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Would it be reasonable to just pour concrete in a tube down to 30-36" and then leave it above grade to the height where I want to sit the rim joists and joists? What appears to have been done was to pour a 6" diameter footing and then pour a 5" thick 12" dia. pad. The column above is not centered over the footing and it would seem the footing settled in some cases. I'm inclined to pour a 12" footing and just sit the framing right atop that. That assumes I can get the footing leveled off at the right points. I suppose a PT 2x could be sit atop the footing to make up for an inch here and there.
The other issue with mine is they ran the column to the footing and then attached the framing to the column. Now then -- perhaps I can use the existing footings -- just shore them up where needed, and sit my framing on them, and then the columns on the framing. That might indeed be an idea. The framing would apply a more even distribution of weight onto the footings.
To answer your first question, yes. The only problem I see with that is that if left exposed, the round concrete pier might not fit with the style of your house. If the outside 2x is at the outside edge of the footing, then you could just cover the whole section to grade with PT lattice and it would not show.
That is a lot of concrete so you probably will want to have it delivered instead of mixing it yourself.
As long as you are in compliance with codes, you can do pretty much what ever you want. BTW, if you use any wood that is not PT, such as the T&G floor, be sure to prime all six sides and I would even topcoat all six sides, although some may disagree with the topcoat part as it will keep the wood from breathing.
Good point -- I'd have to accurately align new footers/piers such that they align with the outside edge of my framing. In my case, the rim joist sits pretty close to the ground, maybe 12" and we have shrubs all along that area, so it would be hard to see the footers/piers. But you do raise a very good suggestion -- maybe I can keep my existing footers (6" dia I think)- assuming they are solid - and just buildup new piers, using blocks as you did. Even though in my existing case the problem is that the columns do not align atop the piers, if I reframe, then the framing will more evenly distribute the load, so the tipping, etc will be eliminated. Then I sit my columns atop my floor.
It looks like they poured a 6" dia. footer, and then that 12" dia. x 5" thick pad atop the footer. It looks like the pad was poured to a certain height, so in some cases the pad was only a few inches, if that, thick over the footer. In the photos you can see a few were the footer is poking up through the pad - or in reality most likely, the pad settled down over the footer. In most cases I can easily pull out, or chip away those pads.
So if I put some blocks (as you have) atop my footers, I may need to shim up to some height. Would PT 2x or 1x be OK for that. So footer (6" dia. concrete)-- block (just sitting atop the footer) - some PT "pad" - then framing. Do I need to secure the pier blocks to the footer? It's still going to be hard to get block or other pier to sit securely on that small diameter 6" footer. But certainly putting the framing atop the pier, and then the column atop the floor will greatly help with weight distribution.
I think I would knock off the old pads but leave the footers, as long as they are stable and don't tip. Then I'd drill some 1/2" to 5/8" holes in the tops down about a foot using a masonry bit and a hammer drill, good excuse to buy tools eh! At least 4 holes. I'd insert rebar into these holes with some hydraulic cement to hold them.
Then carefully measure the height from the bottom of the rim joist (planned bottom, be sure to allow a little slope on the porch deck to drain water) to allow for the concrete block. I suspect that you will use one regular block and one cap block for a 12" height plus about a 1/2" seam for mortar at the bottom and between, 13" total. Frame up a pad 13" below the planned bottom of the rim joists.
If 13" will put the pad below grade, then plan on just one block with a 1/2" mortar seam so that will be 8.5" below. Bent the tops of the rebar as needed (outward along the long dimension of the pad, and pour the concrete. The pad should be proud of the block by about 2" so it will need to be 10 x 20.
Here is an alternative to consider, there is a precast concrete pier, but it is only about 8" tall. You could follow the above for the poured pad, but 12 x 12" and use it instead. You would not need to mortar it down but you could. The top has groves for 2x and a 4x4 in the center. You can set the block and then either run a short 4x4 PT up to the level of the rim joists and bolt them together (do not nail, use good bolts) or If they are at the right height, you can just lay the 2x in the grove. Using the 4x4 PT gives you some wiggle room to make sure the deck is perfectly level and this could be the easiest way overall.
