Dear Bunnings Community,
I would like to hear your advise on fixing my leaning fence. My fence is leaning towards the footpath due to the storm last year. The posts are on higher ground than the retaining walls outside of the property. The retaining are attached to the posts at the bottom. Half of the posts are rotted at the bottom and really weak. Half of the posts are fine for now. For the posts that are strong enough, I am planning to use two of Simpson Strong-Tie 90mm Fence Post Repair and Reinforcement E-Z Mender to reinforce the posts. For the weak posts, I am planning to dig out the footing of the posts completely and replace the footings with something else, such as concrete spurs ( I am not sure they are available in North Brisbane). Can you please advise if my solution will work, or I will be better to replace the whole posts, from top to the bottom? Also, If I do it myself, what is the complexity of the job? What should I pay attention to? I have basic knowledge of working with tools and landscaping.
Hi @ThomasBNE,
Your tools look good and will work.
There is no need to remove all of the palings, but you may need to remove one or two directly in line with the post so you can drive screws through the rail into your new post.
Your fence will naturally lean at the top of the posts, so when setting the posts in place, make sure the bottom of the post is tight to the bottom rail and then roughly plumb the post in both directions, ie. forward, back and left, right. At this stage, do not attach the rails to the post. You are going to brace the post so that it stays plumb in both directions while the concrete sets then attach the fence rails once the concrete has set with the post plumb.
You will brace the post by driving a short picket into the ground, screwing a piece of timber to it, then running it at a 45-degree angle to the post, then screwing or clamping it to the post. It will look like this -
After 24 hours drying time, you can screw the rails to the new post, reattach the palings and then remove the braces.
Let me know if you have any further questions.
Jacob
Welcome to the Bunnings Workshop community, it is fantastic to have you with us.
You are thinking along the right lines, but there are a few structural realities with fences and retaining walls that are worth being very clear about before you commit time and money.
Because your retaining wall is fixed to the fence posts, those posts are doing two jobs. They are both supporting the fence and resisting the lateral soil load. Once posts start rotting at ground level, their load bearing capacity drops very quickly and if the post is rotting below the soil line, then it is doing very little to hold the retaining wall in place.
Using Simpson Strong Tie E Z Menders would be a good option if the posts were not doing two jobs, however as they are, I would not recommend them as they will do very little to support the retaining wall.
Concrete spurs are also not a great option because they are attached to the post above ground, so they are doing very little to support the retaining wall beneath it.
Ideally, the posts should not be used to support both the retaining wall and the fence, however due to your circumstances, there is very little you can do to rectify this issue without complete removal and reinstatement of both with alternating post locations. If you wanted to shore up the fence and retaining wall long term, this is what I would recommend, but ultimately, this is a lot of work that would come at great expense.
I think the best thing you can do is systematically work your way along the fence replacing the damaged posts one at a time. You will have to start by supporting the fence on either side of the post you are working on. This can be done by driving a 240cm Ultrapost into the ground on either side of the post, then screwing the fence rails to it. Once this support is in place, you can use something like a jackhammer or rotary hammer drill alongside a fencing bar to break up and dig out the concrete post foundation.
Once the post you are working on is out, you should apply 2 coats of bitumen membrane to the underground portion of your new post. This will help to prevent water from getting into the post and rotting it out again.
While installing the post, you'll want to reattach the timber sleepers and fence rails to the post, then concrete the post in place, bracing it so that it is plumb. Check out How to Set a Post for some guidance on this process.
Once you have repaired one post and the concrete has set, you can remove the supports and move on to the next post.
It is going to be a fair bit of work, but because of that retaining wall, I think it is the best option.
Let me know what you think and if you have any thoughts or concerns, please let me know so I can assist further.
