Water pooling on deck

Forums › Home Workshop DIY › Water pooling on deck - solutions?

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#3118753 21-Aug-2023 19:00

concordnz: Hardwood decking can be fitted a lot closer as it doesn't expand in the wet, like Pine does.

Although shouldn't it still have some gap? Are there recommended gaps for both pine and hardwood?

Bung

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#3118755 21-Aug-2023 19:11

I've run a circular saw along the gaps on pine and kwila desks. You do need to be careful not to get the blade jammed or the kickback could leave a gouge. I did round the edges off, it doesn't take long for the new edges to age. Narrow kerf blades are common on battery saws to reduce the load. I used a 165mm narrow blade on a 185mm corded saw.

The waterlogged deck looks like it has gaps outside the wet area that would help get started then don't push to hard.

I don't worry about slightly wider gaps. It’s easier to clear the rubbish out and it won't be my phone that falls through.

Edit: any timber decking that hasn't been sealed will expand if it gets wet.

mdf

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#3118756 21-Aug-2023 19:16

mattwnz:

concordnz: Hardwood decking can be fitted a lot closer as it doesn't expand in the wet, like Pine does.

Although shouldn't it still have some gap? Are there recommended gaps for both pine and hardwood?

Wood expands when wet and shrinks when dry. (Almost?) All wood will come from the sawmill with a much higher moisture content than it will have once it has "acclimatised" to its location (even outdoors). So after a few weeks, fences, decks etc. will usually have bigger gaps than when they are first installed. So you can get away with installing timber "tight" and rely on it to shrink a little bit.

I suspect here because the water is sitting in constant puddles, it has expanded back to installation size. Usually you expect even outdoor wood not to be fully submerged. But painting it might help with this since it will seal the timber and stop it sucking up quite so much moisture.

jonathan18

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#3118762 21-Aug-2023 19:43

Wombat1: Timber will need to be lifted. Anything else will be a half job.

However, as my OP clearly states, I am looking for options other than lifting the boards; your half-arse job is my acceptable solution, no doubt, and in the end I’m the one living with the decision…

I have a feeling the clean out / water blasting I’ve done today will see us through the next few weeks until the builder’s here to work on the fence. I can then also pick his brains for the best solution to my exact problem, but I imagine trimming with a circular saw will be feasible. There is indeed a decent gap between the boards further back (under a veranda), so shouldn’t be too big an issue to get the blade in.

Thanks for the ideas and feedback; I’m glad I checked in before drilling lots of holes across the deck!

jonathan18

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#3118763 21-Aug-2023 19:46

jonathan18: Anyway, while on the question of decks - what would people recommend as the most effective deck cleaner? I don't want to stain it, but rather just clean it up as best as possible. I've used sodium percarbonate before, which was ok; but is there another product that is the bee's knees (along with scrubbing, of course...)? I was wondering about this oxalic acid-based cleaner: https://www.bunnings.co.nz/intergrain-4l-ultraprep-timber-cleaner_p1563243

Many thanks.

Before this thread grinds to a halt, any thoughts on the above?

concordnz

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#3118765 21-Aug-2023 19:56

I've used a bunch of different deck cleaners.

For 'heavy moss/gunk/previous stains.' I'd recommend "NakedStripper" from CD50.co.nz

Ive also used intergrain PowerPrep, & Cabbots Deck Clean.

Id rate the Intergrain PowerPrep (similar to the UltraPrep you linked to) as best for your decking.

concordnz

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#3118767 21-Aug-2023 19:58

mattwnz:
concordnz: Hardwood decking can be fitted a lot closer as it doesn't expand in the wet, like Pine does.

Although shouldn't it still have some gap? Are there recommended gaps for both pine and hardwood?

Yes, all decks should have gaps in them when fully dry.

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concordnz

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#3118815 21-Aug-2023 20:06

mattwnz:

I thought most people put the grooves on the underside, as it allows water to drip off the underside? I personally am not a fan of grooves on the top surface, as it reduces the surface area your foot is in contact with and can be slippery in the longitudinal direction, especially when it gets algae growing on it.

