Exposed untreated pine shiplap siding / Pine tar
Can I leave the back side of pine shiplap siding permanently untreated ? And the front side untreated for 12 + weeks ?
I’m getting close to installing pine tar coated vertical pine 1 x 8 shiplap rough side out here in CZ5. It will be installed on 1 x4 double strapped furring on 3″ rigid mineral wool. Two story with minimal eave overhang. I want to get the siding up asap for obvious reasons.
However, the pine tar application is being done by me (part time) and it will take a long time (10 minutes per board x 600 = 100 hours). Drying could take a couple of weeks.
One potential option I thought of is to install the siding totally untreated and then apply the pine tar to the face in the Spring. This would leave the back side of the siding left permanently untreated and the front side left untreated/exposed for 12+ weeks.
Is this a bad idea ? Or will the siding be just fine for 20 years ? The pine tar dealer says it’s okay to leave the back side untreated. The pine tar mixture is currently 50% pine tar and 50% raw linseed oil. From what I understand, I could add gum turpentine which will allow a deeper penetration and faster drying time. The rough side really soaks things up though.
Here’s a photo of a board with one coat (not yet dry). It’s really beautiful imo.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
We are well past peak black, I would be careful with too much of it on the house.
My suggestion would be to take 10% to 15% of the shiplap and coat it black for a couple of accents. Anything that will be black needs to be coated before installed otherwise as the wood shrink and expands it will expose unfinished sections at the overlap which is a very noticeable eyesore.
The rest I would leave bare wood and let it age.
Generally pine over a rain screen holds up very well, you can compare the conditions to the siding on an old barn. It will grey and weather over time but it will last. A coat of water borne wood sealer won't hurt. This can go on after all the boards are up, keep in mind lot of the wood sealers won't allow future paint/stain to stick.
Akos - I hear you about peak black. My wife (interior designer) won't be swayed (I tried presenting other options) - though I still love the rough sawn/ pine tar look and feel. We are on a few heavily wooded acres, dirt road, rural with an eclectic assortment of home styles (and numerous barns). The mass / form of our structure is similar to a Kentucky tobacco barn ( with a modern interior). Though black has peaked (which I'm grateful for), I feel it's here to stay. In any case, when we become empty nesters in 10-12 years, and if we decide to sell, I'm sure there will still be plenty of NYC folk (one hour away) who will re-clad if so desired.
Yes, the gaps ! Definitely was a concern of mine. If I install now with dry wood/ low humidity, how do you think will this affect the gapping long term ? Will there be gaps eventually ? Will the gaps get larger over the course, of say, five years ? The rough face really soaks up the pine tar. If I had to go back and fill the gaps, I don't think the appearance of the face wood be affected.
I appreciate your input Akos.
Doesn't matter how dry the wood, the house and structure bellow will move, eventually you'll get gaps. With a dark color, I would not take a chance.
Got it. Makes sense. Thank you Akos
I don't have an exact answer for your question but I do have some experiences with pine tar. I did a small project this summer with a few band sawn pine boards as accent trim around a new front door. I used Auson black pine tar and the dealer recommended mixing with purified linseed oil only to speed up drying. I finished both sides and found in direct sunlight the boards dried in less than 2 days. If you don't want to apply the pine tar to the backside it might not be a bad idea to apply a quick coat of straight purified linseed only to provide some protection.
db,
That looks great ! Thanks for the recommendation. My mixture is 50/50 with raw linseed oil. I might have gotten it wrong, but I thought I had read that the linseed oil prolonged drying time. I'll double check on that for sure. I did hear that gum turpentine (and penetration) will speed up drying time. I do wish i could do all of this outdoors, including the drying, but with the cold climate everything is being done indoors. I'm grateful that i'm pretty much dried in/ sealed up and I can get my temp electric heaters to maintain a min of 60 degrees at an outdoor of 30. I can get 70 degrees no problem right now with this crazy warm february. Thank you for the response.
Thanks,
I'm pretty sure the linseed oil dilution is primarily to reduce the viscosity of the pine tar. Allowing it to penetrate the wood more effectively as well. Even in warm temps it took a minute or 2 of a drill paddle to mix well. You can also heat the pine tar on a hot plate or similar to make it more flowable in colder temps. Also, having used raw and purified linseed oil in many other woodworking projects the purified oil certainly dries faster, but not as quick as BLO.
Appreciate the additional info. I have premixed - 50/50 pine tar & purified LO. I'm going to look further into turpentine as a drying agent. I read somewhere that 1/3 of each will provide better drying and penetration. My first test batch of siding is 90 % dry at one week. The smooth sides are taking longer. And yes, ty, I have two crockpots
"However, the pine tar application is being done by me (part time) and it will take a long time (10 minutes per board x 600 = 100 hours). Drying could take a couple of weeks."
You would be time ahead to coat both sides by making a dunking tank or spray center and batching that up. You can't spend 100 hours applying paint, you've got other things to do!
However, I think I agree with Akos here. Solid black was a short lived fad. Lasting for eternity may not be a feature on the whole house.
