Can you use glulam beams outdoors for a pergola?

[Andreas-sa]

Planning to build a pergola this summer and the span is about 5.8m. I want to avoid placing a post in the middle, so I need to find suitable timber that is 6 meters long. Glulam beams are available locally in that length, and I am also considering using glulam posts because they are dimensionally stable and do not warp.

Is it okay to use glulam outdoors if the wood is treated? Linseed oil paint or acrylic paint?

I was thinking of using Glulam beam 42x225 GL28cs and Glulam pillar 90x90 GL30h.

 

[fribygg]

Linseed oil paint or acrylic paint?

Acrylic paint is unsuitable for wood that is painted all around because the wood rots.

 

[Testarn]

Acrylic paint is unsuitable for wood that is painted all around because the wood rots.

I would rather leave it unpainted than have acrylic paint, but linoljefärg is a good alternative.

 

[Andreas-sa]

Acrylic paint is unsuitable for wood that is painted all around because the wood rots.

ok, so you should not enclose the wood but it needs to breathe?

 

[z_bumbi]

As for what is available locally, I would choose what I want without regard to the local selection and just order it home.

Admittedly, I would build a pergola with "roof" beams at that length, but that's a matter of taste.

 

[fribygg]

ok, so you shouldn't encapsulate the wood; it needs to breathe?

If you paint plastic paint all around, you can be sure it will rot faster than untreated wood. If you only paint one side like a facade, acrylic paint CAN work, but why take the risk?

In your situation, I would order regular sawn wood in solid dimensions and the right length; there are sawmills specialized in long timber, and if you want color on the pergola, then Falu red paint or tar paint, roslagsmahogny, or regular wood tar are what will work best over time.

 

[Andreas-sa]

If you paint with plastic paint all around, you can be sure it will rot faster than untreated wood. If you only paint one side like a facade, acrylic paint MIGHT work, but why take the chance?

In your situation, I would order regular sawn timber in sturdy dimensions and the right length; there are sawmills that specialize in long timber, and if you want color on the pergola, then distemper or tar paint, roslagsmahogny, or regular wood tar will probably work best over time.

Thanks, it sounds reasonable to go for regular sawn timber if I can find a supplier.

Anyone have tips on sawmills near Gothenburg? I will need 2 x 6-meter beams and smaller beams/timber for posts and cross slats, but maybe it's easiest to buy those at the building supply store.

 

[fribygg]

Derome saws long, not sure if you can shop at their facilities privately but all serious building merchants can order what you need.

 

[z_bumbi]

Glulam for outdoor use requires smaller dimensions than regular wood and is also easier to move around. With such a long span, the dimensions become very coarse anyway.