Thank you @Jacob for answering my question. I was thinking in the same line of working one post at the time. Do you know who far from the old post I should install the Jack 240cm Black Premium Ultrapost? Will I just hammer the ultrapost into the ground or will I need to use something else to secure the ultrapost? Also, can I use the https://www.bunnings.com.au/full-boar-1050w-7kg-sds-max-demolition-hammer-kit_p0094370 to break out the concrete footings? Do I need to use bitumen menbrance paint if I use galvanised steel posts 75mmx75mm? Thanks.
When I've done the same with Ultraposts, I installed them around 600mm away from the post on either side. This seemed to work well and I imagine would be the same in your situation. You would install them with a hammer, ensuring that you drive them a good distance into the soil, preferably around 600mm, hence the use of the long posts. Once they are in place, use some hex head timber screws to fix them to the fence rails temporarily.
Yes, the Full Boar SDS Max Demolition Hammer should work fine.
If you are using galvanised steel posts, then there would be no need for the bitumen membrane as the galvanising will protect the posts. In saying this, any drilling through the posts will remove the galvanisation, so you should apply some Cold Gal Spray Paint to your bolt or screw holes to protect them from rust.
Thank you @JacobZ for helping me out.
If I have 10 posts do you know how many bottles of the anti-rust sprays (https://www.bunnings.com.au/white-knight-300g-cold-gal-silver-rust-guard-spray-paint_p0163917) will be enough? I am planning to apply the bitumen membrane to my hardwood sleepers too. Is that necessary?
You only need to coat the holes that get cut in the posts, so I imagine one can would be enough.
Applying bitumen membrane to the back side of your sleepers isn't 100% necessary, but it can help improve their longevity. As they will be treated for in ground use, they can deal with the moisture in the ground, but if you wanted to stop the moisture soaking into the back of them, it will do this and long term, that would be worthwhile.
Thank you @JacobZ. Could I have another question please? A fence guy came and suggested that I could put extra posts right next to the current posts. For some post, I will need one extra post. For a particular weak post, I will need 2 extra steel posts. What do you think about that solution? What will be the long term consequences regarding the fence and the retaining walls? Thank you for your help.
Putting in new posts near to the old ones could certainly help, but you need to ensure that the timber sleepers and fence rails are still supported. Oftentimes the butt join between separate sleepers and rails will land right on a post, so if you only added one post, only one side of rails or one side of sleepers would be reinforced and the other side, which in theory is still attached to the old rotted post, would still be weakened.
If you added a post on either side of the severely damaged posts and ensured the sleepers and fence rails are solidly attached, this should be adequate.
In theory, this would actually be stronger, so the major impact is aesthetics.
Long term, there wouldn't really be consequences outside of aesthetics as long as the posts are solidly concreted in and the sleepers and rails are solidly attached.
Thanks @JacobZ,
What the guy is planning to do is to add one extra support post near the existing post for all the fence posts, he then attaches the rail and sleepers to the extra support posts. For one particular post, he is planning to add two extra support posts. I do not want to add extra two posts for every existing posts because it is a waste of materials and aesthetics as you said. What is the solution to secure the sleepers that are on the other side of the support posts? I do not want to see one end of the sleepers to detach and move away from the retaining wall after the current posts are completely rotted. Thanks in advance.
Ultimately, the best-looking option would be to dig out the existing posts and replace them in the same spot, but your contractor is likely looking to avoid doing this.
If they're only adding one post beside some of the existing ones, then you'd want to install an additional shorter post on the other side to reinforce the sleepers.
You could use a short length of a timber sleeper as a post, like they have done in How To Build A Timber Retaining Wall. This post could be cut off at or near ground level to maintain aesthetics.
Let me know what you think.
Than you @JacobZ for suggesting that solution. It can work because the sleepers can be attached to the shorter posts. The reasons the contractor gave is that if we take out the old posts, it may brake the existing rails and palings, or the whole section of the fence may fall down. Therefore, their thinking is just to trim the tree branches, push the fence back to the line, install new posts while keeping the existing posts, then fix the rails to the new posts. They try to avoid taking the old posts out. I am not sure if that is a good solution or a messy solution that will require me do extra work later to secure the sleepers. Extra posts will create more concrete footings too. What do you think about their solution? Should I go with your initial suggestion and replace the posts?
