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  1. #1
    Join Date
    Mar 2007
    Location
    Western Montana
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    261

    Default Exterior graded T&G siding? or not

    The tongue & groove wood siding on this house seems to be pretty beat up for a 12 year old house (built in 2000). Lots of knot holes popping out. The prior owner has attempted to use clear caulk to seal some holes and small gaps between the lapboards.
    I doubt that this is cedar, looks like pine or fir to me, but I'm not a good judge of that. Looks like a low quality grade of wood.
    Real question is - are some T&G products rated for interior use only? If so, is there any way to tell? Do some wood siding products need to be painted instead of stained because they are a lower grade of wood?

    PS. There is no sheathing behind the siding at the gable walls in the attic. Pretty sure there is sheathing on the other walls (can see OSB at rim joists in the crawlspace). That is not part of the question, just an illustration of the type of decisions the builder made during construction.

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  2. #2
    Join Date
    Feb 2010
    Location
    Maine
    Posts
    14

    Default Re: Exterior graded T&G siding? or not

    I am not sure about the exterior graded question.

    To me the issue here is that with the many holes that appear from the knots falling out apparently and the caulking that has been done this siding is beyond its useful life.


  3. #3
    Join Date
    Mar 2007
    Location
    Western Montana
    Posts
    261

    Default Re: Exterior graded T&G siding? or not

    As to being end of life, the exterior siding should not be "end of life" at only 12 years old (and that is not a term that I throw around lightly). The picture I posted shows the worst example; other areas of the siding are weathered, but not full of empty knotholes. After all, you can always repair bad or damaged sections of siding.
    I would consider it "end of life" if it was:
    - very poor quality material to begin with,
    - had been improperly installed, or
    - was not rated for that use - therefore my question about whether there are some T&G wood products that are not rated for exterior use.

    Wood is graded by quality, number of knotholes, etc. For example, see Lap Siding Grades. But that is cedar, and I doubt this is cedar.

    Part of my confusion is that T&G wood planking is used for both interior paneling or ceiling material, or exterior use. I see several manufacturers and vendors when I do a internet search, but not any clear distinction between products designated for interior use only. Therefore, my question - are some T&G products rated for interior use only?


  4. #4
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,546

    Default Re: Exterior graded T&G siding? or not

    I can't be sure from the pics whether that is cedar or stained pine. The poorest grade of second growth cedar will have a lot of light colored sapwood sections, such as in your pics. The size of the knots and the way there are a lot of dry knots also suggests cedar, but it might be pine, or some species of interior fir.

    The wood may have come from a local mill, and it may never have been given a formal grade or inspection. The builder might remember where the wood came from.

    As a general rule, interior paneling would be sanded 1 side or both sides.That looks too rough for interior work, if you ask me. A fastidious builder would have trimmed off the worst knotholes. I'm not aware of a rule that says you have to use a higher grade for siding. The knot holes can be filled. For looks, stained knots looks better than painted knots, so I wouldn't go to paint just yet.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  5. #5
    Join Date
    Oct 2011
    Location
    Minneapolis, MN
    Posts
    780

    Default Re: Exterior graded T&G siding? or not

    How do you figure that's tongue and groove? Looks like 1X4 lapped planks to me - and barely lapped, at that. Better hope there aren't any holes in the housewrap, and that no one pokes through it where there's not sheathing. As far as I can tell, there are no set standards for interior/exterior siding. That definitely looks like a low grade of lumber, whatever it is...not something I'd put on my house!

    What did they use, finish nails?!

    Last edited by Kristi Silber; 05-07-2012 at 10:43 PM.
    Do not think of knocking out another person's brains because he differs in opinion from you. It would be as rational to knock yourself on the head because you differ from yourself ten years ago.
    - James Burgh, 1754.

  6. #6
    Join Date
    Apr 2011
    Location
    Bozeman, Montana
    Posts
    91

    Default Re: Exterior graded T&G siding? or not

    Terry,
    What's rated for exterior use, what can be used for exterior use, and what should be used for exterior use can be argued until the cows come home. My opinion is, this pine T&G was not a wise choice on this home, in this region, in this manner. High altitude sun, daily extreme temperature swings. Lap, shiplap, channel, dolly vardon are all acceptable profiles for this application even if the material is pine. The tongue on the product in your picture is more than likely about 3/8" long, which means each piece can only move a max of 3/16" before they let go of one and other. Also the the outside of the goove is only 1/4" at it's thickest (down to nothing at the bevel where the two meet), this isn't enough to hold the 2 together, over time when it rains and they suck up all that water because of the poor finish on this wall. Typically, in Montana T&G pine or cedar is used for exterior soffits or interior ceilings or wainscot. On the above mentioned siding profiles Knots are okay as long as they are tight. Stay away from quarter size and up in material that is 7/8's or less. The smaller the exposed surface area of an individual (across the grain) piece the better of course, but then up goes the labor cost. The biggest killer of a natural wood siding project is a bad paint or stain/sealer job. And your pictures show a poorly maintained wall.Using paint or stain, the pieces should be hit on all 6 surfaces before install. With stain, you should probably recoat every 3-4 years, and 2-3 on the sunny sides. Another killer of any siding project is improper nailing paterns or fasteners. It looks like they may have used staples in this one. Rambled on a bit, pardon me.


  7. #7
    Join Date
    Apr 2011
    Location
    Bozeman, Montana
    Posts
    91

    Default Re: Exterior graded T&G siding? or not

    Kristi,
    Take a look at a knot at the top edge of one of the pieces. There you can see the tongue. It appears as if it is 3/4x5 1/2 t&g bevel.


  8. #8
    Join Date
    Oct 2011
    Location
    Minneapolis, MN
    Posts
    780

    Default Re: Exterior graded T&G siding? or not

    I see a bevel now. Rabbeted I could see. Maybe it's the photos, but I still don't see tongue-and-groove. I'll take your word for it, though.

    Do not think of knocking out another person's brains because he differs in opinion from you. It would be as rational to knock yourself on the head because you differ from yourself ten years ago.
    - James Burgh, 1754.

  9. #9
    Join Date
    Mar 2007
    Location
    Western Montana
    Posts
    261

    Default Re: Exterior graded T&G siding? or not

    Thanks everyone. I agree that I wouldn't want that on my house either, but guess what - I have T1-11, but at least I know it is rated for exterior use. The exterior is definitely not smooth sanded, so the point about not being suitable for interior paneling makes sense. As far as holes, there is a very nice hole from a flicker (woodpecker) on the gable wall over the garage door, and not house wrap at all on the interior of that wall.

    Mark, good points about the length of the keys in the T&G and the weather exposure. I suspect that we have more swings of humidity levels in the Bitterroot than you have in Bozeman. Any comment about how you would write that up in an inspection report? I.E. just make observations and recommend review by siding contractor?


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