I am building a roof over my patio. The roof is supported by four posts at the front. The posts consist of laminated wood 115x115mm and they primarily rest directly on the foundation blocks (with roofing felt in between) but are also notched to get support from the front beam, which also rests on the foundation block.
The posts are painted with Beckers window paint plus, which according to the manufacturer is suitable for items that are painted on all sides. The ends have also been primed with oil.
I thought the roof overhang would protect the posts well from rain, but I have now discovered that this is not the case and they get wet almost every rain shower.
I am now worried that my posts will rot and that I should have chosen pressure-treated posts instead… I have invested a lot of work and money into this and am afraid I have made a big mistake.
With that fastening at the bottom, it doesn't look optimal.
You need to ensure that there is no standing water/moisture at the bottom that the posts can absorb.
There is a risk of moisture damage, yes. It's good that you have placed tar paper in between at least. The laminated beam is made of spruce, so oiling doesn't help much. Spruce has closed cells and does not absorb oil. It stays on the surface and protects. So it's important to maintain the transition between the post and the flooring. I have built the same way myself but with pressure-treated laminated beams that have been painted.
Nothing has eternal life.....just build on and maintain it as you go. In 15-20 years when it's very decayed, maybe someone else will have to take care of it anyway.........
It is not good to have a thin gap between two wood pieces! It's perfect for water to seep in through capillary action and stay there. It is better to have a gap of a few mm and use spacers to set posts on, that way the end grain can dry quickly after rain.
The important thing with regular glulam (spruce) outdoors is that it gets a chance to dry out and does not have standing water after a rain shower. It can withstand rain if it is painted, but not standing water. The risk for you is the standing joint between the framework and the post. That's where the water gets in and has a hard time drying out.
Consider whether it's worth redoing with pressure-treated posts. Pressure-treated glulam doesn't seem to be entirely uncommon in northern Sweden. Here in southern Sweden, it is almost impossible to get when I bought Martinsson and Moelven (wholesalers) can deliver to the trade.
It's the end grain of the post that's the weak point, and it's difficult to maintain since it's against the plinth and bearer.
Not very fun to have to redo it, but I'd rather do it now before the railing is screwed into the posts...
The crucial question is how much better a pressure-treated post is compared to the current solution. How many years does it extend the lifespan by? Hard to answer maybe, but is it marginal or significant?
If I redo with pressure-treated posts, should I make any other changes or proceed in the same way?
But what time frames are being discussed? People have built with regular timber for ages, both in good and bad ways. It's not like it becomes unusably rotten in just a year directly.......
But what time frames are we talking about? People have been building with regular lumber for ages, in both good and bad ways. It's not like it becomes unusable in just a year.......
It's the time frames I'm asking about, i.e., how many additional years I would get with a treated post. If it's marginal, then there's no point in redoing it. But I suspect it might be more than marginal in this case?
It's not a pleasant feeling to build something knowing you've made a mistake that will mean you "soon" have to redo it.
Having to replace the posts in 5-7 years when the railing is up doesn't seem so appealing.
Consider if it's not worth redoing with pressure-treated posts. Pressure-treated glulam doesn't seem to be uncommon further north in Sweden. Here in southern Sweden, it was almost impossible to get hold of when I bought Martinsson and Moelven (wholesalers) can deliver to the trade.
[image]
I called my local building supply store and they had pressure-treated glulam posts 115x115 in stock and I got a good price so I went for it! Hopefully, it will give me a few more worry-free years with the deck.
Now I need advice for painting. Is the rule to wait a year before painting pressure-treated wood the same for glulam?
Should I paint the entire post including the end grain?
Type of paint?
Thanks to everyone else in the thread who helped me reach a decision. It's a shame to have to redo it but it feels good in the soul.
I'll have to see if I use the same construction/fastening or combine the treated posts with some form of shim or similar.
I don't think any of the post shoes linked above will fit or stand steadily as the plinths are a bit uneven on top.
I have primed with indstriprimer, like Caparol's Unigrund or Biltema's snickerigrund. This grips the wood well. It has lasted for 25 years on the oldest treated woodwork I have painted. Probably stronger impregnation back then, but the principle is the same. What you paint on the primer matters less. Choose the same type of paint as the house. The treated laminated timber posts are already dried out and should be able to be painted directly. Wipe them with a solvent, like white spirit or denatured alcohol first. There may be "greasy" residues on them.
I have primed with indstriprimer, like Caparol's Unigrund or Biltema's snickerigrund. This grips the wood thoroughly. It has lasted 25 years on the oldest pressure-treated joinery I've painted. Probably stronger impregnation back then, but the principle is the same. What you paint on the primer is less important. Choose the same type of paint as for the house.
The pressure-treated laminated timber posts are already dried out and should be possible to paint directly. Wipe them off with some solvent, like turpentine or denatured alcohol first. There might be "greasy" residues on them.
Okay, I have some "Beckers Primex Trägrund" left over but I might get a better primer.
Do you recommend that I paint every side including the end grain on the laminated timber posts where water might stand, or is there a part that is better without paint?
