How to treat cracked Merbau decking?

https://www.workshop.bunnings.com.au/discussion/comment/45143#Comment_45143

Hi @wooshka,

Thanks very much for your reply. Yes, we are a bit disappointed. From far the deck looks nice, but it's a bit of a mess up close, and the cracks may show more as it ages. The deck has been hosed off a few times already and lost quite a lot of tannin, so it doesn't seem like it was left out in the weather before being delivered. It was installed a few days after delivery.

We'll ask for some of the decking to be replaced, but not sure if we should ask them to replace all of the cracked lengths, as there are about 100 cracks in maybe 60 lengths. We're also concerned about drilling into the joists too many times, although they're 140x45 treated pine, so should be ok, just keen to reduce the chance of rot in the future as we live in a very wet part of Vic.

David

https://www.workshop.bunnings.com.au/discussion/comment/45148#Comment_45148

Hi @Nailbag,

Thanks very much for your advice. The installer has advised that they were drilling pilot holes on the ends, but not in the middle of the boards, with a drill bit the same size as the screws. A regular drill bit, not a countersinking one. The screws are also designed to not require a pilot hole.

Simpson Strong-Tie 12G (5.5mm) x 65mm 316 Stainless Steel DHSD No-PreDrill Hardwood To Softwood Decking Screws

There are about 100 cracks in 60 boards on a 60m2 deck, which is a lot for the installer to supply and replace. Also, do we risk the integrity of the joists long term if we screw into them too many times and leave empty holes for water to sit? They're 140x45 treated pine, but we live in a very wet part of Victoria.

David

https://www.workshop.bunnings.com.au/discussion/comment/45144#Comment_45144

Hi @EricL,

Thanks very much for your suggestions. Replacing all of the cracked boards seems like the best option, although that's about 60 boards on our 60m2 deck. We're also concerned about creating too many empty screw holes in the joists for water to sit and potentially cause issues in the future, although they are 145x45 treated pine. Do you think the joists would be ok?

David

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/84668#Comment_84668

Hi @David10,

I'm really sorry to hear about the issues with your new decking.

Replacing the affected boards is likely the best solution to ensure the deck looks and performs as intended. Thankfully, removing and re-screwing boards shouldn’t compromise the integrity of your joists, especially given their size and treatment.

It might be worth speaking with a manager at the store of purchase. I trust they'll do their best to help resolve this situation.

Mitchell

twocutekelpies

I wonder if the screws are too close to the edge? We've just done our deck and while we pre-drilled (hardwood joists) and pre-countersunk, we also kept them in a bit from the edge. (Edit, sorry, I missed that you did mention this)

I also wonder if it's worth flipping a board, pre-drilling, countersink and then re-screwing using the existing hole, if that would work. Save replacing so many boards if it comes to that. Hopefully installer will replace though.
Do you know if they laid joist protection down before laying deck? If the deck needs to be re-done, fresh joist protection would cover existing holes.

Nailbag

https://www.workshop.bunnings.com.au/discussion/comment/84668#Comment_84668

Morning @David10

The benefit of pilot holes as you may know is to both stop wood from splitting and provide a much more secure bond of the top material. As the bit is drilling each hole, wood is being removed which provides the relief of pressure from the fastening screw. When using those types of 2-in one deck screws the wood isn't being removed, so there will be outward pressure. This means it's even more critically important to place the screws 20mm - 25mm with 140mm boards and 17mm - 20mm with 90mm ones. Your photos show that the screws are all very close to the edge making the boards easier to split. The other reason for additional pressure, is those screws are not providing a countersink for the head. So, more pressure is applied as the screw is driven home and leaves those very rough edges around the head.

Here is an example of way to close to the edge

Screenshot 2024-11-27 at 7.21.12 am.png Screenshot 2024-11-27 at 7.22.02 am.png

I would recommend as @EricL has to repair the boards buy removing and repairing one board at a time. I would recommend using this high-strength wood glue by Gorilla and then clamp until the recommended curing time has expired. I would drill out each hole before re-laying. The same length screw should be fine if the joists are new. Otherwise you can get longer ones for greater peace of mind. Alternatively you can use pre-drilled and countersunk batten screws which I use.

Nailbag

The same

https://www.workshop.bunnings.com.au/discussion/comment/107390#Comment_107390

Good Morning @David10

Thats a pain to deal with 😕

Going forward I would be replacing the boards ( I do have the same thoughts as @Nailbag as to remove, using a glue and clamping together to repair the splits but not confidant it will work well)

The concern over screing more screws into your supports -

- Id probarly be concerned as well even tho I know it really shouldnt make a huge amount of differance. You could always paint waterproofing material over the supports with the boards being replaced.

