Repairing cracks on deck joists

Question

This year, being a beginner in handyman skills I decided to replace the deck boards and railings of my deck. When I bought the home about 1.5 years ago the professional who checked the house for me told me that the underlying structure is in good shape.

So, I started the demolition couple of days ago. One thing that's concerning me is after I removed the deck boards, I see the cracks on top of the joists especially where the previous screws went in with older deck boards. Rest of the joist looks good to me.

Now, do I replace the whole joist or can I do anything else to strengthen the structure ?

Note: My house is 17 years old. I'm assuming the current deck is at least 15 years old.

Answer 1

None of that is concerning. It's called "checking" and it's what happens when wood dries out. Look at the logs next time you're in a cabin. The screws tend to direct it and mildly exacerbate it, but it's not really a problem.

You could use flashing to protect the joists from water going forward, but for every joist you cover there's an unprotected connection or cut end or other vulnerable spot that will rot out eventually anyway. I'd install your new decking and railing and plan on another 10-15 years of service from the deck. Then it'll be time for a rebuild.

Answer 2

As others have commented cracks in joists are fairly typical. Holes from previous screws are also common. While these defects won't have an initial structural impact they can lead to premature failure by allowing water to enter joists and not drain out.

The best practice for deck joists is to use a flashing tape on top. Something like this:

https://www.amazon.com/DeckWise-Joist-Tape-Adhesive-Flashing/dp/B00VTVUSM4?tag=contractortalkconvert-20

I'd get some PL premium (not subfloor) adhesive, seal up the holes/cracks you could clamp the joists after putting the PL into them. Wait for that to cure and then use some flashing tape.

To give you a better feel for how compromised a joist can be here is a typical guideline used when notching or boring holes:

http://www.plymouthmn.gov/home/showdocument?id=4707

Answer 3

I would not do anything to the joists. Are you rebuilding because the screws have rusted ? If so, stainless screws last longer than the wood . Last year I refurbished my 22 year old deck, the main problem was the steel screws had rusted away. The joists were all good although some of the galvanized hangers had rusted away. I did go back with stainless and the few deck boards I replaced , I flashed with copper to slow the rot here in the TX rainforest.