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Question DetailsAsked on 12/17/2014

Old house has cracks in floor joists and splits in main carrying beams. Do I need a engineer, inspector or what?

House is 140 years old.

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7 Answers

0
Votes

Wood beams naturally develop shrinkage cracks over time, but can also crack and fail if overloaded - and even if not overloaded, over long periods like you are talking about can creep and crackk and deflect substantially so they develop unacceptable sagging, even if structurally still safe.


Since you do not know if this is acceptable or dangerous cracking, a Structural Engineer is the one to best assess this situation.


If you want a thousand-mile opinion, you could post a few pictures here using the Answer This Question button right below your question, attaching photos using the leftmost yellow button right above the My Answer box. There are several building contractor and designer/ architect types who haunt this site that should be willing to give an opinion on whether what you are looking at is normal drying cracking, old age sagging, or something structural that needs immediate attention.

Answered 4 years ago by LCD

0
Votes

The proper remediation is likely to be simply adding a sister or double-sister to the beams that have the splits, and securing the sister(s) with Simpson strong-tie structural screws.


That aside, you will need either a professional engineer, structural engineer or architect (more expensive) to certify the appropriate remediation for your exact circumstance.


We had to do a bit of this after we gutted out our 1st floor - a few of the original 3x10 joists in the ceiling had some splitting. It's easy and inexpensive to add a few sisters.


Good luck!


J.

Answered 4 years ago by Jefferson

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Just in case you don't know what Jefferson meant by sistering - that is simple putting in a temporary prop to get the sagging old joist back up to where it should be, then putting a new joist (or structural plywood facing or steelplate) right next to the old one and nailed or bolted to it in a tight pattern so they act as one - that way the new joist or plate carries the load that the old one no longer can but the old one is still the nailing point for the flooring above. The problem with replacing joists entirely, which is the "cleaner" way, is you have to fully support all overlying load (usually by building a temporary stud wall with posts and beam andproviding jacks or blocking at the perimeter wall) while removing the old beam/joist, then you have to provide fastening of the subfloor to the new joist which is difficult to do with just nails or screws because you risk coming through the flooring above so it is commonly easier to just leave the old one in place and avoid the removal labor (assuming it is not rotted, which would spread to the new joist) and put a new one next to it or put reinforcing plates on it.


Both-side sistering or "twinning" involves placing a new joist or plate on both sides of the old one and bolting through all three so they act as one. Sometimes done when the floor loading above is high due to large bookcases or such or an overlying load-bearing wall (so you will have full new support of the plywood subfloor on both sides of the old joist or beam), and sometimes done with a "sister and baby" for that reason - a full new joist on one side for load capacity but just a 2x4 for subfloor nailing on the other side. Both-side sistering or twinning with full-size joist on each side is usually only done when the original (now damaged) joist was sized too small in the first place, or when the actual floor loading over it exceeds normal capacity for one joist, so you double up to provide a stronger beam to carry the increased load. This is also sometimes done when utilities have been run through the original joist in such a way as to unacceptably reduce its load capacity (like when an HVAC contractor runs amok with a sawzall and runs large ducting through the joists) so to avoid moving that utility run, doubled joists or double-face plywood or steel plate reinforcing are sometimes used to allow them to have the same cutout for the ducting butnow be able to bear the load.


Another common fix, especially in older houses where beams are cracking or excessively sagging but not totally failed, if acceptable from an aesthetic standpoint, is to add intermediate columns to cut the span in half, allowing the old beam to stay in use - sometimes with a bit of plywood or steel reinforcing plates in strategic locations, sometimes with nothing being done to the beam other than propping it back up to correct height with wood or pipe columns. In extreme cases, especially with crawlspaces or unfinished basements, if all the floor joists are in distress, a new beam crosswise to them the length of the house can be put in with newcolumn supports under it, if needed.


Determining which of these fixes is needed and most viable and what supports are needed under them and what fastener pattern is needed to make them act as one and be able to carry the load is where the structural engineer comes in.


In all these cases you commonly get into not only carpentry, but also utility issues because there is usually wiring and sometimes ducting and plumbing penetrating the original joist or running alongside it that has to be moved or disconnected and then reinstalled, so when that is the case you are usually into a General Contractor rather than just a Carpenter-Framing to do the work.


Structural Engineer is your best bet - because most architects arenot structural qualified and use a structural engineer (consultant or on-staff) for structural design anyway so you would be paying more than needed, and an inspector could tellyou that you need reinforcement or replacement but you would then still need the structural engineer to actually design the fix and provide the plans needed to get a building permit.

