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Mainebound
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# Posted: 22 Mar 2019 02:42
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I'm looking to purchase a small cabin and it's pretty new construction, looks great, but I noticed that the tie beams seem to have a little sag. Is this normal in a small cabin with a simple King post and logs for tie beams?
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Nobadays
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# Posted: 23 Mar 2019 13:52
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You didn't say how big these beams (logs?) are. Are they soft wood (pine, fir) or hardwood (oak, maple)? If they are 6"-8" it would take years for these to sag...even soft wood, but gravity will always win.
Is there sag in the beams or were they crooked to begin with and the builder didn't install them crown up?
I was waiting for someone else to answer but you deserve some kind of reply... I think others might want more info as well.
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ICC
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# Posted: 23 Mar 2019 14:33 - Edited by: ICC
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What does small mean? 12 to 16 feet?
No there really should not be noticable sag in the beams that span the width, not with properly installed king posts, assuming the rafters are also properly designed and installed. How about the roof ridge? Does the ridgeline sag or is it straight? If the ridgeline sags too, are the walls that the rafter ends rest on straight or are they bowed out?
FYI, maybe you know already, the king post is there to keep the beam from sagging. It works in tension, not in compression. Many believe the king post is supposed to prevent the ridge from sagging. Not so, the ridge should not sag because the rafters form a triangle along with the beam. Those triangles should not deform. The king post is actually hanging from the ridge and preventing the beam from sagging. At least that is what is behind the king post design.
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Mainebound
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# Posted: 23 Mar 2019 17:00 - Edited by: Mainebound
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The cabin is approximately 12'x35'. The ridgeline doesn't look like it's sagging. The tie beams are about 12'. I've uploaded some photos to hopefully show what I'm talking about. There's currently a couple feet of snow on the roof. I'm not sure what kind of wood it is. I viewed this property and couldn't actually get inside the day I was there. I'm still waiting on building permits to see if I can find out what it's built out of.
tiebeams1.jpg
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tiebeams2.jpg
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rockies
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# Posted: 23 Mar 2019 18:13 - Edited by: rockies
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Is the ridgeline sagging (you could see from outside if your roof dips in the middle). That beam and post design looks very DIY and I doubt it was engineered to support the roof. How are the beams attached to the walls?
I would change out those beams for three 2x12's and replace the little post too. At most the beams look like they are 6" round (and that's only at the widest point) so there isn't much material there providing support.
Do you have any idea what the ridge beam looks like? I doubt it's all one piece from one end of the cabin to the other so if the ridge beam is spliced in the middle then the beams and posts are really acting like more of a truss.
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toyota_mdt_tech
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# Posted: 23 Mar 2019 18:14 - Edited by: toyota_mdt_tech
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I'm thinking that is a ridge beam and not structured properly like rafters with rafter ties and trusses. And the ridge has sagged, transferring that to those logs. Are those hooked into a rafter or just secured to the top log?
I bet that is not structured right and the roof is sagging and could mean huge cost. A low cost fix may be a center support on the ridge and a jack to square up the ridge line again, run the load to a pier block under the cabin.
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Nobadays
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# Posted: 23 Mar 2019 19:10
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I put my money on Toyota's observations. Like icc said they shouldn't be sagging not as new as the construction looks...maybe not ever if correctly engineered.
Looks like some work to do there.... be prepared or walk away?
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ICC
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# Posted: 24 Mar 2019 11:33
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Wow, that is not what I would call "a little sag". That appears to be more serious. It was stated there is presently 2 feet of snow on the roof. I, personally would not make a decision to buy until the snow was gone and you can see what the ridgeline looks like. The way the 'king posts' are they appear to just be shoved in there and the sag makes it appear the ridge load is pushing down, which is bad construction.
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Brettny
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# Posted: 24 Mar 2019 11:51
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With a few feet of snow or any snow on the roof your not going to see much of a sag in the ridge line.
That bowing is bad. Very bad but can be fixe. That "king post" is almost doing nothins structurally. You dont need the vertical post of the horizontal ones can take the load pushing the walls out. If you can see that the horizontal beam has pulled away from the wall in anyway you will need to pull the walls back in. With the right tools and a good friend its fixable in a weekend. You may also benifit from adding a vertical support centraly to support the ridge beam better. Or just add more horizontal collar ties.
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NorthRick
Member
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# Posted: 24 Mar 2019 13:08
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If it were me, I would not buy that cabin. It clearly wasn't built properly.
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KinAlberta
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# Posted: 24 Mar 2019 13:24 - Edited by: KinAlberta
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Also note the cracking in the logs and in the first log what appears to be a notch of half the width of the log at the wall.
It also appears that the birch log might have been mitred into the midpoint thus reducing thd strength by reducing the effective depth.
No idea if this would suffice but:
Maybe just open the end walls to add vertical support then add a new deep ridge beam under the existing (assumed) ridge beam and then at say 12’ points down the length of thd room build up the strength of the cross beams. Fitch plates?
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Mainebound
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# Posted: 24 Mar 2019 14:44
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Thanks for all of the input everyone! You've all given us a ton to digest. Once I have a building plan and an inspector on site we'll make a decision on whether or not we want to fixer upper or bail.
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