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Old 03-24-2013, 06:27 PM   #1
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What enginnered beam to use for sistering a joist?


I am a long time lurker and reader and now have a question I can't seem to find the answer too.

I bought a 1955 bungalow in Edmonton Alberta Canada with a 200 square foot addition with an obvious sag. I am attaching ( I hope) a diagram of the addition. The original load bearing basement foundation is on the side marked 230". The joists run parallel to the 124" mark and are roughly 16" on centre (10" joists). I scribbled some measurements indicating how much the floor sank on the exterior wall, typically 1.5" (the addition was done in 1980's, a time not known for quality work). It appears to have stopped most of the settling, but not completely (I ran epoxy on a crack where the addition joins the house and it opened up a little bit). The crawlspace is ~ 30" above grade and I foamed the exterior wall and sealed the ground with the thick plastic they like to use for this application.

So, now I want to level the floor and prevent further settling.

Plan is to rip up the floor (a hideous vinyl), sister new wood level on the joists and run a header near the exterior wall using jacks on deck blocks to take up some of the load (and help prevent further settling). I plan to use four jacks - 2 near the outer wall and 2 closer to centre (I want to make up for not pouring a pad for the blocks to be supported on).

I want to use an engineered product for the floor joists (its tough to find straight wood, as most of you know). Should I try and sister a wood I beam or a solid LVL product? I was thinking sistering a 6" product initially, but I beams look really nice and light (not that 6" 12' LVL beam should be that heavy). There is ducting and electrical work I will have to work around.

So, which beam to use? I think the deck block idea should be ok, but has anyone done this and had success or problems? Space is conditioned (heated) so not expecting a lot of movement.

Cheers,
Mike
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Old 03-24-2013, 06:39 PM   #2
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What enginnered beam to use for sistering a joist?


Jacks on blocks are not gonna hold anything. Footers would be needed to support any post. Take a few pics so we can get a complete understanding of what your trying to do. Might be able to just beef up all the joists if they are just undersized. If you have foundation settling issues (crack forming?) then you need more than just framing.

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Old 03-24-2013, 07:02 PM   #3
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What enginnered beam to use for sistering a joist?


Maybe my description is inadequate.

The flooring is above a crawlspace. The outside wall is on pier footings (I think spaced four feet) that probably sank the 1.5" do to inadequate compaction or possibly the clay in the soil or maybe from the nearby tree sucking up moisture.

It seems to be a common repair (see attached photo) using jacks to take up some of the load. The ground underneath the plastic appeared to be well compacted, I just don't see the need to dig it up and pour concrete footings (though this maybe the time to do it once I remove the existing floor).

I have not ripped up the flooring yet as I am in the planing stage (seeing post it notes from the wife with divorce lawyers and marriage counseling make me wonder if I have done too many renovations on this house already).

So, which type of engineered wood should I plan to sister to the existing joist? Has anyone had problems based on experience using jacks? This is a bungalow, so the load is not very high.

Cheers,
Mike

Note the picture is not me but taken from another website. I am a lot older and way heavier.
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Old 03-24-2013, 07:23 PM   #4
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What enginnered beam to use for sistering a joist?


what is the foundation made off opposite the wall labeled 230" (the one with the bump out)?
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Old 03-24-2013, 08:09 PM   #5
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What enginnered beam to use for sistering a joist?


It appears to be cement with some parging on it. To be honest, I am not 100 % sure. When spray foaming, it appeared to be cement. I am not familiar enough with additions, but it appeared there was a pier, guessing 8 to 12" in diameter, then a poured foundation wall (but no footing, and I could easily dig under the wall not sitting on the pier). The city probably has the original plans for the addition, but I don't.

Like I suggested, the pier support would probably have been adequate for code if everything was properly prepared. When doing work on the entrance (which was part of the addition but too low for a crawlspace), the soil appeared to be soil instead of compacted crush fill. Maybe it is allowed, but it doesn't make a good area to build over in my opinion. Ideally, they would have poured a concrete pad, but it probably cost the original owner too much.

