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Yet another deck in need of help

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  1. #1
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    Default Yet another deck in need of help

    Hi people,
    Iíve started to fix up a deck that has newish merbau boards but posts and railings are much older and in poor shape, with splits, cracks and rotting soft areas.
    After spending a few nights reading all the deck related posts on this forum (such a great source of info and advice) I think I know what I need to do for the merbau but not the posts and rails.
    I know that the long term solution is replace them, but I canít afford that yet, so I need to get another 5-10 years out of them.
    What options are there?
    Fill the cracks with epoxy? CEPS? Paint it with oil every few months? Try all these things?
    Thank for any ideas,
    neale

  2. #2
    Seasoned DIY droog's Avatar
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    Pics would be a good starting point.

    And welcome.

  3. #3
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    Attachment 129808Attachment 129809

    thanks droog, although I’ve had a login for 10 years, I’ve never posted before. The YouTube vid on how to attach pics was very handy.
    these posts and top rails are 150mm square, not sure what kind of timber.

  4. #4
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    Can't see your photos,but if the posts and handrails need numerous repairs,painting them,then staining the deck surface may be the best plan.
    Cheers,
    Blocker.

  5. #5
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    Quote Originally Posted by nealeb View Post
    Attachment 129808Attachment 129809

    thanks droog, although Iíve had a login for 10 years, Iíve never posted before. The YouTube vid on how to attach pics was very handy.
    these posts and top rails are 150mm square, not sure what kind of timber.
    Try to send photos again.

  6. #6
    Community Moderator phild01's Avatar
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    Hi Neale, pics won't upload if file size is large, you may need to reduce the pic size, mspaint is good for that.

  7. #7
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    thanks, I'll get the old computer out and get some photos working.

  8. #8
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    handrail1.jpghandrail2.jpghandrail3.jpg
    Hope these pics work...
    I pressure washed everything to remove grime and then let it dry before hitting a few areas with a sander to see how the surface felt... pretty soft...
    since i was thinking of the cutek oil for the deck, how about using cutek preservative for the handrails? or should the deep and open cracks get filled with something first? then sanded back and then oil everything?

  9. #9
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    So I spent about 5 days sanding posts and handrails... then another 2 days replacing 9m of handrail with some 145x145 that a mate milled up for me. Came up pretty nice, by my fairly low standards anyway Now I'm looking for some advice on the next phase...
    finished-rail.jpg

    Next job is to fix up rotten bases of posts. Some are pretty bad, some are really bad and one or two are OK. They are 150x150 hardwood in the ground, with concrete around them. They have been partially covered with soil for years and need work to keep them sound. I dug around a few of them and the concrete is at least 350mm deep (gave up digging) and averages about 400-450mm diameter.
    post1.jpgpost2.jpgpost3.jpg

    My idea is make a custom steel stirrup that I can bolt to the existing concrete and fix into the solid timber about 200mm up the post. I have access to an amazing steel working workshop so fabrication is relatively easy. I will use 125 PFC sitting vertically on an 8mm base plate and get it HDG. Fix into concrete with 4xM12 chemical studs and into post with 2xM10 bolts or coach screws. This looks more solid than the Pryda stuff (that doesn't suit my size posts or easily solve the problem at hand)... and i think my design will be plenty strong enough by comparison. Sketch below.
    new-base.jpg

    My question is mainly - should I cut the post above the rotten sections (currently up to 100mm above concrete level) and have the post bear onto my new stirrup? Or should I just leave the rotted part untouched, and fix in the new stirrup acting as a brace or support?

    I suppose cutting it means lower termite risk, and less progression of rot in the future. But the deck is standing and not floating or moving, so why cut?

    It ranges about 1m to 2.2m off the ground and has 20 posts. I will also fit some bracing as part of this work.

    The only other solution I can think of is a hell of lot more work: Dig out the concrete, break it up, cut the post, fit a Dunnings stirrup and pour a new footing with the stirrup cast in. With 20 posts, that is a massive job for me.

    Any advice or ideas would be appreciated. thanks
    Attached Thumbnails Attached Thumbnails post1.jpg  

  10. #10
    Seasoned DIY droog's Avatar
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    First thing is how high off the ground is this deck?
    If its low set then your idea might work, but rotten timber is like a sponge and retains water so get rid of any rot.

    If its a high set deck I would be re-doing the post and footings from scratch probably all in steel, and better to get an engineer to look over your plans.

  11. #11
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    Quote Originally Posted by nealeb View Post
    My idea is make a custom steel stirrup that I can bolt to the existing concrete and fix into the solid timber about 200mm up the post. I have access to an amazing steel working workshop so fabrication is relatively easy. I will use 125 PFC sitting vertically on an 8mm base plate and get it HDG. Fix into concrete with 4xM12 chemical studs and into post with 2xM10 bolts or coach screws.
    Be interesting on what others think.
    Some assumptions: If they were all centered in the hole, and the hole was 400mm square, then you would have 125mm of good concrete each side or 150mm if they were 450 wide footings..
    You would also assume post go down to the bottom and that they are simply non existent inside the concrete footing from a structural view point.
    or if the footings were squared off vertically

    So at best 125 to 150mm strip of concrete each side of the post but is it going to provide enough structural integrity with a deck 1m to 2m off the ground?

  12. #12
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    Deck is between 1m and 2.1m off the ground.

    Posts look to be in good condition other than what was in the ground. The bearers, joists and deck are all new. The only crappy bit is that crucial bit that connects it to the earth!

