# Forum Home Renovation Brickwork  mortar mix for brick piers

## emptybucketman

What's the usual mortar mix for 230x230 brick piers?  I see 6:1:1 Sand:cement:Lime is used for most brickwork above the damp course.

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## autogenous

Depending which state I think 230 x 230 piers are banned now.
Too many kids getting killed I think?
You will have to have a 10mm rod go from the footing right up the middle no matter what you do. 
Yeah 6:1:1 is fine.

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## emptybucketman

thanks Autogenous, 
I see in the book "Acceptable Standards of Domestic Construction" (little outdated) that for piers use class M3 Mortar Mixes 1:1:6.  I didn't know that 230x230 piers are on the way out and that tie down is mandatory.  Many thanks.

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## autogenous

> I didn't know that 230x230 piers are on the way out and that tie down is mandatory.  Many thanks.

  I think they have been banned in Western Australia for about 5 years? 
The rod up the centre has been mandatory for some time. Some times it has adverse effects because bricks have to be cut around the rod reducing the structural integrity of the pier. 
If the rod is bent or incorrectly positioned keeping in mind clients want accuracy within 5 mm the rod pushes the pier all over the place when being built. An absolute disaster. 
You can get screw in bolts to take rods so that the rod ends up more accurate in the 10mm gap allowed for the rod. The screw in bolts or fixings can be post fixed after the footing is poured. 
I think its because kids playing around on building sites etc were pushing them over and killing each other? 
Best to go a 350 x 350 pier and core fill it at least a metre. If there is a roof involved the rod ties in with the pier rod.

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## intertd6

Lime is not allowed below the damproof course as ground water with acid will eventually dissolve the lime in the mortar. If a tie down rod is needed from the footing to the bearer this can go beside the pier attached to the footing or cast in, then thru the bearer, this method saves any penetrations in the ant capping, 230mm square piers to a certain height are ok in NSW
inter

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## Make it work

I used the dry mixed baged stuff, it set nice and hard but was workable and easy enough to mix. It cost more than the mix your own option but for a small extension it worked out to be the convienent option for a slow bricklayer like me. 
As for 230 X 230 piers, there were no objections through council or with the certifier, I used a 10mm gal rod anchored into the pad and was told that it was only manditory because my house is clad. If it was brick veneer, no tie down was necessary.

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## autogenous

> Lime is not allowed below the damproof course as ground water with acid will eventually dissolve the lime in the mortar

  Obviously Sydney has some pretty heavy acid goin down in the soil.  
It must be a local regulation relative to state or council. Its due to acidic clays? 
I assume then if it is truly the case then you'll have to go 3 sand 1 GP cement below the damp course line. 
There is no requirement for this in Western Australia even less so in a pier. 
What does the damp course line consist of?
What is the specification for a damp course in Sydney? :Smilie:  
Acid reacts with lime but it also reacts to a lesser extent with cement. Cement is lime and clay mixed together. 
What makes me laugh is the introduction of fly ash into cements which has made cleaning of brickwork a lot harder usually resulting in the brick cleaner adding more acid with poor results. Hydrochloric acid appears to have lesser reaction with fly ash.

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## intertd6

"Obviously Sydney has some pretty heavy acid goin down in the soil."  
Most soils in australia are acidic, also being in a urban & industrial area acid rain is a factor  
"It must be a local regulation relative to state or council. Its due to acidic clays?"
This is a standard clause in nearly all building masonry specifications I have used. 
"I assume then if it is truly the case then you'll have to go 3 sand 1 GP cement below the damp course line."
1:3 is allowable for a mortar DPC, 1:6 raio is the norm with plastisizer 
"There is no requirement for this in Western Australia even less so in a pier."
The masonry standard does allow for small quantities of lime in M3 & M4 mortar (all exposures) mixes but because the brickies over here love to not use lime whenever they can (because it burns in cuts & eyes) the specs have gone in this direction 
"What does the damp course line consist of?"
Usually embossed plastic for cottages, some termite barriers can be used as DPC
"What is the specification for a damp course in Sydney? :Smilie: "
The same as WA, AS 2904 
"Acid reacts with lime but it also reacts to a lesser extent with cement. Cement is lime and clay mixed together."
True thats why the cement ratios are higher where they can be affected by acids  
regards inter