I did heaps of research into this when designing & building my Deck.
In short, 'both ways are right'.

Often in commercial installs or damp spots you will be required to put them grooved side up, for traction.

Some people also put them grooved side up for texture/look.

Others put them grooved side down because they like the smoother finish. (note, if painted, the smooth side up can get quite slippery when wet) - but if stained or left to silver off naturally, it's fine.

Bung

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#3118817 21-Aug-2023 20:12

The professional deck restorers that contributed to the Aus Renovate forum while it was running all swore by Sodium Percarbonate (cheapest Napisan clone available) in hot water.

jonathan18

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#3118828 21-Aug-2023 20:41

Thanks for the ideas re deck cleaners.

It looks like PowerPrep isn’t available in NZ at the moment, going by its absence from Intergrain’s website.

I can’t seem to choose between a product like UltraPrep or just getting a few kgs of sodium percarbonate off TM, especially when I read feedback like that in the post immediately above.

But for the specific areas where there’s mould (eg, under the shadow of a tree), should I use something specific for this, eg a mould killer like this one or an alternative product someone would recommend?

mdf

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#3118840 21-Aug-2023 21:26

Where does the water run off to? We had flowerbeds at the end of a previous deck and it quite significantly constrained what we were able to use. I'm pretty sure we ended up with one of the Bunnings concentrated deck clearner options, but had to do the version that you scrubbed on with a broom because it was less toxic to plantlife.

eracode

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#3118869 22-Aug-2023 01:56

@jonathan18 May I ask where are you based?

Sometimes I just sit and think. Other times I just sit.

tchart

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#3118878 22-Aug-2023 07:00

concordnz:

I be tempted to run a circular saw down the join between boards to open it up a little more to allow drainage between boards like it should have (keeping blade depth shallow so it only goes the depth of the top boards)

I have the same problem, the guy who built our deck was "too good" and the spacing is minimal. The gaps get filled with dirt etc and then block the water from draining. If the deck has been water blasted recently then I have minimal pooling.

What Ive found is that using a oscilating multi tool is a good way to clear the blocks without destroying the deck - as the side of the blade doesnt cut.

trig42

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#3118882 22-Aug-2023 07:15

jonathan18:

Anyway, while on the question of decks - what would people recommend as the most effective deck cleaner? I don't want to stain it, but rather just clean it up as best as possible. I've used sodium percarbonate before, which was ok; but is there another product that is the bee's knees (along with scrubbing, of course...)? I was wondering about this oxalic acid-based cleaner: https://www.bunnings.co.nz/intergrain-4l-ultraprep-timber-cleaner_p1563243

Many thanks.

We used the Wet and Forget product 'Hit the Deck' and it cleans the wood really well - takes some elbow grease as well.

The next time we did it, someone suggested that Hit the Deck is pretty much just Napisan, so we tried with that. Worked just as well.

Dissolve Napisan into hot water in a sprayer, spray liberally over deck and leave for a bit, scrub the part you've just done, rinse and repeat on another section. Wood comes up like new. We've done it on a pine deck and a kwila one, same results on both.

johno1234

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#3118891 22-Aug-2023 08:01

@jonathan18 are the boards screwed down or nailed? If screwed then lifting them is very easy if you have an impact driver. I would mark them first to make sure you can put the same boards back in the same spot the same way around. Whip them off, then ask around here for someone with a thicknesser or electric planer (or your local men's shed) to buzz a couple of mm off them and put them back down again. I would also chamfer the edges with a router. I would also put them back in with new screws to avoid any turned out heads or broken off screw risks.

This would not take long if you have the right tools, or be a PITA without the right tools. Great excuse to get down to the hardware store and purchase some tools!

Not sure about running a circular saw along the gaps in situ. It would be very easy to end up with some wavy or rough edges.

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