    So you reckon cutting is preferred? and seek an engineer

  13. #13
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    Yeah, a post sunk deep in a hole, with concrete around it will be strong for bending loads compared to my idea of stirrup bolted to a donut-shaped ring of concrete. But, if braced, those bending loads will be small. And if this was a new deck build, and off-the-shelf stirrups were used, wouldn't that be the same situation?

    I had a deck built 8 years ago at my old house with Duragal flooring system, 3.5m from ground. Post bases were simply 2xM12 tru-bolts into top of concrete.

    These Pryda ones could be useful for me but I would have to cut the post, remove what I can from the rotten wood inside the footing, then fit the Pryda and cast it inside the hole left by the old post.

    https://pryda.com.au/product/adjustable-post-anchors/

  14. #14
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    A high set deck presents a greater injury risk in the event of collapse, in good condition when built the posts would have provided significant bracing of the entire structure which is no longer there.
    Your ideas would most likely provide sufficient vertical support but bracing for the structure needs to be confirmed and or addressed.

    https://ibcnsw.com.au/deadly-decks-a...onies-warning/

    For that height I would speak to an engineer and have an onsite assessment done.

  15. #15
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    thanks Droog - I know an engineer from previous jobs - I'll get them out to take a look. The consequences and long-term serviceability are not worth bodging it up.

  16. #16
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    Make your own stirrup, with PFC or angle, but forget bolting to a footing that has such large hole in it.
    Consider acro prop, and jackhammer the footing, bolt new stirrup and pour new concrete.
    Peace of mind.
    Check high wind stirrup you can buy off the shelf, they may work out too, always in fresh concrete though
    https://pryda.com.au/product/high-wind-post-anchors/

    If you make your own, HDG is usually costly due to minimum charges around 100 kg

  17. #17
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    So if I do prop, cut bottom of posts off, remove whatever is left of the post from in the concrete footing, however deep that might by, why not just cast in a new stirrup in that 150 square hole? That’s how heavy machines are held down in factories and plant rooms the world over. I know they use tapered holes so they are keyed in, but a deck with no roof doesn’t haven’t much lift.
    I like to present ideas to the engineer so he can say no…
    and I’m sure it’d be almost impossible to remove all the old post from inside the footing…

    there are also these guys. https://surefootfootings.com.au/ I’ve used them and like them, but you need free space overhead.

    thanks for the advice Marc, droog and Bart. doing things the standard way is always best but sometimes quicker, easier alternatives can achieve almost the same outcome. I’ll go find myself a jack hammer and cement mixer.

  18. #18
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    Dug out 3 footings today. Wasn't much post left in the ground on one of them... just compost. Jack-hammered out all the concrete and found that posts were dug down to rock, about 600-700mm down, and back filled with weak concrete. So I'm glad for the advice received here not to bolt into it.

    hole1.jpghole2.jpg

    Casting in Dunnings Tornado stirrups, with each hole taking 12-15 bags.

    Also fitting M12 g8.8 threaded bar as cross bracing, similar fashion to Duragal flooring system specification.

    3 down, 21 to go, woohoo. Going to cost over $5,000 but will last a good deal longer than what I have right now.

  19. #19
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    Quote Originally Posted by nealeb View Post
    Casting in Dunnings Tornado stirrups, with each hole taking 12-15 bags.

    Also fitting M12 g8.8 threaded bar as cross bracing, similar fashion to Duragal flooring system specification.

    3 down, 21 to go, woohoo. Going to cost over $5,000 but will last a good deal longer than what I have right now.
    Dont buy in bags, it will cost you way less.

    Either dig the holes and get a mini-mix or buy sand screenings mix and add cement if you want to mix your own.

  20. #20
    Deactivated User Marc's Avatar
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    Mix your own.
    Use concreting sand and aggregate mix, 4 of the mix for one cement in volume.
    You can even mix in a wheelbarrow, using a mattock. A bit slow but works.

    15 bags of concrete mix per hole seems a bit high. What size are the holes?

  21. #21
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    Holes ended up 500 dia by 700 deep. Online calculators said about 15 bags I think.

    Do I just buy sand and aggregate mix from the landscape supplier? and then bags of cement? who is best to buy from?

    A mate is lending me his mixer which will help

  22. #22
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    Yes, landscape supplier concreting mix.

    Just in case someone tells you different ... if you want to make a strong concrete mix you go 3/2/1 that is in volume 3 stone, 2 sand and one cement.
    If you mix 3 bucket of stone with 2 buckets of sand, you don't have 5 buckets of mix. The sand will go between the stones and the volumes will contract to approximately 4 mix in volume.
    Furthermore the landscape supplier mixes the sand and aggregate using a bobcat or tractor front loader, so it is far from accurate. They mix it 50/50 in the best of cases.
    So if you go 4-1 mix and cement, you will have a slightly higher amount of sand than 3-2-1, but perfectly adequate for strong footings.
    Some suppliers have a choice of stone size in the mix. Go for the 20mm stone if you have the choice. Otherwise don't worry. 10mm is OK

    Who to buy from in the Blue Mountains, I don't know, but any local supplier should be fine providing the price is OK.
    Sand and gravel mix is around $85 a ton plus delivery and grey cement $9 a bag.

  23. #23
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    Thanks Marc, that is good to know. I've never had to make more than a few bags worth of concrete before, and it didn't occur to mix my own, so thanks for pointing out the savings to be made. Also good to know about the stronger mix ratio if I need to do something else in the future.
    I have Tunks Landscapes in Katoomba - I'll get a ton of sand-gravel mix from them and see how far it goes.

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