I am building my first deck and am almost done with the frame, but I'm starting to doubt my construction, and I need a bit of input on what I need to improve.
The deck is 12 x 3.7 meters and is placed on concrete slabs. 120 mm joists on a 60 cm center which will have 28x145 decking on top.
Now I'm starting to doubt, and there are a couple of things I'm worried about.
1. Span
Right now there are 3 support points, so the span of the joists is about 150-180 cm. The tables I've read say that the span for 120 floor joists is 190 cm, but that's for a beam, so I'm not sure how to think about it when it's on slabs. Is the span of the 120 joists too large, and how do I best solve this?
2. NTR AB vs NTR A
Before starting the construction, I was unsure how deep I could go, so the joists are 45x120 NTR AB. The framework is about 10 cm above the gravel. All joists against concrete have tar paper. I have now understood that you should have NTR A in the framework and ground-level construction, so is NTR AB actually wrong and what can I do to reinforce potential rot resistance? I don't want to have to replace them in the next 10-15 years.
I also have some "ventilation channels" that I've replaced since the old ones were rotten, but they are made of regular decking that I wrapped with tar paper. I can imagine they are a bit more exposed.
Is there something to keep in mind when placing the tar paper, e.g., I've folded it around like an L on the joist against the foundation, but could that potentially trap water?
The deck is 12 x 3.7 meters and is placed on concrete slabs. 120 mm joists on a 60 cm center which will have 28x145 decking on top.
Now I'm starting to doubt, and there are a couple of things I'm worried about.
1. Span
Right now there are 3 support points, so the span of the joists is about 150-180 cm. The tables I've read say that the span for 120 floor joists is 190 cm, but that's for a beam, so I'm not sure how to think about it when it's on slabs. Is the span of the 120 joists too large, and how do I best solve this?
2. NTR AB vs NTR A
Before starting the construction, I was unsure how deep I could go, so the joists are 45x120 NTR AB. The framework is about 10 cm above the gravel. All joists against concrete have tar paper. I have now understood that you should have NTR A in the framework and ground-level construction, so is NTR AB actually wrong and what can I do to reinforce potential rot resistance? I don't want to have to replace them in the next 10-15 years.
I also have some "ventilation channels" that I've replaced since the old ones were rotten, but they are made of regular decking that I wrapped with tar paper. I can imagine they are a bit more exposed.
Is there something to keep in mind when placing the tar paper, e.g., I've folded it around like an L on the joist against the foundation, but could that potentially trap water?
