This may be slightly off topic, but because it is in my trainroom I feel that it qualifies. Here’s the situation:
Five years ago I played general contractor and built the house that I live in. For the most part I am very happy with the results. There are a few minor problems, but none too serious. What I am about to describe is by far the worst, and slightly worrysome.
The house is 40 feet wide, as such there needed to be some center support for the main floor. The roof places no load on the floor, as it is supported entirely by the outside walls.
If you look closely you can see 3 support columns which hold up 2 microlam beams. The problem is with the one closest to the camera.
When the time came to install the beams, we discovered that they were not exactly the same height. Furthermore, the support columns were about an inch too tall, even at their shortest adjustment. It was decided to slightly notch the beams, and solve both problems at once, rather than incur any delay. The carpenters inserted some shims, which they felt were necessary at the time. Keep in mind that there was no load to speak of at the time of construction.
Now 5 years later, with the house fully loaded, the situation has changed. The column is no longer plumb. It has migrated 1/2 an inch. My theory is that the shims are mostly to blame.
Here are some closeups of the actual situation.
The photo above shows the problem most clearly. If left unchecked, I am worried that eventually the column will migrate to the point of catastrophic failure.
In this photo you can see that the lag bolts used to secure the beams to the top of the column are beginning to spl
First to avoid liability, I’m not a structural enginner. I’ve come across siimilar situations as a facility engineer during my past life. You are correct in assuming this a potential failure.
Your plan of taking the weight off of the column is correct, the beam should not have been notched, the affective area is only that left at the smallest dimension, height, with the notch corners further aggrivating shear stresses.
I’d suggest taking the weight off the column, installing steel splice plates, through bolted, to both sides of the beam, replumbing and adjusting the height of the column, checking the beam for level, and securing it at the base with a min. of concrete anchors
If you don’t have a sufficeint footing under the column now would be the time to install one.
Elliot, a big email has been sent to you. I see in the sketch that your house is six years old which I didn’t see before I sent the email.
The notch at the end does not concern me, (but I will need a measurement) because the controlling factor in the design of a beam with a non-variable moment of inertia is the moment at the center of the simple span. If the span length was shorter, say 6-8 feet, then shear could be the controlling factor. (Bar joists used above commercial building hallways are often a much smaller depth because shear governs the design, not moment.)
However, wood is generally strong in tension and compression parallel to the grain and weak when stressed perpendicular to the grain. Wood is weak in shear because it has a tendency to split along the natural grain laminations. Glue lam beam manufacturers realize this and the factors of safety are much higher. Wood has a tension strength somewhere between 6KSI and 8KSI, and a compressive strength of 3KSI and 5KSI (Steel is at 24KSI to 60KSI or higher for specialty steels.)
Another thing to you could do after taking the weight off and removing the old post is to mortat cinder blocks and lay them up to the beam then secure a metal plate at the top to fit the beam into. Cement that mmetal ear plate into the top of the blocks, then bolt beam. This should give it stability and hold the weight.
laz 57
Great suggestion, but we need to find out the cause of the movement so that this solution will not have a problem in the future. If Big Boy lived in West Virginia or Pennsylvania, we could almost assume that the soil is moving the house down the hill, but I believe he lives in a highly glaciated area of the county with well drained soils.
Disclaimer: I am not trained as a structural engineer. I am not a registered professional engineer.
It looks to me from Elliot’s diagram that the beams may simply have warped. It makes me suspicious that there are HVAC ducts on either side. Could one of them have a leak that has induced the beams to twist?
Roger, the bottom of the column is very secure as it was properly bolted to the slab. Each of the columns has a precast concrete pad under the slab to handel the point loading. The idea of a steel splice plate has crossed my mind, though it would be difficult to install because of the duct work.
Buck, I got your email and I will call you. The house is not traditional construction. All of the exterior walls, both foundation and main floor, are precast concrete panels. They are bolted and glued together with their joints staggered. There is no indication of cracking or movemnt at the perimeter. This problem has been more of a slow creep over time, not one sudden motion. The house is very large, and preforms well in wind, though thunder causes the entire house to act like a drum.
I have reason to believe that the shims have predisposed this column to want to kick out. By removing them and resecuring everything, and bracing the beam into a straight position. There are very few fasteners involved with this beam system. Gravity is the main one. This column supports roughly 240 square feet of the main floor, most of which has nothing on it.
Thanks Bob, but everything is high and dry here, perhaps too dry. The ducts are hung from the floor joists, and there has been no dripping anywhere in the house. I’ll have to call my HVAC guy, and see if he remembers how severe the warp was when he installed the ducts. I seem to recall that he mentioned that the beam was crooked back when the house was still under construction. There is some warping in one of the microlams. The two sistered beams are only held together with nails, this may be a contributing factor in allowing things to migrate.
I follow you BUCKEYE but maybe and I’m just throwing this out, check the foundations of the piers for they needed a footer under every pier. Or like you said it could be the shift in plates.
laz57
Houses frequently “settle” just a bit the first year, but shouldn’t be moving like that. That’s way too much. Sometimes the builders don’t do too good of a job tamping the dirt before pouring the slab and sides. Our neighborhood was built on fill and poor tamping resulted in sink holes sprouting up.
