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Best way to seal Rough Sawn Cedar for Outdoor Use?

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Forum topic by wilschroter posted 06-24-2019 03:35 PM 424 views 0 times favorited 16 replies Add to Favorites Watch
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wilschroter

83 posts in 947 days


06-24-2019 03:35 PM

I’m making some faux wood beams out of rough sawn cedar for outdoor use. Any suggestions on what I can do to protect the wood from the elements, especially because I’m going to be joining them with 45 degree cuts at the seams. I’m worried about them warping/separating over time.


16 replies so far

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clin

1041 posts in 1418 days


#1 posted 06-24-2019 05:25 PM

I like Penofin for exterior natural finishes. It’s mostly an oil. It has great UV resistance. But like ALL natural oil type finishes, it will have to be maintained. Usually a fresh coat every year or two if it is directly exposed to the sun.

However, I don’t think there is any finish that is going to do what you want. Nothing short of exterior paint is going to be very good at actually keeping out moisture.

If I understand you correctly, you’re looking at wrapping boards around a structural beam and joining this with mitered corners. It’s hard to keep mitered corners like this tight in the best of circumstances. I think it would be borderline impossible in this case.

From your other post, I assume these are the 18” wide ceder boards you were looking for. Over that width, the boards will cup quite a bit. There’s really no way around that short of using quarter sawn boards, and I suspect that is pretty much going to be impossible to find in that size.

I’m no expert on faux beams, but have some experience with ceder in exterior applications. No matter what, the board’s moisture content is going to vary a lot. Certainly with seasonal changes and just week to week with weather patterns. So the boards are going to cup and change all the time.

Even without any constraint on individual boards (no attachment points), the boards will split here and there. Obviously the quality of boards is a large factor in this. But being tightly joined at the corners probably assures this. Even if you allowed the entire box formed by these boards to float around the structural beam. As the boards cup, either a tight joint will split, or the boards will.

I’d consider a design where the corners are butt joints. Maybe have the wide board extend well past the narrower board. This would draw attention away from any gaps, and actually hide the gap to some degree.

There are of course other ways of trimming the corners to hide the joint. And I understand this will not look like one rough-hewn timber.

While faux beams with mitered corners are done, I think this is much less likely to succeed in an exterior application with very wide boards.

-- Clin

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wilschroter

83 posts in 947 days


#2 posted 06-24-2019 05:29 PM

@clin this is great advice all around and mirrors where my head was at. I’ve reduced the size of these to 12” versus 18”. I was planning on using tightly mitered 45 degree joints, but something tells me this is going to end poorly, especially in Ohio where we have very big swings in temperature.

I was planning on using a poly coat over the whole thing after I stain it. Any reason I’d want to avoid that assuming I’m OK with the look?

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therealSteveN

3116 posts in 996 days


#3 posted 06-24-2019 05:44 PM

They won’t require any form of treatment to last a long time. You say beams, so my thought is an overhead beam. If this is in an open area where rain can fall into the beam, close the tops to prevent them filling even partially with water, as long term contact with water will hasten their demise. Likewise being off the ground to eliminate ground contact will help. just exposed to the weather where water can easily run off they will last many years.

untreated they will gradually turn to a gray weathered look. If you want them to stay fresh and reddish, you will have to use some high $$ finishes, or apply low $ one’s frequently.

In terms of construction of the beams I have seen many more done as these 2 show, either simply boxed, or boxed with an end cap. 2 reasons, easier to do, and Cedar when exposed to the elements may not rot next week, but it has a tendency of moving, usually this movement is at the edges, so a mitered board will have a much thinner edge, and will have more frequency of movement, so you will have gaps. At least more than the box builds.

If you want to go with the mitered corner you best bet is to use spacers inside like shown here, but on both the top of the beam, acting like a spreader, but also at the bottom so the miter can be nailed into the spacer. I would place the spacers at least every 2’ for a 4” beam, probably closer of wider beams.

I had typed most of this up, tried to post, and got that warning the web page had stopped working, When I got back to it, clin had responded, and you had said 12” wide. I would definitely use spacers on any of the beam forms I posted pics for, or you will have quite the wiggly beam, and your miters will open almost as sure as the sun comes up. I personally would use a spacer every 1’ of running length, they need not be special, just a wooden spacer to abort the woods wanting to twist and cup. 2×2’s are perfect for this. Just make sure if you use a chop saw that you set in a spacer block, so they all get cut eggzactly 12” or whatever you choose to go with. I would warn not to go less than 18”

proof of that nailing sequence is easily borne out if you see a house with cedar fascia’s, get underneath and look up. Keep in mind trusses at going to be generally 24” apart, so they will emphasize this a lot, but those fascia boards are NOT gonna be straight. Rather a continuous cycle of a dogs hind legs. If you like that look for a beam??? Yeah, didn’t think so.