Their solution seems fine as long as they take into account the fact the timber sleepers also need to be reinforced.
Being a fencing contractor, I imagine they've done this before, so I would trust what they are saying.
Ultimately, as long as everything is reinforced, it should be fine.
Thank you very much @JacobZ.
Hi Jacob,
Can you please give advice on the following idea?
Suppose that we are not going to take out the old post, and we want the new posts right next to the existing post instead of being at a distance from the existing post (as you can see in the picture below).
My plan is to dig out the concrete on the sides of the existing post, put the new posts in, and then pour in rapid set concrete. What will be the long term consequences of the post foundation? Will the new concrete join the remaining concrete? Or should I just dig out the existing post concrete footing completely, install two new posts, and then pour new concrete in?
What is the life expectancy of hardwood posts covered in bitumen membrane, do you know?
Also, I have this saw https://www.bunnings.com.au/ozito-18v-cordless-compact-reciprocating-saw-pcrss-018-skin-only_p0800105, will it work with hardwood posts and https://www.bunnings.com.au/australian-handyman-supplies-89-x-89mm-90-x-90-x-3-0m-galvanised-steel-fence-post_p1140455 posts? Or should I buy a new saw that can work with hardwood and steel posts?
Thanks,
Thomas
The idea of leaving the existing rotted posts and footing in place and pouring new concrete around them is not a solution that can be relied on long-term.
New concrete does not structurally bond to old concrete in any meaningful way unless it is specifically designed and detailed to do so, and even then it relies on the old concrete being sound. In this case, the concrete is wrapped around a rotted post that has already failed. Pouring rapid-set concrete beside it would simply create two separate footings sitting next to a defective one, with unknown load sharing and unpredictable long-term behaviour. There is no way to say whether it will perform properly or how long it will last.
More importantly, this fence is not just a fence. The posts are also supporting a retaining wall. Once a post has rotted at or below ground level, it is a major defect. Work-around solutions like leaving old posts and footings in place and adding new posts beside them are essentially temporary fixes. While you might stiffen the fence portion by fixing rails to new posts, you are not properly reinstating the retaining wall support, which relies on the post being in the correct position behind the sleeper joins.
Retaining wall sleepers butt into each other at their ends and are both fixed to the post behind. Leaving the old footing in place forces you into awkward solutions, such as installing posts on either side of the old concrete just to have something to fix each sleeper end to. That approach is not recommended, complicates the structure, looks messy, and often ends up being more work than removing the old footing properly.
The correct and durable solution is a full fence and retaining wall renovation: remove the fence, dig out the rotted posts and their concrete footings completely, install new posts in the correct locations so the retaining wall can be properly fixed, then reinstate the sleepers and rebuild the fence. It is a big job and there is no easy shortcut, but anything less is guesswork and risks ongoing movement, failure of the retaining wall, and more work in the future. Hardwood posts that are properly treated and coated with bitumen membrane typically last around 20 years, and in some cases even longer depending on soil conditions and moisture exposure.
Your Ozito 18V cordless reciprocating saw will likely struggle cutting through hardwood posts, especially thicker sections. For cutting hardwood, a 240V circular saw is much more efficient and will give cleaner, faster cuts.
You should not attempt to cut the galvanised steel posts. It’s far better to select posts of the correct length from the start. The only tools that can realistically cut those steel posts are an angle grinder.
Please let me know if you have any questions.
Mitchell
Thank you @MitchellMc,
I agree with your solution and I think it is best for the long term.
Regards,
Thank you @MitchellMc and @JacobZ for your supports so far.
Here is my plan to fix my fence posts.
Step 1: Install two https://www.bunnings.com.au/jack-240cm-black-premium-ultrapost_p3041483 on either side of the old posts. The jack will be installed outside of fence on lower ground to provide supports.
