# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  Fixing pergola post stirrups to existing slab

## Ash-g

Hi all,
I have just had a new pergola slab poured with the surface as "stamped concrete" to match existing
It was easier to have the stamping done without the stirrups set in.
The pergola will be fully braced as it will have two sides fixed to the house frame so there will be no movement in the pergola frame.
I am cutting back the eves to the top plate and running the pergola rafters up onto a pole plate or ontop of the top plate (not sure yet), then sealing the tile roof to the metal patio roof via a transition flashing.
I had the pergola slab poured with a 300x300 reinforced thickened edge.
I now want to fix the stirrups to this existing slab.
The stirrups will be the hidden / blade style.
Rather than anchoring them with dynabolts, I kinda didnt like the idea of an expanding bolt putting outward pressure near the edge of the slab, so will chemset threaded rods be a better/stronger option? or is there another way.
cheers  :Smilie:

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## METRIX

Depending on how close you go to the edge of the slab, Dyna's should not be a problem, I would recommend Stainless ones for long lasting, and use 125mm ones for your circumstance this way the dyna is well into the concrete and minimizes any concerns you have for cracking, remember to clean the hole out of dust before putting it in, or it will get stuck going down, and you will have a hard time getting it out 
We Dyna bottom plates down at every job, M12 Dyna's around 70mm in from edge and have not cracked a slab yet, Pergolas around 100mm from edge and also no problem. 
Saying that I have seen some posts on here of people using Red plugs and nails and blowing the slab edge off ?, maybe it's the mix they used was sub standard ? 
Concrete is a very sturdy substance, and it will take a lot more than one or two dyna's to crack it.

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## Ash-g

Thanks for the reply. 
Which ever way I was going to do it I was going to come in from the edges about 100mm as I need to dodge the reo when I drill. I took a photo of my tape measure up against the boards and over the reo before we poured so I knew its exact location in the slab.
Will definitely use stainless.
thanks again  :Smilie:

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## stevoh741

chemset or anchor screws much better option than dyna bolts. Chemset is cheap as nowadays and will give tons more holding power than a dynabolt and no risk of cracking anything.

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## cherub65

Chemset +1

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## ringtail

+ 2

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## Ash-g

.....hmmm I think I do still have a full tube of chemset left in the shed  
cheers   :2thumbsup:

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## Ash-g

Would stainless steel threaded rod chemset into slab react with HDG post stirrups ?

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## METRIX



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## Ash-g

Hmmmmm thanks for that.
I wonder if I'd get away with it  by using a good coating of insulation like duralac.

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## stevoh741

> Hmmmmm thanks for that.
> I wonder if I'd get away with it  by using a good coating of insulation like duralac.

  
Or you could just use gal chemset studs???? Don't use threaded rod it can screw out of the chemset, use the proper studs for chemset.

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## Ash-g

Didn't know that was an option. Thanks I'll check em out.

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## ringtail

> Or you could just use gal chemset studs???? Don't use threaded rod it can screw out of the chemset, use the proper studs for chemset.

  
Had this discussion just the other day with my supplier. I'm building a deck on top of a slab and went get all the chemset gear, studs etc... If using the chemical in the cartridge like 101 or similar the studs that I was given are just threaded high tensile rod. For the glass capsule chemical the studs are different. The have a hex drive on the top so you can use a drill to spin the stud and mix the chemical. Even then they are just threaded rod with a chisel end to beak the glass and mix the chemical.

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## ScroozAdmin

> Even then they are just threaded rod with a chisel end to beak the glass and mix the chemical.

  Just to clarify, the chisel end is designed to lock the stud in position and should be on either hex drive or flat headed studs. Hex drives are indeed designed for spin in systems like glass capsules and foil bags, although cartridge systems have taken a lerge part of the market in recent years as they are more forgiving to use and less susceptible to installer error. 
Incidentally it's not wise to use polyester based resins like chemset 101, powers ac100 in concrete due to long term shrinkage problems and poor chemical resistance to modern additives, more info here if your interested Kemfast chemical anchoring

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## Ash-g

> it's not wise to use polyester based resins like chemset 101, powers ac100 in concrete

  Thats how tie down rods are set in slabs in allmost every new house frame built today, which would be to Australian standards yes?

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## ringtail

That kemfast looks absolutely identical to the product that I now use which is fischer FIS P 300 T - same ingredients too reading the MSDS

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## Ash-g

is the kemfast or fischer FIS P 300 T available over the counter in a retail store or only online?

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## ringtail

> is the kemfast or fischer FIS P 300 T available over the counter in a retail store or only online?

  I just get it from my timber supplier as thats what they stock apart from 101 and the glass tube chemset. I havent noticed if bunnings sell the fischer. I pay $ 23 at trade level for the fischer so if bunnings do sell it I'd expect to pay around $  28 - 30 retail.   fischer fixing systems   
give them a call and ask for your nearest distributor

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## Ash-g

went with 100mm galvanized ramset ankascrews.
easy as, no mess, neat finish, job done, very happy  :Biggrin:

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