Reusing the boards -

Even tho I have hesitation on repair of the boards id still give it a go. There is nothing to loose if it works. In theory you could put the same piece back in (therefore reusing the existing holes) and then redrill the holes near the splits that you have repaired. (with a countersunk pilot hole)

Dave

Nailbag

Hi @David10

I showed these photos to a registered builder mate of mine and he confirmed the main issue is that the screws have been installed to close to the edge, which puts the issue back on the installer to make good.

If it's going to be an issue, a compromise could be to lift the damage boards, and cut the affected area and refit. Then fill the gaps with infill boards as long as they aren't too short for aesthetics. There are also unacceptable gaps between some boards which isn't acceptable in a professional built deck as per the photo below. Again back on the installer.

I know this puts you in an uncomfortable position between yourself and the installer, but you have paid what I would imagine a large sum for this deck and there shouldn't be any issues like these.

Screenshot 2024-11-27 at 10.33.01 pm.png

Nailbag

Hi everyone,

Thanks very much for your help on my last post. Our carpenter has fixed up a few of the worst areas, but we still have some concerns. The deck is looking nice at first glance, as you can see from the first photo, just some of the finer details are a bit rough/potentially need some more work.

1. Our carpenter used the below decking screws which are not supposed to require a pilot hole, however they've left about 100 cracks in the boards. The consensus has been that many of the screws are too close to the edge of the boards and he should have switched to drilling countersunk pilot holes when they started cracking. He's now doing this when replacing boards.

Simpson Strong-Tie 12G (5.5mm) x 65mm 316 Stainless Steel DHSD No-PreDrill Hardwood To Softwood Decking Screws

Our decision now is what to do with the cracks. We could ask the installer to supply and replace all the cracked boards, but that's about 20m2 of decking and most of the cracks are very fine. Is this an issue long term? We've been advised that the cracks will become more noticeable over time, especially after oiling as the oil will sit in the cracks. Or we can just leave the cracks and live with it. Will they rot faster, as water sits in the cracks?

The wedges in the first photo are marking cracks on half the deck.

2. We feel the end decking board at this step could be finished better, but we're not sure. At the moment it's bent down on both sides to slide under the existing stair stringers, however can't some of the stair stringers be shaved off to give the decking board more room? If so, what tool would be best to use? It would need to fit in that gap and leave a neat finish.

There's also a join on the left side, when it looks like one board could have been used. Use a longer board, slide it under one side, lay it down and then bring it under the other. is this straightforward to do?

462566918_1304478347532825_5094795876282288124_n (1).jpg

3. Quite a few very rough screw holes. These occurred when using the countersinking drill bit with the depth stop removed. The installer removed the depth stop in some areas under the existing hand rail where he couldn't use it, but didn't put it back on when he moved back to unrestricted areas where it could be used. Most of these rough screw holes are not in obvious areas like under the handrail.

P&N Quickbit Smart Countersink Drill Bit

Do we just need to take to these with a bit of sandpaper, or are they more difficult to tidy up?

4. When our installer switched to using the countersinking drill bit with the depth stop removed, some of the holes were quite deep. Our concern is water will sit in these holes and reduce the deck's lifespan. Should these boards be replaced? We live in a very wet area of Victoria.

5. Can this rough edge be fixed up with sandpaper?

6. What tool could we use to take off some of the bottom of this existing post to bring the decking board up level with the rest? Is that appropriate to do?

7. Should we replace this board or will this mark fade over time? It doesn't bother us too much, just more wanting to know what's usually done.

Any advice would be greatly appreciated.

David

https://www.workshop.bunnings.com.au/discussion/comment/45640#Comment_45640

Afternoon @David10

Thats a few questions 🙂 lets see if Ican go through them.

Q - Our decision now is what to do with the cracks. We could ask the installer to supply and replace all the cracked boards, but that's about 20m2 of decking and most of the cracks are very fine. Is this an issue long term? We've been advised that the cracks will become more noticeable over time, especially after oiling as the oil will sit in the cracks. Or we can just leave the cracks and live with it. Will they rot faster, as water sits in the cracks?

A - Your installer should be replacing the cracked boards at their cost. Especially once they cracked while installing and then continuing the install. All that goes through my head is a bair foot dragging across the floorboards and swick....... followed by a scream 😕 floorboards need to be free of slivers.