OK, think I mostly got it.
So I could possibly save the footers (and a LOT of work). I attach a pad to them by using rebar. I install 4 pieces of rebar vertically into the footer and then bend it out. Something like this:
Then I use 2 x something and frame up a pad around that. How thick should I make the pad? I guess it partly depends on the gap between pad and desired rim joist, but I can dig away to make the pad 2x6 thick. That is what it appears they tried to do -- minus the rebar. So with this I'll have a pad that is tied to the footer. If I opt for the block (or block w/ cap), then do I position the pad where the block would go relative to where my rim joist will sit? Recall my problem now is the columns are not directly atop the footer; rather they are off by a bit. So I might end up more like this:
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I would not necessarily bend the rebar like that, but my point is the pad would not be centered directly atop the footer. If I need to center, then maybe I need to make a pad that is 14 x 20 since the block may sit off to either the inside or outside of the footer by a few inches. (It would be centered on the pad, but the pad would not be centered on the footer.)
If I use the block approach, it seems I'd want the outside edge of the block to sit flush with the outside edge of the outer rim joist. The block seems like a solid approach, as I could use a double 2x8 rim joist and then also bring over a double 2x8 joist atop the block, like this:
The plans actually show a double rim joist and a triple joist, with then single 2x8 blocking. I'll have to look at the details, but triple 2x8 seems a bit overkill.
Thoughts -- would I be better off with a 2x10 rim joist? or double 2x8? I guess I'm thinking if I can use 2x8 everywhere it might be simpler. And I'm thinking the double 2x8 rim joist my be overkill also. Those blocks will support 16" of the rim joist and the ends of my joists. My largest span is 120" -- from the center of one column to the outside edge of the corner column. So with the 16" blocks, that is 120-16-8 or 8' of span with no support. The column is going to be right atop the block, so none of it's weight is transferred to the joist span.
In fact, looking at your pictures, I'm wondering if I could use a single 2x8 rim joist and then 2x6 joists with 2x6 blocking. That said, keeping my joists the same as the rim joists would allow both to sit on the blocks - that seems to be better. I will probably position joists at both edges of each block, and then in between as needed to come to some sort of consistent blocking dimension. On second thought I probably should position the joists over the blocks where the columns will sit. In fact, that probably explains why the original plans had triple joists -- 4.5" wide, so that most of the column would sit directly atop. So 2x8 for rim joists and joists probably makes the most sense -- with maybe 2x6 blocking it the cost difference is really that significant.
Hmm.. now I wonder if I should try to keep some of my existing framing? Or tear it all out and start over with PT only? I still cannot believe they did not use PT. Around here PT is sometimes even less than untreated.
The blocks look to be 16x8x8h and a cap is 2h, so with 1/2 mortar joints, the "pier" would be 11"
There are 2" thick cap blocks and 4" thick cap blocks. In my experience, I have only seen the 2" cap blocks in non structural use, like landscaping, but I don't know if that is a rule or anything.
I would center the pad directly over the footings, if not, you risk tipping. Then build the piers directly on top of that. The columns should sit on top of the decking, so they can be offset from the piers like mine are. If they are within a foot of the pier, then a double 2x8 should be fine. On my front porch, I have one column that is about a foot away from the pier and I used double 2x8's there and after 10 years, there is absolutely no sign of sagging.
I would double the rim joist no matter what size you use. The outer rim joist will be subjected to more weathering than the inside one, so in the event that it has to be replaced, you won't have the do any jacking of the roof and deck removal to replace it.
I found this link, but like anything on the internet, you will need to decide if the information is accurate and valid. Since anybody can post anything they want without editorial or peer review, I take any web site with a grain of salt.
