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Homeowner Forum / Construction / October 2006Post replacement question
Good evening. I have a doubled 2x10 joist in my basement with a 4x4 post supporting it partway along its span. The post carries quite a bit of weight, as evidenced by the fact that it has crushed the wood along the lower chord of the joist by about 3/16". The post is also not fastened to the basement floor, so I am not happy with this arrangement. The doubled joist runs parallel to the other floor joists; it is not a beam that supports the joists. But it is critical, as there is a loadbearing wall directly above and parallel to it. I want to replace the post with a loadbearing wall. My question is, how can I safely support the joist (and the loadbearing wall above it) while I do this? Thanks -Mark > Good evening. > [quoted text clipped - 14 lines] > Thanks > -Mark how about incorporating the 4x4 into your new wall? > how about incorporating the 4x4 into your new wall? I was thinking the same thing. Is there a reason you can't leave it in place and build your wall with it? > > how about incorporating the 4x4 into your new wall? > > I was thinking the same thing. Is there a reason you can't leave it in > place and build your wall with it? I'm thinking along the same lines (great minds...??? :) ) But, to avoid simply a "me too" post, I'll add another suggestion that before enclosing the post w/ the wall, raise the beam and insert a piece of 1/4" or maybe 5/16" steel plate w/ flanges for fastening to post and beam and a foot or so long to help distribute the present point load. >> > how about incorporating the 4x4 into your new wall? >> [quoted text clipped - 8 lines] > post and beam and a foot or so long to help distribute the present > point load. > But, to avoid simply a "me too" post, I'll add another suggestion that > before enclosing the post w/ the wall, raise the beam and insert a > piece of 1/4" or maybe 5/16" steel plate w/ flanges for fastening to > post and beam and a foot or so long to help distribute the present > point load. Hmm. . .I like that idea. Is this an off-the-shelf item, or would I need to have it fabricated? In reading back over my post, I find I was not quite accurate. I actually want to build a loadbearing wall from the vicinity of the post to one end of the beam. The beam runs parallel to the basement stairway, and the post is adjacent to the bottom stair. The wall would enclose the stairway. So. . .the existing post (or a new post placed within six inches or so) would be at the end of the wall. The bearing plate sounds like a very good idea in this situation. Also, should I consider something sturdier than a 4x4 in this application? Thanks -Mark > > But, to avoid simply a "me too" post, I'll add another suggestion that > > before enclosing the post w/ the wall, raise the beam and insert a [quoted text clipped - 15 lines] > Also, should I consider something sturdier than a 4x4 in this > application? Quite likely wouldn't find the ideal prefabricated, most if not all of the readily available hangers and connections aren't heavy enough material to take the end load w/o simply bending and so wouldn't do much to distribute the load along the beam away from the present point. If the present 4x4 doesn't show signs of stress, probably don't need more, but certainly couldn't hurt. What you might consider that could help w/ the compression problem as well if you get it the right length so it actually shares load would be to put a second 4x4 beside the present one w/ the plate over both, of course. That would double the surface area below and make the plate load-spreading more effective by reducing bending moment on it and still enable a smooth wall end of uniform thickness. > > > But, to avoid simply a "me too" post, I'll add another suggestion that > > > before enclosing the post w/ the wall, raise the beam and insert a [quoted text clipped - 4 lines] > > Hmm. . .I like that idea. Is this an off-the-shelf item, or would I need > > to have it fabricated? ... Oh, another thought just after I sent my last response--one pretty simple way that is _probably_ as good structurally as what is presently done (if the current post simply has a toenail or two in it and better if it's simply just sitting under the beam as it sounds like it might be) would be to drill holes through the plate and simply drive a couple spikes into the end of the post and then when in back in place, into the beam. A flange, of course, would be better, but if there's nothing there now, even this