1- We feel the end decking board at this step could be finished better, but we're not sure. At the moment it's bent down on both sides to slide under the existing stair stringers, however can't some of the stair stringers be shaved off to give the decking board more room? If so, what tool would be best to use? It would need to fit in that gap and leave a neat finish.

1a - The more I look at your photos the more I think the weight of the steps are resting on that floorboard and not really supported. The boq in the timber really heads my mind towards this. I would suggest to investigate how the steps are attache dto the edge of the deck, working backwards from there you should be able to see what is missing and how those two "arms" should be resting.

2 - There's also a join on the left side, when it looks like one board could have been used. Use a longer board, slide it under one side, lay it down and then bring it under the other. is this straightforward to do?

2a - I would say its not a simple thing to do as all the weight seems to be resting on the top board and not the side. The steps should have been supported / lifted even when the board was installed. They seem to have taken a short cut?

3 - Quite a few very rough screw holes. These occurred when using the countersinking drill bit with the depth stop removed. The installer removed the depth stop in some areas under the existing hand rail where he couldn't use it, but didn't put it back on when he moved back to unrestricted areas where it could be used. Most of these rough screw holes are not in obvious areas like under the handrail.

P&N Quickbit Smart Countersink Drill Bit

Do we just need to take to these with a bit of sandpaper, or are they more difficult to tidy up?

3a - These are an easy fix, You could use a large drill bit and dusing your hand just twist the drill over the hole, it will champher off any of the left over strands of timber. You could also use a wide chisel gently, just rid ethe chisel over the area with the flat part of the blade facing down. Dont push too hard a syou dont want to add scratches to the boards.

4a - This one is a personal preference Ithink. I have done some too deep countersunk holes on my deck and have had no issues in ten years. The deck is open and also next to the pool. I have also just done a timber top to a gabion wall and steps that are very much like the picture. I figure they will drain ok and used more oiling when I oiled. You could also put timber plugs in them if concerned. Using a hole saw cut out the same dimension as your existing holes, then insert them into the hole using glue. once dry use a chisel to tap off the excess.

5. Can this rough edge be fixed up with sandpaper?

5a - Yes it can be but id suggest to use a file to smooth first as its quiet rough. Sandpaper will just take longer.

6. What tool could we use to take off some of the bottom of this existing post to bring the decking board up level with the rest? Is that appropriate to do?

6a - I would be reluctant to do chop off any of the existing post, A multi tool is what i would use if you went that way. The installers should have smoothed the dip out when installing the boards. One of the supports probtally has dropped some.

NOTE - the previous photo for this question looks like it has rotted timber. have you accessed the underlying timbers and posts for any rot?

7. Should we replace this board or will this mark fade over time? It doesn't bother us too much, just more wanting to know what's usually done.

7a - I wouldnt replace the board, the spot may fade with time. You could scrub with a course brush and soapy water or even sand it a little if it is still there afterwards. Decking has its own indervidual marks, just depends on how much it catches your eyes.

For all the imperfections that you have raised my first step woyuld be to get the installer back and go through them all (as a list) and decide upon what can be done and what can be lived with. They have installed it and it needs to be safe (the splits in the timber) The licence they have and fair trading would be something I would get as well.

Dave

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/45640#Comment_45640

Hi @David10,

@Dave-1 has provided some great answers there and my thoughts mirrors them. I just wanted to let you know that we've sent your images off to the Simpson Stong-tie technical team to take a look at and will update you on their response.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/84927#Comment_84927

Hi @Dave-1,

Thanks very much for your detailed reply.

As you can see in the photos, some of the cracks are very small. If our installer refused to replace them, are even these small cracks likely to cause issues? We may have to decide whether to pay someone else to supply and replace these boards or live with them.

1. The steps were left in place and used while the deck was being redone and I don't think the deck is providing much if any support. See photos. I think most of the force is going into the side of the old cladding (not sure if that's the right term) and into a stump behind.

2. I believe the existing handrail is nailed to the existing posts, so dismantling it may have been difficult when redoing the deck. Our installer said he didn't want to cut the stair stringer as it wouldn't have been a clean finish, so bending the board down to fit under was his solution. But it seems like with the right tool, the stringer can be cut where it meets the new deck, to allow the deck to be level and not bent down. I'm just not sure what the appropriate tool is. Reciprocating saw? Multitool?

4. Good to know. The deep holes do seem to eventually drain.

6. We assessed for rot before redoing the deck. The existing decking and joists were the worst, but the handrail and posts weren't too bad. Some superficial rot. We'll replace the handrail and posts later if needed.

