How to get a post plumb using a bolt down anchor?

[mh]

I want to place some posts on existing concrete using Pryda bolt-down post anchors. https://www.bunnings.com.au/pryda-post-anchor-bolt-down-w-washer-100mm-m10_p1070068 The concrete is slightly sloped but the post needs to be plumb. What is the best way to get it plumb? I have done a similar job in the past just using window spacers under the plate, but that was just for a freestanding screen, nothing weight bearing. I want to do it a bit more professionally this time. Thanks. 

Is there a better way to get it plumb?

[MitchellMc]

Welcome to the Bunnings Workshop community @mh. It's great to have you join us and many thanks for your question.

I've made contact with Pryda in regards to your question. Since this is a weight-bearing application in order for the post support to function correctly shimming is not an option. You'll need to lay a level bed of structural grout for the post anchor to sit on.

Please let me know if you need further information or had questions.

Mitchell

[mh]

Thanks very much @MitchellMc. Sounds like a good solution that would also look good.

Would you lay the grout first before attaching the bolt down anchor, or put the anchor in first with gaps underneath and pour the grout to fill the gap? 

[MitchellMc]

@mh,

Forming up a pad, poring and waiting for the grout to fully cure would the correct method. My concern with pouring the grout underneath the anchor is that you won't be able to tell if there are any air gaps and if the post is fully supported.

Mitchell

[mh]

Thanks @MitchellMc .

Sorry for the string of questions... is it OK to drill a hole for the dynabolt right through the grout pad and into the concrete in one go? Without weakening the grout? Or does the dynabolt need to be already in position before the grout goes down?

[MitchellMc]

@mh,

Strings of questions are perfectly fine. We're here to help.

You can drill through the grout pad once it has fully cured. If the pad is 10mm or less you might have some cracking issues. I don't see any reason why you couldn't pre-drill the concrete and have the Dynoabolt in position prior to pouring the grout. You might want to run a piece of masking tape around the Dynabolt before inserting to stop the grout getting into the threads of the bolt.

Mitchell

[SMOKOTIME]

Hi Mitchell,

Just saw this and had to comment.  The whole idea of structural grout is that it expands in it's plastic state as curing to apply tension and fill voids.

Laying a bed of grout and letting it cure to set a post onto is counterproductive for the product.

The feet should be set onto a spacer and the grout packed underneath.  It achieves it's preload as it cures.

I use a single 1/2in gal nut in the center of the foot.  That gives sufficient gap to pack the grout and allows the post to be leveled on the four chemical anchors.  Once the post is plumb pack the grout in with a stick and finish the edges with a small trowel.  After 7 days when the grout has reached full strength tension all nuts again.

[MitchellMc]

Welcome to the Bunnings Workshop community @SMOKOTIME. It's fantastic to have you join us and many thanks for adding to the conversation.

The advice I've given above was directly relayed from a post support manufacturer's technical assistance team. They are specific requirements for the installation of their post supports on a structural grout base. It was advised that they do not recommend the method you've suggested of packing in the grout when the support is being used in weight-bearing applications. However, they were happy for your method being used in non-weight-bearing applications.

Many thanks for contributing.

Mitchell

[SMOKOTIME]

Really???

Not what their technical data says.

That is specifically how the product MUST be used for load bearing applications.

"Designed to undergo controlled expansion in the plastic state, it will ensure positive and
load transfer in structural grouting application. Lanko 702 Durabed has been formulated
to achieve high early strengths with low water addition levels."

Compressive Strength
MPa

Dry Pack  40.7 61.2 70.1
Plastic  25.4 48.6 51.7
Flowable  16.4 36.8 39.8  (What you would use to make a pad.)

Application Techniques
1. Lanko 702 Durabed should be placed within 20 minutes of
mixing to gain the benefit of plastic expansion. During
that time keep material in mixer well agitated. After this
time discard any grout mix that shows signs of stiffening.
2. Flowable Lanko 702 Durabed may be placed with lowpressure cement grouting equipment or may be hand rodded
into restrained sections. High points must be adequately
vented to allow entrapped air to escape.
3. Plastic Lanko 702 Durabed mortar may be rodded into place
or trowel handled where freedom of movement permits.
Consistency can range from thick cream to smooth plastic.
4. Do not vibrate Lanko 702 Durabed into position as this may
cause segregation of the mix.
5. Dry pack Lanko 702 Durabed mortar must be firmly pressed
or rammed into place. Consistency should allow pressuring
into a firm hard ball without cracking.
6. For sealing rebar or steel rods and bolts into bore holes,
adhere to the following guidelines.
7. Lanko 702 Durabed may be pumped for large grouting
installations.
8. All applications require curing. Cover the installed grout with
wet hessian sheets or spray periodically with water.
9. Placing Lanko 702 Durabed in unrestrained environments
will result in lower final compressive and flexural strength.

Kinda means that unless it is under pressure while curing the structural strength is significantly reduced.

[MitchellMc]

Hi @SMOKOTIME,

Many thanks for the additional information. Davco has advised that Lanko 702 is suitable to be laid as a pad and then to have the post support fixed on top of it as per Pryda's specifications.

Mitchell