would exceed that. > Quite likely wouldn't find the ideal prefabricated, most if not all of > the readily available hangers and connections aren't heavy enough > material to take the end load w/o simply bending and so wouldn't do > much to distribute the load along the beam away from the present point. Yep. I made a few calls, and no one has what I'm looking for. Off to the local metalwerx I go. . .I can only imagine what this is going to cost. :-( Since I'll be coughing up cash for a custom-made bracket, any suggestions on features I should incorporate? > > Quite likely wouldn't find the ideal prefabricated, most if not all of > > the readily available hangers and connections aren't heavy enough [quoted text clipped - 7 lines] > Since I'll be coughing up cash for a custom-made bracket, > any suggestions on features I should incorporate? > I have a doubled 2x10 joist in my basement with a 4x4 post supporting it > partway along its span. Follow-up question: The existing 4x4 post rests directly on the slab. I suppose there _may_ be an under-slab or integral-slab footing, but I doubt it. This is seventy-five year old construction. If it were _your_ house would you add a post footing and bracket as part of this project, or just rest the new post on the slab and secure it to the slab with an appropriate anchor bracket? And if I rest the post on the slab, should the post be treated lumber? Thanks -Mark > > I have a doubled 2x10 joist in my basement with a 4x4 post supporting it > > partway along its span. [quoted text clipped - 13 lines] > Thanks > -Mark Mark- Sounds like you've been thinking about all the issues & options. End grain of a post onto a slab is not a great idea there are a couple of ways to go instead. Treated post, just "treat" the end of an untreated post (dry wood end grain really sucks up any treating chem you might choose), a sturdy mechanical post base (the only one, IMO, worth the work to install is the Simpson EPB44 Not the EPB44A!) a treated "sill" under the post or one of those pier blocks with the treated chunck of wood on it. My dad & I "fixed" rotted end of a covered patio corner post thus way (30 years ago & it's still fine). The original install had the post going down onto a patio slab. SoCal weather took about 15 years to rot a few inches of the post. Back on your 4x4 to 2-2x10 connection Simpson makes some off the shelf post beam conectors most are really thin but on style is 1/4" The CC3 1/4-4 is made from 1/4" material & is 11 inches long. It might to the trick. If it was my house.... I'd use the EPB44 & the stock post cap CC3 1/4-4 cheers Bob In a previous post Bobk207 wrote... > Treated post, just "treat" the end of an untreated post (dry wood end > grain really sucks up any treating chem you might choose), a sturdy > mechanical post base (the only one, IMO, worth the work to install is > the Simpson EPB44 Not the EPB44A!) Bob: What do you think of the Simpson ABU series? That's the one I usually specify. Works especially well in a retrofit situation.  SignatureBob Morrison, PE, SE R L Morrison Engineering Co Structural & Civil Engineering Poulsbo WA bob at rlmorrisonengr dot com > In a previous post Bobk207 wrote... > > Treated post, just "treat" the end of an untreated post (dry wood end [quoted text clipped - 13 lines] > Poulsbo WA > bob at rlmorrisonengr dot com Bob- The ABU type is fine in dry (inside locations), I tend to be really paranoid about dry rot....I've seen a lot of installations where Simpson bases result in rot. IMO the only decent base for exterior (& WET) installations is the EPB series. Even ones with the 1" standoff (code min) IMO do not allow for adeqate drying. The bases that have a thin plate (or even the thick one) are not at all moisture tolerant. cheers Bob K > Treated post, just "treat" the end of an untreated post (dry wood end > grain really sucks up any treating chem you might choose), a sturdy > mechanical post base (the only one, IMO, worth the work to install is > the Simpson EPB44 Not the EPB44A!) I'm planning to use a 4x6 post (paranoia rules) so I believe the EPB46 is in order. So do you propose that I cut a hole in the slab and pour a proper footing? This bracket is designed to be embedded into a concrete pour. I have no problem with doing that. . .I could drill a ring of holes with my trusty Bosch rotary hammer and break through the slab. What's a good concrete mix formula for a post footing? This might be my excuse to buy a power mixer. . .I have several concrete projects in the pipeline. I'm really tired mixing by hand in the