof. These alu pergolas are light and if open have negligible wind load or lift. If they have a roof it’s a whole different story.

mattwnz

20155 posts

Uber Geek

#2936188 29-Jun-2022 21:19

Not only wind uplift, but the columns maybe acting as the resistance against lateral loads. It all depends on the instructions and how it has been engineered. Some councils may need a consent especially if it is with a certain distance from the boundary. So I would check with the council. Sine have restrictions on structures in setbacks. We needed a consent for a small shed because it was close to the boundary.

nickb800

2716 posts

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#2936287 30-Jun-2022 06:33

I'd say position the posts into the corner of the pavers if possible, that way it's a simple job of two cuts from an angle grinder with a masonry disc.

I think you should be able to lift the pavers with a club hammer and cold chisel from the side.

Dig out your footing, add rebar and threaded bolt, then pour concrete, set the paver back on concrete, fill the cutout with concrete flush to the surface. That way the posts bear on concrete, not paver - less chance of cracking.

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