Rabbits have taken residence in some of these holes, much to the deliight of BB the beagle.
I would only add that you may wi***o expand the side plates concept a bit and actually make the plates into a saddle that wraps the beam’s joint from underneath and to each side. This would provide an additional bearing plate for the column and contain the lateral (sideways) spliting/deflection the one beam is experiencing at the joint (It appears to me that you have a bit of failure in one of the laminated beams from your photos - see the next to last photo - beam on the left).
One other caution. It is likely the locations of the posts have a footing for weight distribution. The rest of your slab will not. Make sure when you install the jacks that you add load distribution footings with several layers of plywood (ie 2’x2’ foot) or timbers (like cribbing). A 10 ton jack with a small floor footprint could exert a lot of pressure on a small area of the concrete slab, causing spalling or worse a crack.
Also when you jack the floor, move it no more than about 1/4 inch per day to avoid stress in the structure (which has taken a “set”). Wood gets more brittle with time (and particularly a dry environment).
BTW - another thought would be to add some bracing to each side of the beam to prevent it deflecting. You need to make sure it is realigned to be perfectly vertical when you do the repair as it will not handle load well being off-vertical.
I was thinking not of liquid water but more of hot or cold air whose humidity or lack of it might have created an asymmetrical moisture content in the beams. Weyerhauser says that “Microllam® LVL offers consistent moisture content, resists warping, splitting and shrinking…” So the fact that the beams did warp may mean that moisture is getting into or being drawn out of one side.
I am just a retired Corps of Engineers physycist and have not had formal general engineering training, but my mechanics courses knowledge has raised several red flags here.
First, the beams should not have been notched. I would have trimmed the height of the support columns to fit.
Second, the notches should not have been cut with right angles at the corners. This causes stresses to be concentrated at the corner. A 45 or 60 degree angle would have been much safer.
Third, those lag bolts are entirely too near the edges of the beams. I feel there should be at least 1/3 of the beam material outside the bolts. Any side thrust cannot be resisted by the wood since there is not enough of it outside of the lag bolts. Two lag bolts on the center line of the beams would do more than the four now in place.
My fix, for what it’s worth, would be to construct a “U” shaped saddle at least 2 feet long that would be thru-bolted with 1/2" bolts to squeeze the beams and resist the tendency to warp. The top plate of the column appears to be wider than the beam. I would consider tack welding the in-line portion of the column to the beam saddle. If shifting does continue the welds would have a tendency to crack, alerting you to the problem.
OK ll you real experts! I have demonstrated my profound ignorance here and I really would appreciate a critique. [B)]
It sounds just like the repairs I had done to my last house. Although we don’t have basements here in California, there is a crawlspace under most houses, and they use a pier and beam system to support the floors. While in the process of selling the house, the building inspector discovered that a few of the support posts were leaning and needed repair/replacement. So, two guys with heavy duty jacks crawled around under the house and fixed the posts. Of course, there was no mystery as to how they got that way in the land of earthquakes. They did install U shaped brackets that have been mentioned in other posts for added stability. Good luck, Elliot.
Hello Elliot : I have been in Electrical contracting for 30 years, I AM NOT an Engineer, You have had a lot of EXCELLENT input so far. What I do know is this, The lag bolts should never have been installed that way & the Microlam should never be notched, cut or drilled or have anything fastened to it ( That’s the way it is up here). Last, where was the local building inspection when it was installed ? I hope you get things resolved soon in a proper manner. Kind regards Steve
Well guys, I just got off the phone with Buckeye Riveter, and after giving him all the details, he seems to think that my plan has merit. The problem is ugly looking but not that severe. It is clearly confined to the one post of the three, and should be fairly easy to correct.
As for the notches in the beams, they may not be the best practice, but they do not compromise the structure. The load bearing capacity of the remaining material, far exceedes the load applied.
The theory as to the cause of the problem is pointing toward the idea that the beams were not properly fastened together or secured to the top of the column. This combined with the repeated pounding of the floor, above the already unstable post, is the most likely cause.
I want to thank everyone for their input and well wishes. I will keep you “POSTED” on my progress.[swg]
Your more than welcome Big Boy. It was good talking with you today and I hope thirty years of structural engineering has helped you. I was certainly glad to learn that your joists were tonailed to the beam. This means that the beam’s top flange is restricted from rotational displacement.
And for those of you that really want to know why the notches do not compromise the structural integretity of the beams, just send me a big check and I will send you the calculations or go look at any steel joist roof system paying particular attention to the bearings at the end of the members. (Now you are going to wonder why they are so tiny and the joists so deep.)
I’m trying to figure out why Big Boy posted this in the first place.
A private message to Buckeye would have been good enough.
My first call would be to my insurance agent!
( Because, It does not matter who’s advice you follow OR how good of a job you do,
You are still liable should anything go wrong.)
The next call would be to the local inspector!
(To get a first hand account of the situation and to know my local code!)
My next move would be to find info by posting to sites dealing in this matter and sending a PM to Buckeye.
After all that I might consider posting it on this forum to share this situation.
What ever you do Elliot, Please follow your local building codes!
Seriously no joke I’m a licensed Professional engineer and structural engineer.
I’m also an attorney dealing in construction law. I have local counsels in all states.
