The stain contains oils which penetrate the timber surface. This protects the surfaces rather than allowing it to deteriorate. Paint is a protective surface on the surface of the timber. Un-oiled they will deteriorate slowly rather than rotting. Rotting is caused by being damp for extended periods (regularly for months, years, etc.). Some timbers are better than others for outdoors. Treated pine (H4) will last for years in the ground. Untreated un-oiled pine not long at all. There are many old farm sheds that are clad in untreated & un-oiled timbers and they're still surviving. I've seen many old decks that need decking boards replacing due to being left un-maintained. A deck area has little protection from the elements so needs continuace maintenance.

Thanks. So, you could have access to a external tap garden near by? You could put some small irrigated vertical gardens in this space and plant out some grasses or low growing or cascading plants. This option will require some thought to the wall structure and allow the water to drain away and keep the wall space relatively dry. The other could be (the photo is not good to see) run horizontal wires internally in a set spacing you desire on the timber cladded wall. Then, plant outside in that corner (in ground or in a large pot) and grow a climbing plant (star jasmine or similar) and train it to grow on the wires you set inside that space. This will tone down some of the hard materials and add some softness... Just a thought!

If you can put doors on the whole back area and deck or pave out to a functional size for entertaining - be sure to have as close to same height as inside and the whole width of the house if possible. You could do the pergola which looks gorgeous and makes a cozy feel. On top of the pergola you may be able to do a weatherproof retractable awning if you do not want a permanent covered area. That would make a whole area for indoor outdoor entertaining in all types of weather. You can still have a step down area to grass and plants at the rear. Travetine is great and easy to hose down. You do not have to concrete them down use pavers on a good road base. You would have to speak to the experts about how to get the right height - also be sure to have a slight fall away from the house.

Hi Love the setting! From what you are describing, it sounds like you have a ventilation issue. A deck lower than 400mm off the ground needs to have ventilation just like the house. This typically means the sides are open (doesn't happen) and the spacing is around 5-6mm between boards. If you don't have this, the water that gets in cannot evaporate and will keep the ground and the underside of the deck moist, even with your drainage as it can pool in sections. This in turn means your deck is always wet. Once that happens, it is only a matter of time before fungus growth/soft rot etc occurs. We always excavate a low to the ground deck to ensure we have 400mm of clearance to the underside of the bearers. Another way is to ensure there is a moisture impermeable membrane across the ground (plastic) covered with gravel and graded down with vents placed all around. Cheers