[barmaley]

Hi,

I just found out that many of my deck's joists developed some cracks that seem to be related to the top boards nailing. Should they be addressed?
What if I decide to replace the PT boards with composite ones and use hidden fasteners? Will the screws hold considering the cracks?

Thank you.

 

[Fix'n it]

mine did that to. i don't see it as a imminent problem. but, it will allow more water in, so the wood will now last as long. had i known, i would have put something on top of them first. but, they probably will outlive me, so i am not concerned.

 

[kwikfishron]

It can be a problem and I always bring this up when someone ask me about just replacing just the decking on an old deck.

The split is caused by the old fasteners and you’ll likely problems with many of the new fasteners not ‘grabbing’ as a result from it. PT lumber likes to rot from the inside out and yes water can get in there which is not a good thing.


For those that won’t even consider the possibility of replacing the joist I’ll suggest adding a 2x4 to the side of the joist as a nailer. And for those that won’t even consider doing that I’ll just pass on the job because even after the warnings who do you think they'll be looking for when they start having problems with some of their brand new deck boards start lifting.

 

[joecaption]

"It can be" that's the key, Until the deck boards are removed it's hard to tell if it's normal checking caused from uneven drying or the joist are truly starting to rot out.
If it was the old fasteners causing it why would the splitting not line up with the fastener, and why would there be two splits?
What's your joist spacing? If it's 24" O/C your going to have to install more joist, most composite needs 16" O/C or you'll end up with a wavy deck.

 

[barmaley]

Thank you all for your replies!

Great idea about the 2x4 nailers, kwikfishron! How would you attach them to the joists? Is there any code requirements for those?

I have 16" O/C, joecaption. I do not have immediate plans to replace the original boards since they are in a good shape. Is there a way to rule out the rotting without lifting the boards? Something like poking the place with sharp metal stick? Will it help to try to put some wood filler over visible parts of the cracks as a temporary solution?

Thanks!

 

[bcemail]

How old is the deck? Will you be putting composite on soon? For the most part, PT lumber cracks and checks, but is still solid. I'm replacing the boards on my deck that's about 15 years old (I think). Plenty of cracks and splits on the joists but they are still solid. I'm covering them with joist tape to help seal them from any future damage but only a couple have needed additional boards attached to give a better surface for fasteners.

 

[barmaley]

I will try to maintain the deck for a few more years before putting new boards. The deck is 7 years old.

 

[Gary in WA]

I really doubt the fasteners are causing your checking splits from drying. The PT is infused with the chemicals/minerals and really heavy due to the wetness. I've seen the same checking on joist pieces without any fasteners ever used... don't use a filler. They should have been water-proofed (PT is not water-proofing) or a membrane added on the joist tops before the decking installed... appears the 5/4 boards were installed with air pressure too high hence the fasteners below surface hiden by wood filler.

Gary

 

[ChuckF.]

Next deck I build is going to have a 1-1/2" strip of flexible sticky flashing on the top edge of all the joists, spots where a joist butts into a beam, and the ledger and the top of all posts. I also plan to avoid doubling up any 2x wood without spacers between them.

You have to think about all those places that take a long time to dry out after a rain.

 

[barmaley]

Sure the joist tape is the right solution but unfortunately the builder did not use it. I guess it is not required by the code so I cannot ask the builder to fix it. I will put the tape when I replace the boards.