I have already used some rails to support and straighten the fence in place in addition to the Jacks.
Step 2: Attach fence rails to the Jacks.
Step 3: I will dig out the old concrete using https://www.bunnings.com.au/full-boar-1050w-7kg-sds-max-demolition-hammer-kit_p0094370
While digging out the concrete, I apply two coast of https://www.bunnings.com.au/gripset-betta-1l-waterproofing-membrane-bitumen-rubber_p0960165 to the part that will be underground of the new post and let the membrane set.
Step 4: Take out the top rails and a few palings that are close to the old post so that I can unscrew the middle rails out of the old post.
Step 5: Take out the old post.
Step 6: Put the new post in.
Step 7: Attach the horizontal (middle) rails back to the new post
Step 8: Make sure the fence straight.
Step 9: Pour the concrete in and let it set.
My question are:
Thanks in advance
Thank you, @JacobZ.
I will post you my progress as I work through the project.
Also, do you know when I need to use this tool?
https://www.bunnings.com.au/ozito-pxc-18v-brushless-planting-and-digging-tool-skin-only_p0404529
Is this tool more appropriate to build a new fence or plant a tree rather than fixing and digging out old concrete?
If you're digging out the old concrete, then there will already be a hole, so you don't really need it.
If you were digging new holes, it would be handy but also is likely underpowered for the depth and diameter of hole you need. If you needed to dig new holes, you would be better off hiring a Post Hole Digger with a 300mm diameter auger bit.
Hi @JacobZ and @MitchellMc,
Can I have few additional questions please?
The old fence guy used 200x50 mm sleepers https://www.bunnings.com.au/200-x-50mm-2-4m-treated-pine-sleeper_p8032702. Should I use 200x75mm sleepers https://www.bunnings.com.au/200-x-75mm-2-4m-treated-pine-sleeper_p8032710? for extra thickness, but wrong size. Or should I just keep using the 200x50mm sleepers, so they are not out of order with the existing sleepers?
2. I have chosen hardwood posts.
Do you know which screws should I use with the hardwood posts so that the screws do not create cracks and r when drilling in the hardwood posts? Please recommend screws that can be used with https://www.bunnings.com.au/ozito-pxc-18v-cordless-compact-drill-and-impact-driver-kit-pxcdik-250_p0195859. . If none is available, please recommend a tool that I can use with the screws.
Thanks in advance.
For the sleepers, it’s best to stick with the same size that’s already there, in your case 200 x 50mm. If you switch to 200 x 75mm, the extra thickness will push that section forward and it won’t sit flush with the existing sleepers. Structurally it’s not necessarily a problem, but visually and alignment-wise it can look out of order and make fixing everything up more difficult. Matching what’s already installed will give you the cleanest and easiest result.
Regarding the hardwood posts, they’re much stronger and more durable. Hardwood is dense, though, and it’s very important to pre-drill your holes. If you try to drive screws straight into hardwood without pre-drilling, there’s a high chance of splitting the timber or snapping screws.
A suitable option would be something like Buildex 14G x 125mm Class 4 Bugle Batten Screws. They’re heavy-duty, corrosion-resistant (important for outdoor use), and strong enough for sleepers into posts.
Before installing them, pre-drill through both the sleeper and into the hardwood post using a quality drill bit such as Kango 4mm Long Series HSS Drill Bit. Pre-drilling reduces pressure on the timber and helps prevent cracking. You may even consider going slightly larger (for example 5mm) depending on how hard the timber is — the pilot hole should be slightly smaller than the screw’s core diameter.
Your Ozito PXC 18V Cordless Compact Drill and Impact Driver Kit PXCDIK-250 should be fine for this job. Use the drill to pre-drill the holes first, then switch to the impact driver to drive the screws in.
Thanks @MitchellMc,
Do you know if this drill bit https://www.bunnings.com.au/sutton-tools-5-0mm-long-series-jobber-drill-bit_p6353673? will suit the job? I ask because the Kango series are not available at my local store.