wheelbarrow. > The CC3 1/4-4 is made from 1/4" material & is 11 inches long. It > might to the trick. > > If it was my house.... I'd use the EPB44 & the stock post cap CC3 1/4-4 CC3 1/4-6 looks like the ticket. According to the Simpson site this bracket uses 7 gauge steel (a bit less than 1/4") but it's probably sufficient. I'll try to find out who can order one around here. It certainly has to be cheaper than having something fabricated. Hmm. . .the CC3 1/4-6 only supports 19,200 pounds of download. Do you think that will be enough? :-o Thanks for your help! -Mark > > Treated post, just "treat" the end of an untreated post (dry wood end > > grain really sucks up any treating chem you might choose), a sturdy [quoted text clipped - 28 lines] > > -Mark Mark- Coming from the "king of overkill" (me) this might be a little funny but............... I think you might be over doing this retrofit :) There really is no benefit to putting extreme over capacity into this system....esp if a single element controls the behavior. I think Bob M. will back me up on this but a 4x4 is plenty of capacity plus you only to handle the load that is brought to the post by the 2-2x10. So what is the design dead load & live load for the area service by this post? IMO no need for a 4x6 if you use the post cap to spread the load into 2-2x, the allowable direct bearing (at 425 psi) from the 4x4 to the 2-2x is about 4400 pounds, using the CC3 1/4-4 (which btw if I read the rather confusing catalog correctly is 1/4" material) would boost bearing capacity substantially. I would just add the CC3, reuse the 4x4 you've got & install an EPB44 (or use the ABU if the basement in nice & dry) . The existing slab is probably ok but again you've got the know the load & estimate the slab capacity (it's working now, right?) cheers Bob ... > I would just add the CC3, reuse the 4x4 you've got & install an EPB44 > (or use the ABU if the basement in nice & dry) . The existing slab is > probably ok but again you've got the know the load & estimate the slab > capacity (it's working now, right?) Thanks for jumping in and pointing out parts--I don't do this as a rule so didn't have an actual place to point Mark to. (And, I filed away the names for possible future reference, so that's good, too! :) ) Anyway, if Mark is still concerned about point load long term on the slab he could do the same thing as at the post cap--just lay a plate (say 1-ft square) on the slab under the post to distribute load. I forget whether he said whether this is (relatively) new house or old so don't know whether to think "working now" implies "continue to work w/o a crack developing". > If it was my house.... I'd use the EPB44 & the stock post cap CC3 1/4-4 Bob: The EPB46 (the 4x6 equivalent of the EPB44) looks like a good choice for an exterior application, since the bracket is welded to a pipe which can project up out of the concrete pier, and that would keep the bottom of the post clear of any surface moisture. However, it is only rated for 3465 pounds of downward load, which would be insufficient for a basement support column. http://www.strongtie.com/products/connectors/EPB.html The CB46 seems to me more appropriate for a basement column. Simpson does not list an allowable downward load for the CB46; presumably the bracket itself would not be the failure point if the downward load were too great for the system. http://www.strongtie.com/products/connectors/LCB-CB.html The CB46 does not offer the same wet-location protection as the EPB46, since the post sits directly on the concrete pier with only a plate of 7ga steel separating them. But I don't see that as a problem in my application, especially since the concrete pier would be 1-2" higher than the surrounding slab. Am I overlooking something here? Thanks -Mark In a previous post Mark wrote... > The CB46 does not offer the same wet-location protection as > the EPB46, since the post sits directly on the concrete pier [quoted text clipped - 3 lines] > > Am I overlooking something here? Mark: I often specify the ABU series, but also specify that the stand-off cup be filled with non-shrink grout to increase the load capacity of the the base. This is not in Simpson's literature, but it works. Other than that your analysis of the column base types is correct. The only other option is some sort of custom designed and fabricated column base. SignatureBob Morrison, PE, SE R L Morrison Engineering Co Structural & Civil Engineering Poulsbo WA bob at rlmorrisonengr dot com |
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