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How to create the concrete footings using embedded post anchors for an arbour?

BeginnerPaul

Good Evening Folks

I would like to construct a small arbour say 2metres by 3 metres and 2 metres high. Posts say 90x90

This question is about creating the right footings for the post anchors

Am considering post anchors which will be embedded in concrete

Pryda 200 x 90mm M10 Full Stirrup Solid Stem Post ...$16.31Add to Cart

Question is what are the right dimensions for the concreted hole which will have the post holders embedded

All advice welcome

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Comments

JacobZ

Hi @BeginnerPaul,

Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.

While it is fairly unlikely you'd require building approval, I'd suggest you start by contacting your local council to confirm this. Rules vary from region to region, and it is always better to be safe than sorry. A quick phone call to confirm this can save you a lot of pain further down the line.

It is hard to give definitive answers to this question as structures like arbours are subject to a number of variables that can alter footing design greatly depending on things like the wind rating of the area and the soil quality. If you want a definitive answer, you will need to contact an engineer for their assistance in designing a suitable footing. They will be able to use the Pryda Post Anchor Design Guide to design footings that are suitable for your arbour.

With this being said, footings that use post anchors are generally 300mm in diameter and at least 600mm deep. I would suggest using a high wind anchor such as this Pryda Post Anchor High Wind 450 x 90mm M12 as opposed to the one you've linked to above.

Footings can be dug with a Post Hole Digger which has a 300mm auger that is designed for this exact purpose.

Let me know if you have any further questions.

Jacob

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/42506#Comment_42506

Thank you JacobZ

The Arbour will be small - say 2m x 3 m.

Ideas on how to align the 4 posts properly?

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/83473#Comment_83473

Hi @BeginnerPaul,

Setting everything out before the project commences is the best way to make sure everything aligns.

Have a look at How To Set Out A Deck for some guidance on setting out your project.

Start by selecting the post that is most important in terms of alignment. There may be a garden bed or fence line that you can measure off to ensure it is placed correctly. Working from this point, you can mark out the general area with marking paint.

You can then construct hurdles from scrap timber and star pickets. These should be low enough to the ground that string lines will run right by the anchors when they are set in the concrete.

You should then use the 3-4-5 method to ensure the string lines are perfectly square to each other. Measure everything 2-3 times and make small adjustments where necessary.

If you need your anchors to be level with each other, you can use a Line Level, making slight adjustments to the height of your hurdles to get everything nice and level. This step is not 100% necessary as you can always cut the top of your posts instead of having the bottom of them perfectly level.

You can then use How To Install Stumps as a guide for installing your anchors. You should use a torpedo level to ensure your anchors are plumb when they are installed.

Plumbing the anchor will make sure they are plumb in one direction, but as the anchors have an open and closed side, you will still need to check for plumb when installing the posts.

After the posts are installed, checking for plumb, level and the distance between posts as you move higher into the construction will ensure everything is aligned at the top of the posts as well as at the bottom. With each new addition to the structure, measure distances between posts and check for plumb and level.

Let me know if you have any further questions.

Jacob

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/106654#Comment_106654

Thank you JacobZ

The small arbour 2m x 3m is of simple design

Are there videos which would be useful?

Regards

Paul

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/120521#Comment_120521

Hi @BeginnerPaul,

How To Build a D.I.Y. Timber Garden Arbour has a video that should come in handy, but it is not exactly the same size as the one you have planned.

The video in How To Install Posts For a Picket Fence would also be handy for some guidance on setting your posts and anchors.

Also, alot of the principles used to build a deck would come in handy for your project. There are a number of videos in How To Build A Deck that would be useful.

I am sure if you have a look on Youtube you will be able to find similar projects that you can follow along for guidance.

Also, remember the Workshop community will always be here to help if you run into specific questions along the way.

Jacob

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/129083#Comment_129083

Thanks JacobZ. That has been very useful.

Questions now about fixing the 3m long bearers (150 x 50) to the 90 x 90 posts:

Are coach screws the most appropriate?

What size coach screw is right to connect the two pieces?

1 or 2 at each end?

How to use a power drill to drive the coach screws?

