ᐅ Patio substructure made of wood – weather exposure

Hello everyone,

Our terrace (about 38 m² (409 sq ft)) will be located above our garage driveway, basically on the first floor.
We have a steep slope, so the basement is planned with a double garage and the terrace above it. It will be accessible from the living areas.

Now to the main concern. The main substructure from the timber construction company for the terrace/carport will be wooden beams. On top of that will be Northern Pine with resistance class 1. The "smaller" substructure will, of course, be made from the same material: 45x70 mm (1.8x2.8 inches) squared timber. Then the decking boards will go on top.

So there are 3 layers of wood stacked. The decking boards plus the smaller substructure will be mounted in the classic way using Terrafix spacers and should not need to be replaced for hopefully 15+ years.

QUESTION: How can I properly and weatherproof attach the squared timber substructure to the beams? A friend of mine had severe rot develop deep into the beams at the screw points. I don’t want to have to completely replace the beams in 20 years, but rather hopefully only one maintenance cycle later!

What solution would you suggest? The timber center also offered me rubber granulate pads. Should I use those? Are they sufficient?

Thanks a lot for your advice!

Konstantin

Pine (including thermo-treated pine) will never achieve durability class 1 (resistance class 1). If your supplier claims otherwise, don’t trust them! Class 1 would be, for example, teak or ipe. Thermo-treated pine would be at best class 3.

Regarding the durability of the structure:

- Ventilation
- Roofing or covering
- Aluminum instead of wood for the substructure

The pads would at best protect the small substructure. It shouldn’t hurt to use them and they cost almost nothing.

Dr Hix schrieb:
Pine (including thermo-treated pine) will never reach durability class 1 (resistance class). If your supplier claims otherwise, you can disregard that! Class 1 would be, for example, teak or ipe. Thermo-treated pine would at best be class 3.

Regarding the durability of the structure:

- Ventilation
- Roofing/covering
- Aluminum rather than wood for the substructure

The pads should at best protect the "small" substructure. But they probably won’t harm and cost almost nothing.

Hello Dr Hix,

thank you for your response. Nordic pine contains a silicon compound and is compressed under high pressure, essentially petrifying it. This resulting mineralization makes the pine more durable. I am opting for this product because I prefer this silver-gray color, and teak or similar woods are not an option for me. It’s also a relatively new product on the market. At home, we have teak, so I am familiar with that wood on the terrace.

Back to the substructure: it is sufficiently ventilated! Also, the terrace faces south/southwest.

Unfortunately, the subfloor for the terrace, above the garage entrance, must be made of wooden beams. Do you mean placing the pads on the wooden beams and then screwing the substructure onto the pads? Is that correct? See attached sketch.

Would it not be possible to lay the entire substructure and decking floating on top of the entire beam structure?

Thanks and regards

We often build piers at harbors. Here are a few tips for the substructure to ensure long durability. Get Carbolineum. It can be found at building material suppliers. Use it generously, really thoroughly, on both the beams and the lower battens. For the pads, which are very important, use pieces of roofing felt. If you can manage to get genuine Carbolineum from an eBay shop, that is definitely preferable. When applying it, please wear gloves and safety glasses.

Nordlys schrieb:
We often build piers at harbors. Here are a few tips for the substructure to achieve long durability. Get some Carbolin. It’s available at building supply stores. Use it generously, really generously, on both the beams and the lower battens. For pads, which are very important, use pieces of roofing felt. If you can somehow find genuine Carbolineum from an eBay shop, that is clearly preferable. But if you do, please apply it with gloves and safety glasses.

Hello Nordlys,

thank you for your tip. Is the Carbolin only available in brown, or is there a white version as well?
If it’s only brown, then I can only treat the top side of the beams, since the rest is white.

I will take a closer look at it.

Carbolin is always brown-black. Why is that—because the substructure is visible?