We'll be getting the installers back soon to go through everything, I just needed to get my head around a few things first. As i mentioned, some of the splits in the timber are very small, and we're not sure how much to ask them to replace. Obviously if they're large, visible and possibly dangerous they'll be replaced, but some are very small, maybe less than 0.5mm width and 20mm long. Should these all be replaced? During an earlier conversation with our installer when I first noticed the cracks he mentioned that cracks on the end of the boards is common, but not in the middle, and also crack defects only need to be addressed if they're visible from more than 1.5m or so. Is this valid or is he just trying to avoid responsibility?

For reference the boards are 90mm wide. I tried to take a variety of crack photos in my post yesterday, showing large and small ones.

David

https://www.workshop.bunnings.com.au/discussion/comment/84928#Comment_84928

Hi @MitchellMc,

Thanks very much for that. Keen to see what they think.

David

https://www.workshop.bunnings.com.au/discussion/comment/107583#Comment_107583

Good Evening @David10

With the splits in the timber it really is going to come down to how you feel about the decking. You could have 10 differant opinions on what to do but its your deck so better to go with some kind of cut off point (say certain splits are a no while others are so so)

The tool you are after is a multitool, they look very handy and ive only used one once but its on my list 🙂

The steps and how they are resting, another one that is up to you, leave as is for the time being and then plan to do something if it becomes a problem?

Its good that you assesed the timbers, makes it a non stress process down the track.

As to cracks being common, id say nope. Ive never heard of that before and no one has mentioned it in the posts I have seen in here unless there was a problem. You could ask for photos of examples elsewhere but it would be better to balance between getting it fixed at their cost and a going down the route of a complaint. Hard call but something that could save you more hassel.

Dave

https://www.workshop.bunnings.com.au/discussion/comment/107584#Comment_107584

Hi @David10,

We are still waiting on a response from Simpson, please bear with us, we will update you as soon as we hear back from them.

Jacob

https://www.workshop.bunnings.com.au/discussion/comment/107584#Comment_107584

@David10,

We've received a response from Simpson. They have reviewed the discussion and agree the screws were positioned too close to the edge of the board.

These screws come collated (on a strip) and were designed for use with their Quik Drive Auto-Feed Screw Driving Systems which uses the PDECKNC-RC nose clip to set the screws at a consistent 20mm in from the edge of the board. When the screws are closer to the edge, without pre-drilling you run the risk of splitting the timber.

Please let me know if you need further assistance.

Jacob

https://www.workshop.bunnings.com.au/discussion/comment/121086#Comment_121086

Hi @JacobZ,

Thanks very much for contacting Simpson.

The majority of the cracks are at screws that are closer than 20mm from the edge, however quite a few are at 20mm. I've attached a few more photos.

Could the timber being very dry cause this? It was installed a few days after delivery.

David

https://www.workshop.bunnings.com.au/discussion/comment/129450#Comment_129450

Hi @David10,

Yes, dry timber will lose some of its flexibility and is likely a contributing factor to the cracking.

Ultimately, a combination of things will have caused the cracks and if the installer were to do it again, they should predrill all the boards to ensure it doesn't happen again.

Let me know if you have any further questions.

Jacob

https://www.workshop.bunnings.com.au/discussion/comment/134749#Comment_134749

Hi @JacobZ,

It looks like pre-drilling with a countersink has taken care of most of the cracking, but our carpenter has had a look and was frustrated as at least one board has cracked, even with pre-drilling. So it seems like some cracking may be unavoidable? Or maybe too high setting on his impact driver could contribute? The board seems like it might crack easily as there's a crack in the second photo that's not even at the screw.

Are cracks like these normal or acceptable in a new merbau deck? Mostly keen to understand what's normal and what we should be telling our carpenter.

David

https://www.workshop.bunnings.com.au/discussion/comment/138193#Comment_138193

Afternoon @David10

In all the times I have used merbau decking it has split on my twice, and thats because I was going to close to the edge on purpose (was making a bracket edge) and overtightened after the predrill.

Courtyard privacy fence and gate build, Part 2 Step 4 fourth photo up on the handrail is the split I caused. It was because I was predrilling the 19mm width to go into the flat handrail and I didnt have my drill absolutly vertical 😕

Were they new boards that cracked? If so then possibly the torque/impact driver was too high. I have used Merbau that has sat in the garage for 6 months waiting to be used and there was no issue. I use a torqued driver not an impact drill. Impact drill, I have issues with screws shearing off when I go into hardwood posts through hardwood decking.

Dave