Actually, Edmonton does tend to have clay soil, so every house I have lived in had some foundation issues (this one is a little too much for my sensibilities).

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Old 03-24-2013, 09:16 PM   #6
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What enginnered beam to use for sistering a joist?


could be a concrete peir with wood framing which was parged over.

so you are saying that the floor has settled 1-1/2" at the exterior wall (one we are discussing)?
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Old 03-24-2013, 10:01 PM   #7
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What enginnered beam to use for sistering a joist?


That is correct. The joist hangers on the basement side (or high side) have been pulled out of shape from the settlement.
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Old 03-24-2013, 10:55 PM   #8
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What enginnered beam to use for sistering a joist?


That picture you posted must be the one to show how not to do it.
Any supports to hold up a beam have to have a footer or there just going to sink like your other ones did.
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Old 03-25-2013, 02:24 AM   #9
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What enginnered beam to use for sistering a joist?


The supplier I used for reference, Basement Systems, does describe adding ~ 8 ft^3 of crushed fill to transfer the load per deck block with the floor jack to take up the load.

Not sure why the respondents are negative on the use of floor jacks - seems to be a common practice using floor jacks with the exception that the preferred base is a concrete pad. Most basements after 1970's appear to be built this way.

As I was responding to the last note, I did see how my argument of stable fill maybe breaking down. I think I will cut into the poly to take a look at the fill and see what it is like before placing the block down. I think it was some coarse crushed rock with some fine sand, but there probably is some clay soil as well. It has always been dry when I looked, but we do have a lot of snow (we had a false spring like most of North America, but with a 2 foot dump of snow in the last week on top of cold).

Like I said, it seems to have settled for the most part, this is insurance and the ability to adjust the floor 5 years down the road in case it does show signs of settling. An 1.5 inch does seem like a lot, but over 30 years, thats 0.05 inches per year - hard to detect (and likely 90 % settlement happened in the first 2 years).

Oh, I should note that when I am talking about a pier system, it is like putting a sono tube down to "stable" earth and loading with concrete. The deck pier is an addendum to help support the load the "pier" missed.

I know a helical screw system would be a great fix - but why spend several grand when a cheaper fix will work?

The problem with any system is hitting stable earth. Granddad got fed up with frost heaving in Ontario (didn't happen in England after all) that the final house was built on good old Canadian shield. Nothing like solid rock for a foundation (which ain't happening in the prairies).

Any comments on the wood to sister with? I need to make my decision on this soon (tending towards 8"LVL instead of I Joist).

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Old 03-25-2013, 09:08 AM   #10
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What enginnered beam to use for sistering a joist?


1. The addition is not big enough where you can't go fishing for straight 2x10 lumber. In fact, a little crowning will go in your favor. I joist can't be "sistered" without a lot of wasted modification and lvl is a way over engineered for you need. Having said all this, I am not sure if your joists are the problem. If your foundation system is the problem, adding more joists don't solve anything.
You may be starting out with a lot of wrong assumptions. This is a problem that a professional should look at.

2. Foundation built on piers can't be "jacked" as you imagine. You must check the piers by sight, which means digging down to where the piers end and making sure they have a footing. If the piers are not deep enough or poured without a footing, as if they were supporting only a deck, and not a wall, roof and furniture, then you must fix those piers first.
In fact, I would even check the rim joists and plates to make sure you don't have termite or carpenter ant problem. If the structure is settling, you can't assume one thing or another.

