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-   -   Cracked Basement Beam (http://www.diychatroom.com/f19/cracked-basement-beam-7701/)

lpcon 04-10-2007 10:34 PM

Cracked Basement Beam
 
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I am in the process of redoing my basement and have hired a contractor to lower the basement floor and do the necessary underpinning. During the renovations it became obvious that the previous owner had removed one of columns supporting the beam running the length of the house (the beam is 27ft long and was only supported 9ft from one end). Two steel columns have now be installed at 9ft centers. The engineer originally thought that this beam was made up of 4 - 2 x 10's - in fact the beam is 4 - 2 x 8's and has now said that a LVL beam will have to be bolted to the existing beam to give it the necessary strength

Getting to the point; I see a diagonal crack in one of the 2 x 8's , the crack is about 4 ft long and right in between the back wall and the first steel column. Do I cut out this damaged 2 x 8 and replace it? If so how long of a piece should be removed - just the cracked section or a 9ft section (ie from the wall to the first column)? At present only 3 of the 4 - 2 x 8's are supported into the back wall; the 4th 2 x 8 (the cracked one) only butts up to the wall.

Any input would be appreciated.

handy man88 04-11-2007 06:32 AM

Here's what I would do:

1) Clean out the crack.

2) Apply construction adhesive inside the crack.

3) Jack the beam up to close the crack with a temporary brace.

4) Drive lag bolts up the underside to secure the crack. Make sure you predrill.

5) Apply construction adhesive to 2 pieces of 2x8 that overlap the length of the cracked area, and sister the beam on each side (if accessible) of the cracked area with nails.

5a) If you want extra support, I would bolt the sisters in place instead of just nailing.

6) Allow ample time for the adhesive to cure before removing temporary brace.

AtlanticWBConst. 04-11-2007 06:39 AM

Quote:

Originally Posted by lpcon (Post 40454)
.... The engineer originally thought that this beam was made up of 4 - 2 x 10's - in fact the beam is 4 - 2 x 8's and has now said that a LVL beam will have to be bolted to the existing beam to give it the necessary strength.... Getting to the point; I see a diagonal crack in one of the 2 x 8's....

Why don't you get back in touch with the engineer and talk to him about all of this, and get his input based on the load calculations that he must already have from you....

Ron6519 04-11-2007 07:44 AM

Ipcon said:
"At present only 3 of the 4 - 2 x 8's are supported into the back wall; the 4th 2 x 8 (the cracked one) only butts up to the wall."

The cracked beam wasn't there originally. It was added on at one point in some attempt to probably compensate for the removed posts.
Agree with Atlantic, speak to the engineer.
Ron

lpcon 04-11-2007 11:36 AM

Thanks for the input. I have already contacted the engineer and should get feedback from her later this week. I like the repair procedure posted by handy man88 - it makes sense to me.

Another question:
At present three of the four 2 x 8's are "pocketed" into the block wall. Do I need to install a bracket to "connect" the 4th 2 x 8 to the wall? When installing the additional LVL beam would it be required to install a bracket so that it is also connected to the wall or is it sufficient to just have it bolted to the existing beam?

Thanks

handy man88 04-11-2007 12:59 PM

When you sister the broken beam, the extended length of the sisters could be placed on top of the block wall, if space allows. If not, you may want to put a permanent post against the wall to hold up the 4th beam.

How is the floor directly above these 4 beams? Your unsupported 4th beam has done nothing for you this long, so if there's no sag, then removing the 4th beam altogether may be a good idea especially since you're installing a LVL also.

AtlanticWBConst. 04-11-2007 03:48 PM

Quote:

Originally Posted by lpcon (Post 40520)
Another question:
At present three of the four 2 x 8's are "pocketed" into the block wall. Do I need to install a bracket to "connect" the 4th 2 x 8 to the wall? When installing the additional LVL beam would it be required to install a bracket so that it is also connected to the wall or is it sufficient to just have it bolted to the existing beam?
Thanks

Hi Ipcon,

These, actually, are all questions that your engineer can help you out with....You should speak to her about this.

handy man88 04-11-2007 06:44 PM

You have really two options. Either have the 2x8 & LVL pocketed also into the block wall, or have a dedicated steel post supporting the beams. Using both is the best structural option.

Having a beam pocketed distributes the compressive load (weight) of the house onto the beam and then onto the wall or post, which is what it's designed to support. If you use brackets/bolts, the compressive load is translated into a shearing force onto the bolts/bracket. The bolts/bracket may or may not hold up, but the cement blocks could/would crumble over time.

