Damaged Perimeter Sill Replacement

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  #1  
Old 03-14-09, 07:18 PM
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Damaged Perimeter Sill Replacement

I need some ideas and thoughts about replacing a rotten/termite-damaged perimeter sill. (Iím not sure if thatís the correct term, but every builder Iíve worked with used it or something similar, please correct me if Iím mistaken.) The following links are pics of the damaged sill and the building that sits on it:

Katana Photo Groups - Picture

and

Katana Photo Groups - Picture

The building is fairly old, but itís in better condition (structurally) than it looks and has sentimental value to myself and my church, so Iíll assume any ďideas and thoughtsĒ about bulldozing it and building a new one are just jokes.

What has me stumped is replacing more than just a few feet at a time. The sill, while providing something to attach floor joists to, supports more than just the floor. The exterior walls sit on top of the sill with only the sub-floor separating them. If I go under the building with jacks and temporary beams to prevent the floor from moving, then remove the sill, thereís an awful lot of weight resting on the (now unsupported) subfloor ends.

Some ideas Iíve come up with so far (none of which are appealing to me):

*The temporary beam, flush with the crawl-space side of the foundation wall, is assumed in all of these.

1. Build a temporary supporting post and beam wall on the outside of the building that attaches to the rafter-tails, removing much of the weight of the roof and hopefully giving the sub-flooring a fighting chance of supporting the wall. This wouldnít give me much room to work, and Iím not sure that the wall wonít sag anywaysÖ especially if the span of sill to be replaced is found to be longer than expected once more of the siding is removed.
2. Build a supporting wall on the interior that reduces weight via the ceiling joists. Iíd have plenty of room to work, but I run into the same unknowns as option 1; plus, it would involve messing up the ceiling.
3. Combine option one and two. More support, but the wall is still largely on itís own to keep from sagging out of place.

Note that a sagging wall can be corrected, but it will cause all kinds of additional repairs on the interior. Iím restrained by a very limited budget, so Iím looking for any methods that cause the least amount of damage to the building and are the least invasive; but if there's no way around cracked drywall/etc. then help me think of ways to minimize it as much as possible.

Any tricks of the trade, ideas, etc. will be greatly appreciated.

Thanks
 
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  #2  
Old 03-15-09, 08:03 PM
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How deep is the crawl space? I don't see how temporary supports inside the house reduces the weight on the floor joists that are attached to the sill. It fact, it adds weight. I would do a few feet at a time unless you can get an I beam on the foundation from one end to the other underneath the first floor joists along with the temporary outside support.
 
  #3  
Old 03-16-09, 07:38 AM
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The crawlspace isn't very deep, especially where I'll be working, but I've been in tighter crawlspaces... once I even had to fit my body between the floor joists and worm my way to the foundation wall, (I'm a bit proud of that 'cause I'm a bit on the claustrophobic side and still pulled it off ).

I don't see how temporary supports inside the house reduces the weight on the floor joists that are attached to the sill. In fact, it adds weight.
No, I don't think so, it's simply shifting the weight towards the center of the building by a few inches. As I mentioned, the floor joists will be supported from the crawlspace with a temporary beam. So it will be as though I built a second block foundation wall parallel to the one the damaged sill is sitting on. This temporary support beam will be flush with the crawlspace-side of the foundation wall.

After sitting here typing and thinking about this, I'm beginning to think that the I-beam you mentioned may serve the same purpose (in the same place, too) as the temporary support beam I mentioned, so we may be thinking the same thing, I could be wrong though.

The building is 47' long where the damaged sill is located, but two thirds of the sill or longer is still solid and structurally sound as far as I can tell, so I don't think I need the crawlspace support beam to span the entire length, do I? I hope not.

Let me know if you think of anything.
 
  #4  
Old 03-16-09, 02:39 PM
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That fact that only 1/3 of the sill has to be replaced makes it a lot easier but you still need a support under the crawl space. If it doesn't span the entire length, what are you going to use to support in in the middle?
 
  #5  
Old 03-16-09, 07:42 PM
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To support the floor joists from within the crawlspace, I plan to pour a few footers to have something reliably solid for the posts/jacks to sit on. Next, a support beam will be placed on top of the posts/jacks. The beam will run parallel to the damaged sill and as close to the end of the floor joists as I can get it and it will fit snugly against the underside of the floor joists to prevent them from sagging when the sill is removed.

The length of the beam will be greater than the length of sill that is being removed. So, the floor is going to be supported, and will remain exactly where it was before removing the sill. That's the easy part. Well, easy because of the simplicity; how much sweating I'll be doing is another matter entirely.

Since the sill bears the weight of the wall and its share of the weight of the roof, I have to come up with a way to prevent the structure from falling victim to gravity.

To accomplish this I came up with some ideas mentioned in my first post, but I think I'm going to revise it a bit. I think I'll use 4X4 posts on either side of the section I plan to remove. On top of these posts I can place a beam that is flush with the exterior side of the wall and fits snugly against the underside of the rafters where they meet the wall top-plate. This method will keep the support posts from getting in the way of my workspace. Placing the posts and the beam flush against the exterior will also allow me to mount a 2x4 horizontally between the posts and fasten it to the wall (the ends of the 2X4 will be fastened to the support posts).

In my earlier plan, the section of the wall above the damaged sill would essentially be supported only by the subfloor and the nails that fasten the rafters to the top-plate. My revised plan, with the 2X4 cross piece, actually supports the wall as well as the weight of the roof. I don't think I can come up with a better method, but that's why I'm typing on this forum... more brains working on the same problem.

The lengths of the support beams will be determined by the length of sill I end up cutting out, and the beam construction/design/material will be determined by that same distance. The same goes for the support beam in the crawlspace. If I have enough head-room at the lowest end of the crawlspace I'll be using jacks to hold the beam up, if a jack won't fit and I can't cut it short enough, I'll have to cut a 4X4 post at the correct length to keep the beam tight against the floor joists.

If I end up replacing more sill than I originally anticipated I may have to place another support post on the exterior which will get in my way, but I can manage.

I'm tired, so don't hesitate to point out anything that appears to be a flaw in my logic. Also, this isn't set in stone yet, I've got about two weeks before I can start on this, so any ideas (big or small) are really appreciated!

Thanks,
Jeffrey
 
  #6  
Old 03-16-09, 07:59 PM
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That sounds good now. I think you'll be safe that way. Give the footings enough time to set. I suppose 2 days are enough.
 
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