Wherever water is slow to evaporate. Might be where the stringers meet the ground, the joint between the riser and tread, the underside of treads, or nail holes on horizontal surfaces.
Yes, weather is hard on untreated wood.
gfgf
Most often where the wood meets the soil. Heavily shaded, or poorly drained areas will also hasten wood rot
Top of the handrail
All of the above, but most commonly found at the bottom of the stringer where it sits at ground level slurping up water.
The amount of time it would take for outdoor furniture to rot depends on the outside environment. Often hot humid places rot wood more quickly than others.
yes you should waterproof it but the wood will not last as long as usual because outdoor carpet holds water and will rot the wood in time.
When choosing outdoor decking material you have two options wood or synthetic decking. Some wood are lesssusceptible to rot. Synthetic materials are made from recycled products. Synthetic is usually maintenance-free, the wood will need stained and upkeep.
Decomposers cause wood to rot.
Wherever they are screwed or worse nailed. Nobody seems to use proper weatherproof coated screws. I have renewed dozens of outside steps that would have lasted 10 years more if only they had used proper nails or screws that wouldn't rust and cause rot.
Rot is found wherever water or damp can get to wood. Also in many constructions, where people have used plain steel nails or screws, rather than coated ones.
Wood can be treated with various preservatives to prevent rot and infestation.