-- Think safe, be safe

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wilschroter

83 posts in 947 days


#4 posted 06-24-2019 05:48 PM

@therealSteveN That’s great advice. I’d really like to try for a tight mitered corner to make it look like one beam. I was planning on building out an entire interior box out of 3/4” plywood to prevent as much cupping as possible. A little bit over-engineered but I would really like them to last. I have to build 8 of these bad boys, so it’s a lot of effort no matter what I do. Also, for what it’s worth, I”m planning to build 4 sided beams since they are visible on all sides.

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clin

1041 posts in 1418 days


#5 posted 06-24-2019 09:32 PM

Concerning the finish, are these exposed or under a roof? That makes a huge difference. If you coat it with poly AND it is exposed, I’m not sure that will hold up well over time.

One of the LJ members, John, has or had a sign business and hopefully will chime in on this. I know he has on other outdoor finishing projects. He seems to have a lot of experience with wooden signs and finishes.

I still don’t think any amount of trying to hold the wood flat is going to work. The wood will want to move, if you try to hold it flat, it will just split. The exception to this is veneers. Where they are thin enough that they have little resistance to being held flat. You’ll notice that Steve’s last photo above is a plywood box, with moderately thin exterior wood. Plywood of course is very stable. Though for outside, especially if exposed directly, you better use marine grade ply.

I also second what Steve said about the finish. An oil type finish won’t make the wood really last longer, but it will keep it looking fresh rather than the weathered grey look. just depends on what you want. Though if exposed to a lot of sun (like the desert southwest where I live), the finish may help the wood last longer. Strong sun will breakdown the wood and it will gradual erode. A UV resistant coating will slow this.

-- Clin

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wilschroter

83 posts in 947 days


#6 posted 06-24-2019 09:45 PM

@clin I’m not 100% sure, but my limited experience with veneers means a textured surface that is very shallow right? Meaning it’s not going to be able to get that good rough sawn look that (deep crevices) that I can get with cedar.

It sounds like no matter what I do, cedar is going to fall apart on me in some way. That’s unfortunate because I was really excited about using it.

Any suggestion for the next best choice in veneers?

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Lazyman

3568 posts in 1809 days


#7 posted 06-24-2019 10:06 PM

You don’t want to use thin veneers exposed to weather. I think that it’ll just peel up and crack unless you treat it like they do veneer on boats for example—cover it with fiberglass and epoxy.

I think that we may need a little more information about how these beams will be used. I don’t think that you said how long these are going to be and if they need to support any weight at all other than their own. A 12” wide beam sort of implies a pretty long beam. I assume that since you called them beams, they are horizontal? You say that they are visible from all sides, which sort of implies that they are vertical, or are they horizontal and visible from above?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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wilschroter

83 posts in 947 days


#8 posted 06-24-2019 10:11 PM

Here is a photo of the beams (columns) I’m going to replace. They are the cylindrical ones. They are about 8 feet tall and 12” wide. So they are going to run vertically. As you can see, they have a bit of protection from the soffit above but this is Ohio and they will also be submerged in snow at some point!

These are not load bearing at all – completely cosmetic.

They will get a fair amount of sunlight, but again, it’s Ohio, so we’re not overloaded with sun. My main concern is moisture. I’d like to use a really nice rough sawn looking beam to create a very heft footprint. I’m going to have metal brackets made at the top and bottom to separate them from the ground/ceiling.

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Lazyman

3568 posts in 1809 days


#9 posted 06-24-2019 10:37 PM

Since it is vertical and has some protection from the weather, you can simply use a decent quality stain of whatever color your want. Water will run off and not cause any significant problems as long as you have a good structure underneath the surface boards If you are trying to match the existing color you can paint it. If you want a wood post look, use a semi-transparent stain for greater UV protection.

As for construction, I believe that what I would do is use 2×2s at each corner to nail your mitered face boards to. Add some braces between the 2×2s every 2-4 feet to strengthen it . Basically construct an open box with 2×2s with some lateral support to make it rigid and attach the 1×12s to the outside Note that it may be a good idea to use stainless or aluminum siding nails, especially with cedar to prevent dark stains from the reaction with iron nails.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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clin

1041 posts in 1418 days


#10 posted 06-24-2019 10:51 PM

Definitely columns not beams. Not that that changes things too much. Though under the eave, and being vertical they are much less exposed than horizontal beams.

Looking online, these seem to be commonly called porch posts. And it seems to be somewhat common to have natural cedar posts/columns.

There are lots of photos of people doing this. But, not surprising, these are all images of newly finished projects. I really wonder how these will hold up over time. Painted I understand, but these more natural finishes just won’t keep the moisture out. Still having a hard time believing these will stay flat without splitting.

Though certainly Ohio is much more humid than where I live (New Mexico) and perhaps the generally higher moisture level keeps the wood more stable. Certainly the wood will stay closer to the freshly milled moisture content in a more humid climate. Where I live, even kiln dried wood, dries out MORE after being put outside.

Either way, I didn’t see any photos showing mitered corners.