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## autogenous

>> Most soils in australia are acidic, also being in a urban & industrial area acid rain is a factor< 
A DPC isn't going to stop acid rain. Rising damp with acid sulphate soils maybe but if its that bad Id be more worried about the kids and the arsenic. 
All mortar in Western Australia is 6:1:1; there is no external DPC brickwork requirement; well there may soon be but not for acid. However that effects the egress of the moisture that exits the cavity weep holes to the building. 
>> 1:3 is allowable for a mortar DPC, 1:6 raio is the norm with plasticiser< 
If plasticiser is used, mortar should be 1:4 even 1:3 to keep the matrix to aggregate ratio up.
Adding an aeration agent with a 1cement :6 sand mix is a recipe for disaster.  
Cement is susceptible to acid break down, If you wish to stop acid ingress via capillary action into brickwork then a PV flashing needs to be laid. 
Laying PV flashing into a free standing pier especially without a starter bar would be a disaster. The pier is highly susceptible to being pushed or blown over. 
The liquid DPC additive works best with a pure cement ratio of 3s:1CGP however a matrix aggregate ratio of 6 sand to 1 cement and 1 lime in any ratio as long as the aggregate matrix ratio is 3:1 produces the results. 
Its nearly waterproof on its own let alone the DPC liquid additive. 
The issue in many cases is the DPC liquid is mixed with a sand/cement above 3:1 say 6:1 add a plasticiser aeration agent that puts bubbles into the mud and its a pointless exercise. 
I guess; when in Rome

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## intertd6

DPC is a requirement as per the Standard in any state or territory, in good building practice it is situated 2 courses above finished ground level, not on piers the ant cap is the DPC
DPC will stop the upward movement of acid rich moisture & prevent the common problems of efforesence, rising damp, wet walls & contact with the lower exposure mortar above it
Construction is not allowed on acid sulfphate areas here with out preventative measures being taken
As said before most building specs ( Govt & commercial ) here now just exclude lime from below DPC level & that sometimes means 2 separate mixers going on a gang
Inter

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## autogenous

> As said before most building specs ( Govt & commercial ) here now just exclude lime from below DPC level & that sometimes means 2 separate mixers going on a gang
> Inter

  And this is to the external cavity wall in particular?  
So they must be laying 2 or 3 external course with 3 sand 1 GP cement mortar without plasticiser. 
Ouch
It would go off in a second be hungry as hell and the cement would pull the wall as it dries.  
Once the mortar hits about 42 mpa its water proof anyrate. 
Any salts or vanadium carried by the water down the outside skin (which a lot of it comes from) will leave a white or brown ring above the DPC line. 
More moisture goes down than capillaries up. 
The mortar whether it be creme or grey will be tremendously two different colours.  
I've seen buildings built out of 3:1. You build the corner then come back and the mortar pulls the corner out of plumb. 
Id be more inclined at putting in a physical barrier at -2 or -3c on the footing. Probably bitumen emulsion or resin sprayed on the footing then back up the slab edge.
Termites aren't big fans of it. 
Sounds like an old British standard DPC detail where there lots of water and plenty of clay occurs. 
I guess NSW and other places with high clays soils suffer the same situation any rate. 
Liquid DPC has only a life span of about 20-25 years. Not quite a 100 year government requirement. 
Maybe some methyl cellulose in the DPC course mortar would help? 
Mortar stronger than bricks though, ouch. 
Its a standard so its compulsory.

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## intertd6

No 3:1 mixes just 6:1 with fire clay to fatten it up & air entraining admixture
Inter

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