Thanks

Paul

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/134515#Comment_134515

Hi @BeginnerPaul,

Coach screws or cuphead bolts can be used. Using bolts would be the best option as they provide significant compression to the joint.

These ZENITH M10 x 150mm Hot Dip Galvanised Cup Head Bolts & Nuts would be sufficient for the 50mm bearer and 90mm posts thickness.

I would suggest two at each end.

With your power drill, you'll drill a 12mm hole through the bearer and post. Then, you insert the bolts, washer, and nut before tightening them with a spanner.

I just wanted to point out that 3000mm is fairly long for 140 x 45mm to span. You should check timber span tables to ensure it is of an appropriate calibre for your project.

Please let me know if you have any questions.

Mitchell

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/137998#Comment_137998

Thank you Mitchell for your advice

I could have mentioned that two bearers are planned on either side of each post

For bolts that would be a total depth of 50mm plus 150mm post and 50 mm say 250 Wonder what size bolts would be appropriate?

Where would I find a relevant timber span table please?

Regards

Paul

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/140382#Comment_140382

These ZENITH M16 x 260mm Hot Dip Galvanised Cup Head Bolts & Nuts should do the job @BeginnerPaul.

Mitchell

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/142096#Comment_142096

Thanks Mitchell

To recap:
I would like to construct, DIY, a simple arbour/pergola It will be free standing, have no roof, just bearers and 'cross pieces' every 50cms then with very thin 'rafters' all to support plant vines.
3 metres by 2 metres by 2.2 m high using inground Pryda post anchors keeping the posts clear of the ground.

Posts, currently planned as (88X88); 3 metre bearers (138x42); 'cross pieces' questio0n below; thin rafters' (42x18) say 6 x 3 metres.

Understand that the length of bearers will be fine as the "cross pieces" will add strength.

Using to join the posts and bearers - bolts and nuts as advised

Advice would be appreciated on:

Questions are: # size of "cross pieces" planned every 50cm (138x42. OR smaller if practical??

#these cross pieces will be recessed to sit onto the bearers but I guess will need additional attaching #?best done with some hangers or screws or both?

#What size timber for braces at corners? # Do they need to be as big as the bearers or cross pieces?

#Can I buy Design Pine from Bunnings -special orders?

Thanks for your assistance

Rough plan photo below

What size braces (2 at each corner) 138x42 OR smaller 90x42?? what to use to fix the braces - coach screws , wood screws, smaller bolts and nuts?
The cross pieces will be recessed to sit onto the bearers but I presume will need additional fixing - would some style of hanger be right OR screws?
Where to buy the recommended Tanalised EnSeal for cut ends and Design Pine primer
In anticipation, thank you for your assistance
regards

Paul

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/143326#Comment_143326

With the cross pieces, they have to be able to span the distance unsupported @BeginnerPaul. Provided its the 2000mm span, 140 x 45mm should be fine, but you couldn't go down to 90 x 45mm as it would bow over that distance.

If you are notching the cross pieces then you can screw through the top of them down into the beam. Joist hangers certainly would hurt, but your aesthetics might take a hit.

Braces at the corners could be done with 90 x 45mm.

We can order Design Pine, and we also have Woodhouse laminated and primed Pine in store.

Braces could be fixed with coach screws, but my preference would be bugle batten screws.

Tanalised 300g Clear Enseal Timber Treatment is suitable for your cut ends.

Any exterior primer such as Dulux 1Step would be suitable.

Please let me know if you have any questions.

Mitchell

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/144239#Comment_144239

Thank you Mitchell

I appreciate your advice that Bugle Batten screws would be suitable for fixing the cross pieces to the beams/bearers. According to the plan Image, the cross pieces will be placed on their 42mm sides, and notched leaving say half of their 138mm depth available for screwing into the bearers' sides.

Question is what specifications (size, length/stainless steel) for those bugle batten screws?

I have tried to place a Special Order for the Design Pine timbers at Port Macquarie today and wait for the response from design Pine

The Bunning website has over 600 items when searching for the Woodhouse alternative but in most cases there does not seem to be a comparable product for the treated, DAR and primed items. Phone call did not assist.