Answered 4 years ago by LCD

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Votes

Thanks for the suggestion to post a couple of pictures. Here are shots of a 8 x 8 beam that supports the floor joists.


In some parts of its length, there is a lengthwise split vertically up through the center.


In other parts, there's a lengthwise split running horizontally through the center.


Neither split is all the way through.

Answered 4 years ago by Guest_9324178

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You definitely need a structural engineer - and if you cannot get one in there in a few days, for peace of mind I would (DIY or Handyman) get a prop driven in under the left end of the first photo where the top half of the beam was cut through at the cross-beam or joist, causing the split - and at any other places where the beam has been deeply notched like that. If this is the case at every floor joist, I would put the below described support near the center (halfway between the end supports for the beam) then drive in 2x4 props under each other similar place to take up a bit of the load. I would normally have said use a 4x4, but because of the big longitudinal split in the beam I would say a pair of 4x4's side by side or a doubled up (and nailed together to make one post) pair of 2x8's to evenly support both sides of the middle split - either way toenailed or metal plated to the beam to be sure they cannot come loose or kick out.


Intent would not be to get the beam back up where it belongs at this point - just to take a bit of the load off it and prevent it from sagging more, because you have lost probably at least half of the load-carrying capacity of that beam so the only reason it is still there is because it had a healty safety factor in its design, but it is definitely on its last legs. So - it is clearly carrying the load right now, but probably marginally - so temporary support with cheap lumber just to keep it from deflecting and cracking more would be the immediate need - then it could sit like that for a bit while structural engineer comes up with a fix, and you get a contractor to do the repair. If a building department inspector saw it as it is now he would probably pull the occupancy certificate for the house and require it be vacated till propped up or fixed - I know I certainly would have.


The horizontal split is not good and should have been bolted together to stop the splitting once it started cracking, but does not dramatically affect the beam load carrying capacity - it is basically just like two beams half the width side by side. The horizontal split is the problem - your beam has essentially divided into two separate 4x8's laying on top of each other rather than an 8" deep beam. This takes away about half of its capacity to carry load between its supports, because doubling the beam depth increases its moment (bending) capacity by 4 fold, not 2 fold - hence, cutting depth in half cuts strength by 3/4, down to 1/4 the full-depth beam capacity. Two beams half the depth equals roughly 2 x 1/4 the strenght - about 1/2 the load bearing capacity in bending.


Looks like a DIY or barn builder home building job the way the beam and joists were handled - so I would expect to have to do replacement of the beam plus probably a few other mods - at least in how the joists are fastened to it, because unless that are grossly oversized for the load, they should be fastened to the beam over their entire height, not hanging down like that. There are a ton of different metal stiffener and splicing and joining connectors out there from Simpson and others to handle this sort of issue, so this is usually not a terribly hard thing to do - just will take some time because the floor joists are almost certainly going to have to be propped up by temporary stud supporting "walls" (bare studs) while the beam is replaced, because from what I see, unless you are prepared to lose a ton of headroom or put a continuous supporting wall or a whole series of supporting posts along underneath that beam, fixing it is probably a no-go.


Be sure when talking to the engineer that you make clear how important keeping the basement space open (wall-free) or post-free is to you, because with this old a house you probably don't want to spend a terrible amount of money fixing it up. It may well turn out that the most economic solution, and not an unusuall one in a very old house, will be an in-place fix without removing the beam or floor joists - putting in retrofit joist hangers (does not require removing joists), and beefing up the beam with a continuous wall or periodic posts under it to take most of the load off it, and maybe using steel plates and/or plywood overlays on the beam to strengthen it.

Answered 4 years ago by LCD

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Oops - my bad- reread this as a possible referral answer to another question, and noticed an error - I referenced the horizontal split twice, Should have read that the VERTICAL split in the second photo is not so serious, makes it equivalent to basically two half-width beams side by side - which should be fixed or replaced, but not probably an imminent hazard. The HORIZONTAL split in the first photo is not good at all.


Clearly this was a DIY or barn-builder job, because the way the beams are cut halfway through like lincoln logs is NOT the right way to do beams without direct post support under the intersections- and not at all if that depth beam is really needed to carry the load. I suspect after an engineer looks at it, the recommendation will be (assuming you do not want to entirely reframe the beams) will be adding support posts several places, and bolting together or plywood or steel cover-plating or using supporting brackets at some of the cracked sections.

Answered 4 years ago by LCD

0
Votes


Hi,


I saw some other pictures posted here so thought I would give it a shot. These are pictures of a wooden support beam in the basement. I am wondering if these cracks are an issue and if I need an inspector or structural engineer?


Thanks!

Source: Matt

Answered 3 years ago by MattS




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