Joist composition and deterioration - Woodworking Talk - Woodworkers Forum

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post #1 of 13 Old 01-08-2017, 03:43 PM Thread Starter
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Joist composition and deterioration

I have a house that is coming on 30 years old which I have been living in for around 25. Right after we moved in I put in a suspended ceiling that covered about 2/3 of the ceiling, and there were no problems. Recently, I started to put a ceiling in for some of the rest of the area and found what seemed like an odd situation. The joists are 8" and appear to be a yellow pine. When I drilled holes into the bottom of the bottom edge of the joist, I got a strange response from the drill. The wood would drill for about an inch and suddenly jump forward like I had hit an air space or layer of deteriorated wood, then I would hit another layer of wood, and an inch or less later hit another air space and clunk deeper into the wood without any drilling taking place. I have found this in the three or four joists that I have tried so far. I have never had any indication of insect damage, filings, or external exits and entrances that would indicate any kind of termite presence.

Can this type of wood some how dry out and shrink internally. Would this be and indication of any type of danger structurally?
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post #2 of 13 Old 01-08-2017, 03:52 PM
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that don't sound right to me ...

I would do a full inspection, from the top if possible and from the bottom, by removing the drywall from a large area, 2 ft square. What did the drill shavings look like? rotted wood, brown in color or still yellow? Do this now before it collapses.

You would also want to know if the supports are rafters or trusses...?
Is there living space above?

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo

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post #3 of 13 Old 01-08-2017, 03:53 PM
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What your describing sounds pretty typical for pine. The grain structure tender to have some pretty drastic variations in hardness, so the drill jumping like that is probably it just going through a harder part of the grain into a softer part.

Obviously if you think there's a problem it wouldn't be a bad idea to have a building inspector come out and take a look, but if there's no obvious signs of a problem, e.g visible rot, sagging in the joists, insect activity, I wouldn't be too inclined to stress over it

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post #4 of 13 Old 01-08-2017, 08:24 PM
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To me is sounds like the beam you see is hollow and there is a different member inside.
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post #5 of 13 Old 01-08-2017, 08:44 PM
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this happened to 4 joists

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Originally Posted by Steve Neul View Post
To me is sounds like the beam you see is hollow and there is a different member inside.
The Ops says it happened 4 times in different joists. Yellow Pine is a very solid wood in my experience, unlike White Pine. You just have to put eyes on this and determine what is going on..... that means removing some drywall.

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post #6 of 13 Old 01-09-2017, 01:29 AM Thread Starter
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This is a basement ceiling with a kitchen above, but most of joists are visible, and can be reached with no problem. I doubt there would be anything inside--it's just a plain old 2x8 piece of lumber. I said yellow pine but that was just a guess. I does not have any knots that I can see. The grain is around a quarter to half inch and runs fairly parallel. I suppose I could run a 1/2 to 3/4 of an inch in from the side and see if that shows me anything.
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post #7 of 13 Old 01-09-2017, 06:21 AM
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That sounds very typical of yellow pine. There's a very big difference in the annular rings. The early wood is very soft while the latewood is much, much harder. It sounds like you're drilling nearly perpendicular through the growth rings. As you hit the early wood, the drill flies through until it hits the latewood, which, being harder, takes a second or two to get through and then it jumps ahead again.

Should you be concerned? I wouldn't be. I'd take a look across the entire bottom of each joist and see if they're sagging in the middle at all. Some structures I've seen that are 25 years old were built overspanned and have sagging joists resulting from that but if you're not seeing any of that, rock and roll.
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post #8 of 13 Old 01-09-2017, 08:14 AM
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It has been a long time since I have seen the joists below the first floor of a house. However, 2x8 seems to me to be very small. What is the spacing and span on these?

George
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post #9 of 13 Old 01-09-2017, 11:21 AM
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Quote:
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It has been a long time since I have seen the joists below the first floor of a house. However, 2x8 seems to me to be very small. What is the spacing and span on these?

George
I agree. Having built more houses than I can count I don't think I saw anything smaller than 2x10 on 16" centers and most were 2x12.
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post #10 of 13 Old 01-09-2017, 12:04 PM
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You guys don't get around very much. I've seen quite a few floor joists done with 2x6's. This last summer I talked a customer out of buying a house when I found the floor joists were done with 2x4's.
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post #11 of 13 Old 01-09-2017, 01:32 PM
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Originally Posted by Steve Neul View Post
You guys don't get around very much. I've seen quite a few floor joists done with 2x6's. This last summer I talked a customer out of buying a house when I found the floor joists were done with 2x4's.
Most of the construction work I have done is in the northwest and I have never seen joists made of 2x6s or 2x4s, maybe 2x8s but I don't remember any.
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post #12 of 13 Old 01-10-2017, 05:39 PM Thread Starter
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2x8s on 16in centers. Spans from 8 in concrete foundation to a steel I-beam in the middle of the basement. Don't see any sagging, so I guess I'm OK.
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post #13 of 13 Old 01-10-2017, 06:47 PM
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Quote:
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2x8s on 16in centers. Spans from 8 in concrete foundation to a steel I-beam in the middle of the basement. Don't see any sagging, so I guess I'm OK.
If you think you have some deteriorating and weakening joist, you can just "sister" the joist by nailing or screwing a new 2 X 8" board to the joist that needs support. This is a fairly easy fix.
If you see no sagging or weakening from above, you're probably good to go.
You don't want to drill too many new holes in your joist of course.

If you don't have time to do it right the first time, when will you have time to do it over?
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