Question: Any ideas on how to identify whether my size (DAR primed) timbers are available?

Question too about concrete: The inground post anchors have been ordered. How long after the anchor concrete footings have been mixed and put in place in their holes should I wait before installing the timber posts and the rest of the arbour construction?

Thanks

Paul

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/144913#Comment_144913

Hi @BeginnerPaul,

I'd advise using the Bremick XTP 14g x 150mm T40 Stainless Steel 316 Bugle Batten Screws down through your cross pieces into the bearers, with 1 in each bearer totalling 4 per cross piece. I'd advise using stainless purely because the screw head will be facing up and is likely to have water pooling on it. The slight increase in the cost of stainless fixings is justified by their ability to withstand rust when consistently wet.

Use a Sutton Tools 5.0mm Long Series Jobber Drill Bit to drill pilot holes as screws of this size and length will displace a lot of timber fibres causing bulging and splitting if pilot holes aren't drilled deep enough.

Woodhouse produces 88 x 88mm 2.4m H3 LOSP Posts, 138 x 42mm H3 Treated Pine Primed LOSP and 42 x 18mm 5.4m H3 LOSP which would all be suitable for your arbour.

With your concrete footings, I'd suggest a week of curing time before continuing construction. After 7 days, concrete typically reaches around 70-80% of its full strength, which will be enough to resist any forces applied to it during the construction process. This will allow you to pour concrete one weekend and then begin construction the next weekend.

Let me know if you have any further questions.

Jacob

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/145443#Comment_145443

Thank you Jacob

I am putting together all your advice and that from Mitchell. Do appreciate your assistance.

Latest questions are:

Post Anchors. - what specifications for the bolts and nuts for Pryda Post Anchor High Wind 450 x 90mm M12 ; how to choose the correct washers?

Posts to Bearers - what washers for the M16 x260 recommended bolts/nuts

Braces. - Plan to use bugle baton screws as recommended. Specifications please for screws as there re so many

Related Question: As the Braces will be screwed into the posts at 45degrees, would some screwing guide be useful?

Slats (3m parallel with bearers and across the cross pieces) - cross pieces will appear at ends and every 50cm along the about. They will be on their side. Purpose of the slats is to be the final timber to hold the climbing vines. Question is: how often to screw the thin slats into the cross pieces?

Related Question: what screws, spec, and stainless steel as will be facing up?

Timber Design Pine or Woodhouse: Is Woodhouse available at 90 x 42 4.8 metres for the braces? Is Woodhouse available at 42 x 18 6.0 metres for the Slats?

Thank you in anticipation

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/145855#Comment_145855

Hi @BeginnerPaul,

Thank you for the follow-up questions.

Post Anchors - I'd suggest these ZENITH M12 x 120mm Hot Dip Galvanised Hex Head Bolts and Nuts. There is no need to use a washer for this connection as the bolt head and nut will be tightening on the post anchor which will spread the load in the same way a washer would.

Posts to Bearers - I'd suggest using these ZENITH M16 Hot Dip Galvanised Flat Round Washers on the nut side only. This is because the cup head on these bolts is designed to spread the load in the same way a washer would.

Braces - You're aiming for the screw to be embedded at least halfway into the post. Depending on the angle of the brace, something 100mm long like these ZENITH 14G - 8 x 100mm Class 3 Galvanised Bugle Batten Screws will be fine.

I'm not aware of a jig that is adjustable to meet the angle of your braces. The trick to driving screws into angled surfaces is to predrill them first. Starting the drill bit perpendicular to your brace, drill a small hole roughly 5-10mm deep. You will then change the angle of the drill bit to run perpendicular to your post. The original 5-10mm hole will hold the drill bit in place stopping it from slipping down while you drill the pilot hole at your desired angle.

The thin slats should be screwed into every single batten. You can use Bremick 10G x 50mm Black Stainless Steel 304 T20 Trim Decking Screws. Looking at your picture, you will need 52 of these screws. This is the most cost-effective stainless-steel screw I could find that will give you enough screws.

Unfortunately, the 90x42 does not come at 4.8m, you will have to grab this 90 x 42mm 5.4m F7 H3 Treated Pine Primed LOSP.