3. You can't assume the ground is firm enough to support the jacks. If they weren't dug up or filled recently, you can put down cribs (google for description) to support the jacks, but again, you are beginning with many guesses. Guessing usually means throwing money away.
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Old 03-25-2013, 09:19 AM   #11
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What enginnered beam to use for sistering a joist?


so the problem is not that your floor joists are sagging, it's that the outside wall has fallen 1-1/2". Just trying to make sure I understand your issue.
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Old 03-25-2013, 09:36 AM   #12
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What enginnered beam to use for sistering a joist?


as carpdad mentions, the sistering is confusing because it looks like your foundation ( Rim board of floor system sits on foundation) is settling and the joists that bear on the foundation connected to the rim board with hangers??? are going down with it.

please explain what exactly you are sistering to, are you wanting to sister on the outside of the house to the rim board? you cannot sister the inside of the rim board because the joists run into it.

if what your diagram shows is correct then usually a temp wall is built under house about 12" to 18" in from foundation that catches all of the floor joists and holds floor and exterior walls up and then you re work the foundation ( footing/piers, etc) and then take the temp wall down to rest the floor system back down onto newly done foundation.

ahh, just re read your original post. it looks like you want to use the temp wall idea to make it the new permanent foundation located inside of the crawlspace that holds up the floors and walls. it is doable but needs adequate footings and beam to support the load...
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Old 03-25-2013, 10:29 AM   #13
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What enginnered beam to use for sistering a joist?


I would not use the deck blocks for your columns to bear upon. There are several reasons:

1. The size of the footing (whether deck block or concrete pad) must be sized based upon the load they are to support and the bearing capacity of your soil. Apply too much weight over an area and it will settle (again).
2. Frost heave. Should you ground suffer from frost heave then the deck blocks would be pushed up causing your floor to move up. Would not be good for finished surfaces.

I would recommend installing a beam under the existing floor joists near the outer edge of the joists (preferably under the exterior wall). The beam should not be set back more than the depth of the existing floor joist. This is a US code requirement based upon having a cantilevered exterior wall. There are floor loads, wall loads as well as roof loads that the cantilevered floor joists must support. Jack up the wall/floor joists until the joists are level.

Size of beam would be based upon the span between columns and the loads they must support. Same with your footings. I would recommend concrete footing set below your frost depth. They should be sized based upon your soil bearing capacity and the column load.

I would recommend LVL or parallams over wooden I-joists. I-joists were designed as floor framing and not as a beam. It can be padded out and made into a beam per the manufacturer's specifications, but an LVL or PSL would be a much easier solution. Nothing wrong with using solid sawn lumber. I know our US codes do not require preservative treated wood in a situation like yours, however I prefer its use in exterior (even though protected) environments. I typically have the floor jacked up a 1/2" or so more than what is required for the floor to be level. This way when the treated wood dries out the floor is level.

Just my humble thoughts ....
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Old 03-25-2013, 12:20 PM   #14
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What enginnered beam to use for sistering a joist?


  • The addition is not big enough where you can't go fishing for straight 2x10 lumber. In fact, a little crowning will go in your favor. I joist can't be "sistered" without a lot of wasted modification and lvl is a way over engineered for you need. Having said all this, I am not sure if your joists are the problem. If your foundation system is the problem, adding more joists don't solve anything.
    You may be starting out with a lot of wrong assumptions. This is a problem that a professional should look at.

I can probably spend some time getting a straight board somewhere. Just seems easier to start with straight wood to begin with. The I joist sounded good until I thought about how to sister it. Of course the 2x10 actually exceeds code so LVL is only because I want the board to run flat.

Joists are not the problem – the outside perimeter wall is the problem.

  • Foundation built on piers can't be "jacked" as you imagine. You must check the piers by sight, which means digging down to where the piers end and making sure they have a footing. If the piers are not deep enough or poured without a footing, as if they were supporting only a deck, and not a wall, roof and furniture, then you must fix those piers first.
    In fact, I would even check the rim joists and plates to make sure you don't have termite or carpenter ant problem. If the structure is settling, you can't assume one thing or another.

