Old deck - advice needed

[lemerv]

Hi all,

My house is about 40yrs old. There is a second story deck (1.8m x 11m) that has a few spots where the planks are rotting (see photos).

I was going to replace them but after pulling them up I noticed that in a few spots the cross beams (right term?) are also rotting a bit. It appears to be only affecting the surface few mm (ie the cross bean feels solid otherwise).

Now I’m wondering whether I need to worry about the cross beams. Are they fine as is (eg maybe structurally a but of surface rot it fine, especially as planks are spread across many cross beams). Should they be replaced? Can they be braced or strengthened somehow? Or am I kidding myself and this is a sign the whole deck needs be assessed and and maybe professionally fixed/replaced?

Majority of the deck looks fine to me. It’s just a particular area that is more exposed to the weather that looks concerning. But utlimately I have no idea about decks so appreciate any advice.

Cheers

525270
The worst of them.

525271
Pretty bad

525272
Pretty bad

525273
Not too bad

525269
Underside of deck

525274
How cross beams attach to house

[jack620]

That definitely needs to be professionally assessed.

[Mountain Ash]

Hi there. The deck joists are hardwood and are beginning to show signs of rot. This will only get worse as the damage starts to hold more water, which leads to more rot, which leads to more water holding......I am sure you get the idea. The paint is probably hiding other damage too - was this house recently sold? This "trick" is often done to dress up a tired deck. Treated pine is a better replacement for the joists, using a flashing on top of the joists (like Protectadeck) helps as well. If you like the colour you can paint treated pine and possibly use matching composite decking. Hope some of this helps.

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[lemerv]

The paint is probably hiding other damage too - was this house recently sold? This "trick" is often done to dress up a tired deck.

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This is 100% what has happened unfortunately. We bought the place about 18 months ago. First home so wouldn’t have know to look for that but I’m surprised the building inspector didn’t pick it up. Anyway, such is life.

I’ll get someone in to look at it.

cheers

[jack620]

That's a disgraceful "trick". Second-storey rotting decks are a danger to the people on them and under them.
If that deck collapsed and injured/killed someone, the building inspector would likely be prosecuted. Sorry this happened to you.

[Skew ChiDAMN!!]

That's a disgraceful "trick". Second-storey rotting decks are a danger to the people on them and under them.
If that deck collapsed and injured/killed someone, the building inspector would likely be prosecuted. Sorry this happened to you.

As is, the damage isn't that bad and probably would be OK for a few more years... long enough that any inspector can wipe their hands of it. It is not a structural fault. yet.

However, as Mountain Ash stated, this is the beginning of the rot and is best treated now while you are aware of it and already have the deck partially disassembled. I'll second the use of flashing on top of the bearers; it's a cheap expense compared to how much extra life its' use adds to any deck and imo should be mandatory.

[jack620]

As is, the damage isn't that bad and probably would be OK for a few more years..

Big call! :oo:

[lemerv]

How would you treat it?

[rwbuild]

How would you treat it?

You treat it by totally removing the affected piece and replacing with new.
I would be very concerned about what is going on behind the cladding (inside the wall). My experience with this type of construction is that water DOES wick back into the wall area and judging by your photos there has been liberal use of gap filler to make it look good

[Marc]

Hi Lemerv ... I have demolished and rebuild my fair share of decks.
They all looked like yours, hardwood deck boards hiding deep rot in the treated pine joist.

No point replacing the boards, since there is no good hold for the screws. In fact those boards under cover will probably last a while longer, until someone puts his foot through a rotted board.
Sure, the joist will not collapse tomorrow. Small consolation.

Can you take pictures of the state of the cross beam? If that can be salvaged, you are doing well. The rest unfortunately needs to go.

Another point of concern as stated by others is inside the wall that supports the joists at the proximal point. Any chance to have a peak in there?

When you rebuild, spend that little bit extra and use protectadeck, a strip of rubber over the joist and beams that stops the water pooling.

[419]

The damage you can see on top of the joists (usual building term for the beams you mention) gives you no idea of how deep it goes, nor whether it is the same or worse in other parts of the joist. Stick a screwdriver into the worst bits and you'll probably find it goes deeper. When it gets to the stage in your pictures the structural integrity of the joist is already less, maybe much less, than the original specification. For example, a 200mm deep joist that rots out the top 50mm or so is maybe a 150mm deep joist which is well below the size needed for the original span. That assumes that the original specification was correct, which often wasn't the case 40 odd years ago when there weren't the same engineering standards as nowadays. Decks then were often built with ordinary builders hardwood joists and in case I encountered rapidly rotting oregon with T nailed hardwood decking, frequently installed upside down with the draining reeding on top for grip, which just accelerated the rot underneath with the flat faces of the joists and decking trapping water and rusting out the thin T nails even faster than they would have managed just by water getting down their sides.

I couldn't agree more with the comments by jack620 and rwbuild.

Note particularly rwbuild's comment about what's going on behind the cladding, which might be as big or even bigger problem than what you can see. For all you know some idiot has just nailed the deck joists to the side of studs (vertical framing timbers for house) instead of a proper support and it's all been quietly rotting as water seeps in for the past 40 years, which also affects the structural integrity of your house frame.

There is no warning when defective decks collapse.

Unless you're in one of the prime suburbs, and maybe not even then, the compensation to anyone seriously injured and certainly if killed will probably exceed the value of your house, and there's a fair chance that somewhere in your home insurance policy there will be a clause that says claims will be denied if you fail to maintain the building properly or don't meet building standards. And insurers will always refuse any claim which has the slightest prospect of success, and leave you uncovered and or spending years of money and anxiety funding lawyers to fight the refusal of cover. https://www.couriermail.com.au/news/queensland/balcony-death-family-to-sue/news-story/d0844c10e6cf0a995d19329b6d8d6c03 Or you could just kill or permanently disable one of you kids, and see how you feel about that for the rest of your life.

It ain't worth the risk. Demolish the deck or get a new one professionally designed and built.

Sorry to sound alarmist, but I've done enough deck repairs or perhaps more often just declined the job because the home owner won't pay to get proper engineered specifications because "Mate, it's just a little deck. It's not like I'm asking you to build a house.". And we all know who is going to be sued if the deck I build fails.

[419]

They all looked like yours, hardwood deck boards hiding deep rot in the treated pine joist.


Joists in OP photos look more like hardwood to me, as does the rot.

The rotted deck joists that look like the OP's pictures I've encountered have always been old hardwood from about 20+ years ago.

Although the pressure treatment in treated pine doesn't penetrate all that far into the timber, it seems to work well enough close to the surface to keep rot out, certainly at H3 CCA. Conversely, I've found H3 LOSP pine unsatisfactory on the basis of repairs I've done on exterior timber like door jambs and window sills that have been exposed for no more than about 5 years in fairly new builds. I wouldn't use LOSP for anything.

The problem I've found with older CCA treated pine in thicker dimensions like deck joists, as in 15 to 20+ years ago, is that often it's not stable and perhaps was installed wet out of the pack, so it moves and twists under the decking causing an entirely different set of problems to rot, and which can't be corrected as the timber has set in its altered position.

[jack620]

The damage you can see on top of the joists ....

This post absolutely nails it (pardon the pun). It's been a while since lemerv's last reply. I'm curious to know what his plan is for the deck.