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Cracked floor joist in basement- repair

EddieBuskeddy's picture

I am a newbie here with posting so bear with me. I have an old craftsman era 1924 with charm but old bones. I am homeowner without building experience. I am meeting with hardwood floor man today but really interested in underneath to start and assume he will have opinions. I will take bids but want ideas and may share some here shortly.

The there are two timbers with significant cracks (out of a knot) and some slight sag. This is followed by a good timber then one more impacted by clean air duct "alteration" work, where they cut a joist and blocked to the apposing joists one either side. (Each of those two joists looks good).

I am thinking that each of the joists needs to be married with new Timber and bolted. I will not do the work but will want it done right... Any thoughts on shoring up the old bones? How do you get weight to transfer correctly? How much correction can be made in sag before upstairs floor starts to shift? My floor guy will have strong opinions here I assume.

Respectfully submitted.

(post #80840, reply #1 of 4)

First off, don't discount the simple fix of just propping up the failing joists, if the associated posts (lally columns) won't be in the way. It's not in any way an inferior approach, other than the obstruction created by the posts.

Second, what you're presumably talking about is "sistering" the joists (joining new wood piece to old to reenforce the old). Always good to know the right terms when talking to a tradesman.

How big are the joists? Measure thickness and height (to within a quarter inch or so) and post here. Length (between supports) within a foot or so would also be helpful.

If your view never changes you're following the wrong leader

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(post #80840, reply #2 of 4)

Welcome to breaktime ed.

You should go down there with a tape and if possible, a digital camera.  Measure the size of joists, the span and the centers.  Take a few pics of the underside, specifically your areas of concern.  Also include the loads from above that might fall on that floor system.

Post the pictures here along with the information and we might be able to offer suggestions on what to do to shore it up properly.

Your floor guy should be a help if he has any experience in framing.

Best of luck.

photo should be jpegs and about 75 kb's.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


(post #80840, reply #3 of 4)

The section of concern is rectangular space with joist running about 10'3'' (width) from edge of sill to edge of beam near center of basement.   (I did not measure length but beam runs down center of house which is about 15,000 square ft.- not including basement).   The joists are 2X8 and 16' on center as typical.      There was some repair prior to my purchase of home (replaced 3 posts under beam).  As I write this, I'm thinking (gee) look up who did that and discuss the work they did to determine if slight shift impacted the joists and if they are willing or accountable to respond and review... (assuming professional- and part of record and hopefully an existing outfit).

The two cracked joists are next to each other and the cracks are in roughly in line about 3 feet from the beam.   Directly above the beam is upstairs wall and above the cracks a hallway.  The floor of the halfway is uneven (bows out some) and there is old repair of wood floor.   There is one more floor above.   All the floors are a bit spongy but flat- not including that area discussed, and top floor with a bit of a slope/drop from center of house (two stories above and about three feet on opposite side of beam basement).        There is newish floor up there which is smoothly laid over that slight slope.   I may get some pictures if I can figure this posting stuff out (newbie here).  My floor guy showed up and is recommending that he "sister" new 2X8 to the old timbers and states he's done this before (hx of framing).   He will also pull a line to check bow and use some pole lifts to move joist up about 16th of inch up around crack before sistering with lag bolts.   I may consider new post but worry it will look odd/raise question about stability....on resale.... (want to do it right and safe though and will see).

Any thoughts or web resources I could print off for his review?  I will get one or two more bid before moving next week on project.... plumber needs to undue/redue some work there too....

Thank you in advance for any input.


(post #80840, reply #4 of 4)

Ed,  first off I'm not real good at following descriptions-there's alot more folks here that do a much better job understanding.

The sistering of sagging joists can be done a couple different ways.  Glue/ nail where the use of glue is often questioned as a benefit, through bolted but that might be overkill, or the use of structural screws-check a Fastenmaster site for these (or GRK and maybe McFeely's).  The use of steel or plywood to sandwich between the cracked joist and the new one is another way to patch the bogus one.  I'd really need to see it to come to a conclusion.

The span on the 2x8's isn't too far, tho depending on the species and grade might be near their limit.  Bounce or sag would be one result of overspan.

The cut joist headed off might need to have the joists carrying the load to be doubled. (am I remembering the right thread here)

Another consideration are the placement of the hall walls if running perpendicular to that beam.  There might be a good bit of load not directly over that beam which sometimes gives a crown to a floor running down the hall.  And of course the size and span of the beam itself.

Your description is pretty good, I'm just descriptively challenged.

This post will help bring your thread to the top where better recommendations will be along.

Best of luck.

A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.


A Great Place for Information, Comraderie, and a Sucker Punch.

Remodeling Contractor just outside the Glass City.