I don’t really want to jack up the floor – I just want to add some more support in case it still sinks. I really would prefer not to have to dig down to the footing of the pier. Your comment about the pier maybe not having a footing does cause me to pause. Assuming we are at least 4 feet below ground (and really, in Edmonton, the frost line should be lower than that), it would take some digging to get down to it.

Prior to foaming, I did inspect the rim board, expecting some possible dry rot (no termites in Edmonton, no sign of carpenter ants). Looked good, though I didn’t see a sill gasket and don’t believe it was treated wood (appeared to be poly under the base of the concrete to help with water migration, though it was ripped in places). I will see more closely when I rip up the floor.

  • You can't assume the ground is firm enough to support the jacks. If they weren't dug up or filled recently, you can put down cribs (google for description) to support the jacks, but again, you are beginning with many guesses. Guessing usually means throwing money away.

It might not be that firm, which is why I wanted to add more jacks then necessary and not have to build a cement pad. I will look and see how firm it is when I open the floor up.

Gary
Gary, that is correct, the outer perimeter wall had fallen an 1 .”

Hand Drive
Hand Drive, the sistering is to make up the 1 that settled without having to jack up the existing joists (and create more issues). Sorry that I didn’t make it clear.

The joists use hangers and are connected to the rim board of the older foundation (the basement) and were distorted when the outside perimeter wall sank the 1 ”. I am sistering to the original joists. If you can visualize, I would connect the new joist parallel at one end (the joist end nearest the basement) and it would start to stick up the 1 as the joist traveled to the far end of the perimeter (the crawlspace wall). I will glue it and screw it, but this is assuming that the connection is good at the rim.

Your final comment catches what I am trying to do.

Gary

  • The size of the footing (whether deck block or concrete pad) must be sized based upon the load they are to support and the bearing capacity of your soil. Apply too much weight over an area and it will settle (again).

That really is the crux of the problem, is the soil any good when they poured the pier. I assume they sized it correctly and let’s face it, it is a small addition. A simple load calculation (50 pounds ft^2 floor, 60 pounds roof^2 roof, 10 pounds per foot ^2 wall) suggests max load of area is 4600 pounds. Normally, you split the load between walls (and there are 3 support walls in the diagram), but lets give the outside perimeter 50 % or 2300 pounds – not a huge amount of weight. I shouldn’t ignore the “pony” wall which sits on the piers – maybe make the weight 5,000 pounds. Wouldn’t you know it – can’t find the darn reference book with all the requirements. It shouldn’t take too much of a pad to meet requirements.
  • Frost heave. Should you ground suffer from frost heave then the deck blocks would be pushed up causing your floor to move up. Would not be good for finished surfaces.

Where I am placing the deck blocks is heated space, so frost heaving is unlikely now. Frost heaving on the piers may have happened in the past, but is less likely now that I heat the area (though -30 C, all bets are off).

I am not going to jack up the floor to level – it could create other problems. I am going to level the floor and try and prevent further settlement.

I will go and look for some straight lumber. I can always plane out high spots and fill in low – just thought it might go faster using LVL. I typically have been using treated wood (Blue Wood), but they only offer 6”, which should be good enough for sistering to the current joists (which are in good shape).


Thanks for the input.

Mike
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Old 03-25-2013, 12:28 PM   #15
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What enginnered beam to use for sistering a joist?


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I typically have been using treated wood (Blue Wood), but they only offer 6”, which should be good enough for sistering to the current joists (which are in good shape).
Mike I'm lost, you say your are sistering to the current joists?????? from what you said the joists are not your issue it's the settling of the support of the joists and exterior wall, or am I missing something???

you can use LVL for the beam/header if you like, nothing wrong with that. You have to come up with a beam and column system. the wider the spacing of the columns the deeper the beam and vice versa

if you're not concerned about the existing 1-1/2" drop then butt your new beam/header under the existing floor joists and secure with your columns. I'm not recommending the deck blocks, but if you feel comfortable with their use that's up to you. Hopefully you won't have any issues.

post back with any questions or comments

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