Half lap joints on deck boards

Afternoon all,

Got a small deck (5m x 3m) out the back which is starting to show signs of rotting. One board was rotten so I’ve temporarily replaced it, but also noticed that the bearers are also nearing the end of their useful life.

Anyway, when pulling up the board I noticed that they had lapped the boards when joining over the bearers. Is this common? Seems like a lot of work. When I did the other outdoor area under our patio I just cut em off square and screwed. Prob not hard to do with a router jig but I can’t see any benefit.

Cheers,

Tom


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The builders and/or carpenters can answer the why of it, but just thinking about it, I imagine it would keep the two boards at the same height as each other and not create a trip hazard like individually secured boards can (you know how one can work its way up and the other stays still). If you do repeat that then you can use Sikaflex Pro in the joint to keep water out, and in any case make sure the end grain is covered with a skin of Sikaflex (lapped or not). Rot usually starts at the end of the board eh? Keep the water out, keep the board. SP doesn't set hard, but stays rubbery so it will move with the deckboards.

To mitigate rot in the joists/bearers you can put down a layer of ProtectaDeck (between joists and bearers and deckboards and joists).

I’m not a carpenter or builder, but the first thing that came to mind.$$$$$$.
I’ve build and re decked a few decks in my handyman company, and no way could I compete on price if I was doing half laps on the joints.
But I agree with Brett it is a good idea, but just a time sucker.

Cheers Matt.


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There is no reason to do it apart from you can maintain your screw lines on joined boards the same as the rest which is a nice detail if you can afford the time or $$$$ but as mentioned you need to keep the moisture out for longevity

Thanks, appreciate the response. Now just got to decide what timber to replace with!!


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