Kyle,
Dunking sounds fascinating and this could be a game changer. I'm curious about he penetration rate/time. Does it need to soak for a specific time ? Still, sounds like a lot less effort. If I can cut it down to 2 minutes per board, then I can do two batches over two days and then allow for up to two weeks drying and be ready to go.
Thanks for the input !
We used a trough for dunking our siding using tung oil, which sped things up as Kyle points out.
The tung oil didn't hold up well, so we switched to the Auson black pine tar a couple of years after the initial installation --- it's holding up much better.
You'll still need to squeegee/brush off the excess, but it's definitely more fun than rolling/brushing out each board by hand.
Black siding makes a strong statement, so it's not to everyone's taste. I'm still glad we went with mostly black on our house.
Nice trough! Do you mind sharing any tips to prevent the oil from leaking?
Adam
I just used a high quality latex caulk/sealant to fill all the gaps and seams.
Hi Eric,
First off, I want to let you know that I read and re-read many of your posts which were invaluable in gaining knowledge on PGH practices and techniques, particularly the exterior posts (I think it was a two part post). Excellent. Thank you.
You were exactly right about the challenges of finding good contractors willing to take on these kinds of projects with th learning and details that it requires. Like exterior mineral wool. With gaining the knowledge (on paper, so to speak), transferring that knowledge to my carpenters, being there with them at every step, etc, it was a total success.
If you had previously posted about your trough, I missed it. Great setup. I will seriously consider this. A squeegee sounds interesting. How did you get the excess off of the laps ? Even then, did you have dripping to the lower tiers of the drying rack ?
Indeed, black siding is a bold statement. Glad to hear you're satisfied with your decision. I'm pretty certain I will be as well.
Thanks for the kind words! It's always nice to hear from people who have found the info on our blog helpful. Glad to hear that your project is going well.
There's more info and pics about the trough here:
https://kimchiandkraut.net/2016/12/05/oiling-charred-cedar-siding/
You'll see we used blocks of 2x4 to create a small ledge inside the trough. Resting a board on the ledge meant any excess pulled off by the squeegee ended up back inside the trough (reducing waste).
At that point, the board got moved to some sawhorses where we used a brush to further wipe off any excess, and hopefully get a little more penetration into the wood.
I never used the black pine tar with the trough, so you may want to set up a small version first just to make sure it'll work for you.
Thanks again Eric. I'll let you know if I decide to set a trough up.
While pine boards over a rain screen usually hold up pretty well, one of the main reasons you should coat all sides of any wood used on the exterior is that coatings slow moisture absorption. If you have damp air in the rain screen gap the boards will readily absorb it and swell, but the face with a coating will be drier, resulting in boards that cup. I've seen pine boards and cedar clapboards cupped so badly they popped off the wall. I recommend fully coating any exterior wood that has a coating that slows moisture movement. Or leave it fully unfinished.
I'll take your advice. I'm too invested in the pine tar strategy, so looks like i'll be hunkering down, brush or trough. I've gained a lot of knowledge in reading your articles / watching your videos, particularly your slabless slab design. Really great work. TY
Thanks, I'm glad you have found my writing to be helpful!
To save some money and mess on finishes you could probably use regular boiled linseed oil on the back of your boards. Do you have a finish sprayer? You can get a good airless sprayer for under $1K that would speed things up, though it also goes through more material and makes a mess. But if time is short, it's what I would do, though I already have the sprayer.
No. I don’t have a sprayer. Though I’m doing this indoors in order to control temperature. I think I can get this down to three weeks with a couple of helpers and adding 1/3 gum turpentine (to speed drying)
I really like the look of the rough sawn pine. With the pine tar, it seems to mimic the charred wood look. Here’s an update picture. I was originally proposing cedar, but it was about $20k more.
It looks great! I'm planning an addition at my house and will consider that for a finish. Thanks for sharing.
Looks great! Can you verify what species of board you used and the ratio of tar/oil/turp? Did you end up rolling it and did it take more than one application?
Hi clads,
I used eastern white pine, 6" shiplap, rough on one side. I have the rough facing out. The ratio was 50% pine tar and 50% raw linseed oil. Brushing it on ended up being the most efficient way for me, though on Eric, in a post above, used a trough system and dunked them. I warmed the pine tar in slow cookers. One coat was sufficient for the rough side. the smooth side could have used two coats if I was going to have them faced out. I am waiting a year or two and might add another coat. Attached is a picture to give you an idea of how it came out
Looks great! Very encouraging to see, we are planning something very similar.
Thank you. good luck with your project !
Thanks for the quick feedback! I like the trough system. Based on your experience brushing it on, do you think the boards would need to be brushed after dunking? if so, it would seem to reduce the benefit of dunking.
I think you probably need to do some brushing for excess. If you are going to have the smooth side facing out, I'm not sure if the dunking will get proper penetration or not. I think it would for the rough side. You could do a test run with some small pieces/ small dunking container. The biggest hassle for me was that a lot of this was done when it was cold out (and I didn't have a fully heated space). It took a couple of weeks to dry. Some of it was done when it was warmer and it dried in about 5 days.