Unfortunately, the 42 x 18mm 5.4m Moulding H3 Treated Pine FJ Primed 4 Edge Pencil Round LOSP only comes at 5.4m.

Let me know if you have any further questions.

Jacob

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/145443#Comment_145443

Thank you for your advice to use Bremick XTP 14g x 150mm T40 Stainless Steel 316 Bugle Batten Screws down through your cross pieces into the bearers

I see that there is a bit included

Question is:

Should I use my impact driver or my drill? If the impact driver, is an additional 'attachment' needed to house the supplied bit or can it go directly into the impact driver?

and Bremick 10G x 50mm Black Stainless Steel 304 T20 Trim Decking Screws. (which does NOT include a bit)

Advice please on which drill bit/impact attachment ?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/145859#Comment_145859

Hi @BeginnerPaul

I've had a bit of a read in regards to the Bremick Screws and there is no mention of using an impact driver on it. Just to be on the safe side, I suggest drilling pilot holes and using your ordinary drill to imbed the screw into the timber. In regards to the other screws, I suggest doing the same thing and that is to drill pilot holes and using your ordinary drill. As for the drill bits, I suggest using good quality ones like Kango HyperTorque™ TX30 50mm Impact Driver Bit. Please note that the Bremick decking screws use a T20 so make sure you get the correct size.

If you need further assistance, please let us know.

Eric

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/145859#Comment_145859

Hi @BeginnerPaul,

While both an impact driver and a drill can be used for drilling or driving, generally speaking, you would use a drill for drilling pilot holes and an impact driver to drive your screws into those pilot holes.

A drill will accept both drill bits and impact bits, whereas an impact driver will only accept impact bits.

An impact driver's chuck is designed to lock onto driver bits with hex-shaped shafts with a groove. See below for an example.

The Sutton Tools 5.0mm Long Series Jobber Drill Bit is the only bit that has been mentioned that can only go in your drill. This is because it has a smooth shaft that is not compatible with an impact driver's chuck.

As you've mentioned, it doesn't appear that the Bremick T20 Trim Decking Screws include a driver bit. This Kango 50mm Hypertorque Torx Mixed Impact Driver Bit contains a variety of Torx bits including a T20 bit, which is what these screws use. I'd suggest this is a good option for you.

For driving the Bremick T20 Trim Decking Screws, you can use either a drill or an impact driver, but personally, I would usually use an impact driver.

Let me know if you have any further questions.

Jacob

BeginnerPaul

https://www.workshop.bunnings.com.au/discussion/comment/146177#Comment_146177

Good Morning JacobZ

Thank you for your comprehensive advice and taking the time to include diagrams.

I will pre drill and then use impact driver as suggested

Bremick XTP 14g x 150mm T40 Stainless Steel 316 Bugle Batten Screws .

I see that there is a "bit" included

Question is: Will that be a 'driver bit' or do I need to buy a T40 'driver bit'

ZENITH 14G - 8 x 100mm Class 3 Galvanised Bugle Batten Screws.

Includes a "Driver bit TORX30" so NO Question here

Bremick 10G x 50mm Black Stainless Steel 304 T20 Trim Decking Screws. (which does NOT include a bit)

Will buy the suggested Kanga mixed pack of driver bits including a T20 bit however, is there a higher quality option?

More related Questions:

Will buying an extension for the impact driver - "hex Shank"?? - be useful? Could you recommend one please?

Do appreciate your interest

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/146443#Comment_146443

Hi @BeginnerPaul,

Yes, the bit included in your Bremick XTP 14g x 150mm T40 Stainless Steel 316 Bugle Batten Screws will be a driver bit.

There's not a huge amount of difference between driver bits, but these IRWIN 75mm T20 Magnetic Power Bits are good quality and magnetic so they should be a good option for you.

Extension bars such as this Kango Hypertorque 300mm Impact Extension Bar can be handy if you need to drive screws that are just out of reach, but realistically with your project, there is not much need. Moving your ladder and body so you are balanced and comfortable will driving screws is always better than using an extension bar.

Let me know if you have any further questions.

Jacob

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