It should be fine, @ThomasBNE. However, I went with the 4mm to be sure that the screw threads grip the timber. You really want the drill bit to the the same thickness as the inner screw section, which I've marked below. Do they have the Sutton Tools 4.0mm Long Series Jobber Drill Bit? Alternatively, you can use a standard length 4mm drill bit, I just chose the long series as they let you drill to a greater depth.
Thanks @MitchellMc, they have https://www.bunnings.com.au/sutton-tools-4-0mm-long-series-jobber-drill-bit_p6351998 and I will use it to pre-drill.
Hi @MitchellMc and @JacobZ ,
I would like to hear your advice on digging out the concrete stump.
I use the demolition hammer
https://www.bunnings.com.au/full-boar-1050w-7kg-sds-max-demolition-hammer-kit_p0094370
and it cuts through top concretes quite fast. However, my progress cutting concrete at the bottom is quite slow. The situation is a little bit complex because one side of the fence is higher than the other of the fence. From the higher side of the land, I have already dug about 80cm. From the lower side of the land, I dug about 40 cm. When getting deep, the tool movement is limited. I am cannot cut through the concrete as fast as when the concrete on the top.
What should I do to make digging out the old post stump faster? Do I need hire or buy another tool or just make the hole bigger so that I can move the tool easier?
I would be trying a wide bladed crowbar, manual post-digger and a small trenching shovel.
Hello @ThomasBNE
@Noyade has made some excellent suggestions especially the use of the long-handled crowbar. If you have this type of tool at your disposal it would be the right tool to get to the bottom end of the concrete footing. You also have the choice of getting a For Hire: Coates Large Breaker - 5+ Days or invest in a Mumme 1800mm Pit Bar. The pit bar is a manual tool that is used to slam down onto the concrete surface to break it apart.
If you need further assistance, please let us know.
Eric
Thank you @Noyde and @EricL,
I purchased https://www.bunnings.com.au/cyclone-1800-x-25mm-hex-crow-bar_p3360665. This tool make digging dirt easier. For concrete breaking, I still relied on the demolition hammer. Finally, I got the stump out.
I purchased this chisel https://www.bunnings.com.au/diablo-250mm-sds-plus-pointed-chisel_p0356766 to use with https://www.bunnings.com.au/full-boar-1050w-7kg-sds-max-demolition-hammer-kit_p0094370.. The chisel is really good. However, it is quite short.
I am just wondering if there is any chisel that is longer than 250mm and can be used with the demolition hammer (https://www.bunnings.com.au/diablo-250mm-sds-plus-pointed-chisel_p0356766)?
I'm glad to hear you got the stump out. In regard to the 250mm chisel head, there are longer chisels such as the Craftright 350mm SDS Max Pointed Chisel, the Craftright 350 x 40mm SDS Max Flat Chisel and the Craftright 350 x 25mm SDS Max Flat Chisel Bit. But these are rated for light demolition tasks only.
Let me call on our experienced members @Nailbag, @Dave-1 and @Noyade for their recommendations.
Hi @ThomasBNE
You're not going to get any further down at this point with DIY powertool. And you can't get long enough accessories for an SDS+ fitment tool. It need a more commercial SDS Max and above. It's now all down to yourself making the hole bigger than you want unfortunately using the hand tools that @Noyade has recommended to dig around the concrete until you get to the bottom and can pull it out. It's a tough back-breaking long job. I use to use the exact same set of hand tools, but I now avoid these jobs as my ageing body complains to much afterwards. When it come with dealing with a larger hole, instead of filling it with multiple bags of cement, use broken up sections of the old concrete and a few other masonry items like half bricks, broken roof tiles, and rocks. All of this combined with the cement will provide for an even stronger foundation. But it's very important that you are layering the concrete down in-between the rubble. Poor rapid set down the gaps, add the water and then use your crowbar to stab-mix it in and repeat. Nailbag
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