According to table 3, you can get by with 2x6 PT. Your plans probably were drawn up with white pine in mind which I think is not quite as strong. Table 3 is for 16" joist (blocking) spacing. It looks like I undersized mine a bit as my spacing is 20", so I would have to go by table 5. Oh well.
I would still use at least the double 2x8 for the rim joists, but it looks like you can use the 2x6 for all your joists. I only used double 2x6 for my joists that go from the ledger to the rim, but triple probably would be better. I did my front porch at least ten years ago and it is just as solid today as when I built it and a lot more solid that it was when I bought the place. BTW, the place was less than 5 years old when I bought it but the porch was untreated white pine and only had single 2x6 joist from the ledger to the rim and double 2x6 rim joists.
It appears that the above website has a lot of links that you might use. It also shows making piers from 4x4 or 6x6 PT, so that is another option, but you will still need a pad that goes above grade and you will still need to drill holes for the rebar in the footing, but you will also need those base things to tie down the PT posts so that may mean embedding some type of threaded rod into the pad when you pour it.
As for the thickness of the pad, 4" is minimum. You can go thicker if need be to get the pad from the footing to the grade. If you do go with a PT post (pier), you should probably have the pad at least 2" above grade and be sure to ever so slightly bevel the top so that water will always drain off and not sit.
OK -- so ideally the pad is centered over the footer -- the block is centered over the pad -- and the rim joist is centered over the block. I suppose the rim joist could sit on the outside edge of the block so that it is flush, and also that would allow more room on the inside of the block for the joists to also rest. I can use joist hangers also, but having those joists sit on the block will add even more rigidity.
I guess in reality it would be best if all the downward force is concentrated into the center of the footer. So however I align pad, block, framing should result in this as close as possible. The issue now is my columns rest directly on the pad, which is not centered over the footer. So the pads have tipped, cracked, etc. I have a few where something sank as there is a gap between column and pad. If the footer is good, I can pour a new pad to fix all this. When I rest the columns on the joists, that should help with distributing the load, even if I'm an inch or two off center, it will be better than what I have.
Well -- I'm hoping I can be an inch or two off center here and there and be ok. If -- big if -- but if I pull up this entire floor and redo it, I will run my t&g flooring perpendicular to the house (it's parallel now). Perpendicular gets the water channeled into the small t&g grooves and out to the end of the floor. As it is, the water sits in the parallel grooves. Flooring typically comes in 8' and 12' lengths, so that is why a 6' floor is important -- I can cut the 12' board in half. On the north and south side I need to cover 74", so I'm thinking to run one floor board at the house parallel to the house and then all others perpendicular. On the east side my current measurement is 71", so I'm ok either way, but I may want to run that first board parallel also so I can get a good caulk seal along house and floor. But if I frame up a new floor, I'll have an inch or so of adjusments I can make. It will come down to keeping the columns as vertical as possible. I have a few now where they are visibly off by an inch or so. I guess generally I'm hoping I can frame the flooring such that the floor is around 72" so my 12' flooring boards work out.
Regarding joists. I'm assuming the joists are what run perpendicular from ledge (at house) to rim joist. I was going to space those about 6' apart or so --or-- just at the piers. (My plans show a triple joist at each pier). Then in between those, run blocking parallel to the house. Maybe those are also called joists also, but they are just supported by the joists that run from ledger to rim joist.
Here is a sketchup of the idea.
My sketchup shows a few issues - albeit minor I suppose:
- the rim joists are not centered over the footing. Not exactly but pretty close, The rim joist needs to sit on the outside edge of the block else it will look bad. The block is centered on the pad, and the pad is more or less centered on the footer.
- the corner is not centered over the footing either -- and in fact, it would appear that I really need more than a 6" footer on those corners. I might have decent footer in-place as those seem to be the more solid ones.
That said -- this is probably about what I would be doing. There will some slight off-center alignments. If I center the rim joist over the footer, than the block and pad will be offcenter.