Larger cedar timber posts are a thing. Maybe just get some actual 12”x12” timbers. Heavy and I’m sure expensive, but if you want a solid timber look, maybe just get the real thing.

-- Clin

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wilschroter

83 posts in 947 days


#11 posted 06-25-2019 12:10 PM

@clin Is it the case that no matter what I do, these boards are going to warp/cup/split? If that’s the case, is there another rough sawn option (other than cedar) that I should be considering?

@Lazyman I was thinking the same thing regarding the construction. I had built some of these for an interior project that was a bit smaller (8×8) and used a 1x strip along each corner and dropped a 1” screw inside the columns every 8” along the 10’ stretch. Held beautifully.

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therealSteveN

3116 posts in 996 days


#12 posted 06-25-2019 01:01 PM

Where in Ohio? I’m between Dayton, and Cinci. I source my Cedar up in Dayton at Requarth. I understand what clin is saying about WRC cracking, and splitting. I still don’t understand the why, but the stuff from Requarth behaves better than any I have seen before. Plus if you wanted to just replace those posts they would have them, or at least could get them. Possible there are places like them scattered over the state. I only know of them.

99% of the good stuff isn’t on their website either, you need to call the desk to inquire. 937 224 1141, ask for the lumber desk.

As far as the beams and miters, see if you can find them anywhere, and see if 99% of them aren’t like the ones in the middle picture. It works, is why guys do them like that. I’ll disagree with clin in that using the spacer blocks it gives you all that many more points of attachment, and you can control how much the cedar moves. I still would shy away from that thin edge you would get with long miters though.

I had every framer, siding Man, and home builder, repairman that had anything to do with Cedar, or cedar siding buying from Requarth. Guy who lived across the street from this house I built for my Wife, and I, was a home builder also. He got interested in “my cedar” after coming over to peek at the place during construction. “It doesn’t have any splits”......Anyhow he started buying from Requarth, and after a while everyone else up there did too. The guy who owned the lumber place in Troy Ohio wouldn’t speak with me. Supposedly I had cost him a lot of business. I always figured he could buy good quality cedar, same as Requarth did?

The old place, exterior was all cedar siding. I can’t say it didn’t have any splits. After 2 years it showed 4, when we left 21 years later it had 3. I replaced what I felt was a big one. In all I built 19 homes in Miami Co through the years we were there, all of them had some of that cedar on them, if not the entire house. Can’t even remember how many siding jobs I did. Splits, checks, and cracks were minimal. Still not sure what was different, I have to believe there are just different grades of cedar?

-- Think safe, be safe

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wilschroter

83 posts in 947 days


#13 posted 06-25-2019 01:38 PM

@therealSteveN that’s all great feedback and much appreciated. Any sense for what Requarth is sourcing that other shops (not talking about big box) can’t? I’m just curious on that front.

I’m going to build these columns with a custom fabricated metal header and footer that will wrap the top and bottom and then allow for a flanged attach point on either side. The nice thing about that is that in the extreme, I could remove the whole unit fairly easily and swap out wholesale if need be. The downside, of course, is that it will almost certainly not match the others given just natural weathering. But at least I’m a touch less “committed” permanently.

What I’m thinking about is whether or not building a plywood box behind the cedar would at least allow me to use a combination of glue and screws (from the back) to hold it steady to the surface. Any thoughts there? I know that if the wood wants to give, it’s either going to warp or split, but perhaps I can give it a little resistance?

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Robert

3441 posts in 1903 days


#14 posted 06-25-2019 03:00 PM

Miters in this application I would spline them and use an epoxy, polyurethane or other waterproof glue probably even construction adhesive would work.

You probably would be ok screwing them down, depends on how wide the boards are and how wet/dry the environment. On a porch exposed to the sun and maybe getting wet, allowing for movement is fairly important.

With this in mind I would consider something like foam packing between the post and boards.

Any reason for not using wood posts?

-- Everything is a prototype thats why its one of a kind!!

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therealSteveN

3116 posts in 996 days


#15 posted 06-25-2019 06:29 PM

Just using 2×2 spacers like those shown here will be adequate, provided they are spaced close enough together.

If you do go with the miter, then definitely spacers at the thick side, and if wider than 6” probably something more full length on the thinner mitered side. That mitered look is where the wheels will want to come off. clin wasn’t kidding, cedar likes to split, and it really likes to on the thin edges, like you get at the tip of a mitered cut. I don’t want the cedar I get to appear super human. If you leave it an option, it will split. I’ve had good success with it on full thicknesses. This is why I suggest you build the fake beams as shown on pic #2.

I don’t know all the places throughout Ohio, there are still Cols, Toledo, Cleveland, but I can say in Dayton and Cinci, only Requarth has what they have. In the past Paxtons in Cinci had some fair material, now they just have junk, and at really high prices. Requarth is a place best visited, I can’t walk through the lumber room without pointing ohhh ohhh how much is that. I probably drool more there than most places.

-- Think safe, be safe

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