You should never sister the LVL onto the existing beams because it wouldn't be doing anything but be attached to the beams. Beams are ideally simply supported on both ends. In order for the LVL and 2x8 beam to work, you would need to jack the basement ceiling up, insert the LVL and 2x8 beam, and then lower the floor onto the LVL and 2x8 beam.

lpcon 04-11-2007 09:04 PM

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AtlanticWBConst.: you are correct in saying that the engineer can give input on this, however she was the one who got the beam size incorrect. So I will still take her input, but I also want get input so that this problem is fixed correctly.

handy man88: Prior to the 2nd post being installed the beam had definitely sagged and this can be seen in the drywall on the ground floor. In the center of the house the drywall has rippled in some areas - compressive stresses and at the back of the house (above area where beam has split) cracks are visible - the cracks are not wide spread but definitely noticeable! I also believe that the beam was not adequately supported while replacement post was being installed - the jacking post was placed on sand right next to a pit so soil was giving way and the jacking post felt loose.

In your last post you definitely focused on concerns I had ie how do you support the new beams and how do you ensure that it takes the load it needs to. I double checked and the cracked 2 x 8 is not attached to either the south or north wall. So if I understand it correctly the only way to create adequate support is to pocket the lvl into both the north and south wall. I am thinking it should still be bolted to the existing 2 x 8's to create a solid block? A pocket can be created on the north wall but the south wall is a different story (see picture). The beam is right next to the chimney connection for the water heater and furnace. The other option is to install a post but I am concerned about opening up around the footing for the pad for such a post. Would it be reasonable to bolt a steel or wood beam along the back wall to support the lvl? At least this way the load would be tranferred along the entire height of the wall and accross say 10 anchor bolts?

Once again thanks for both or your inputs!

joasis 04-11-2007 09:10 PM

I will add another option not discussed, but if I were on this one, and absolutely did not want to pull the existing beam, I would strongly consider using lengths of 8 inch channel iron bolted through the beam midway between the lally collumns and again at the collumn. That would be sucurity for a lifetime. You could also "fishplate" the beam with 1/4 inch plate sheared 7 inches wide by 12 feet long, in effect, "sistering" the beam with steel, and through bolting as above with 1/2 inch bolts. Both of these fixes will excede what your engineer wants, and permanently solve the problem....maybe even cheaper then the lvl.

handy man88 04-11-2007 10:09 PM

I would discourage against bolting a steel or wood beam along the back wall like a deck ledger board to support the lvl. First off, your wall is not a poured foundation, but cinderblock, so you have to consider that it's not that strong to begin with. Once you bolt a beam along the wall to support the lvl, you're in fact introducing a bending moment on the wall, as opposed to a strictly compressive load on the wall. The hollow cinderblock could crumble at the bolt areas. Cinderblocks are hollow, and are only about 1 inch thick, not much meat for the bolts to sink in to.

Using a post is a much better idea, but the question is how you will support the single LVL on the post. Usually, steel ibeams sit on top of the posts where the interface is welded. LVL's and floor joists then sit on top of the ibeam and the concrete foundation. Pockets are are created for the ibeams into the concrete foundation.

Since there was so much sagging based on a poor support, you have to wonder if the integrity of the existing beams have been compromised. If you jack the floor up, you might see a huge bow in the beams. In a perfect world, I would remove everything there right now and install a steel ibeam in its place. Or, install a double LVL. Bolting onto the existing beams is not an issue. Just make sure all beams are contacting the ceiling and doing their jobs.

Also, the idea of bolting on a plate to "sister" the existing beams is not a bad idea. The only thing is the plate serves as to reinforce the existing wood beams, as opposed to holding up the ceiling. The beams could still crumble, as you now have the extra weight of the steel plates putting stress on the beams that you just drilled holes into in order to bolt.

joasis 04-12-2007 05:58 AM

If you read my post, you would see I was suggesting only a repair to the existing beam. Unless there is water present, or a major termite problem, the idea of the beam "crumbling" because of steel plates bolted to it is ludicrous. If there is a water problem, then new beams, LVL's, or sistering a load bearing beam with 2x8's is not a fix.

Rather then create a ledger, you can add an end collumn and secure it to the wall.

You will catch a ton of advice on loads and distribution of loading on structures, but remember why you had an engineer in there in the first place. Also, houses do not weight as much as some people would have you believe....so consider the loads you are supporting in real terms.....and do not rely on advice from this forum to replace a qualified opinion that is on your site.

handy man88 04-12-2007 07:47 AM

FYI, I'm a qualified engineer, but building laws vary from state to state.


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