# Sistering joists and getting floor level



## Nealtw (Jun 22, 2017)

Use floor glue it will stick. Tie a string across the top of level 3/4" above the highest joist. set the joist in with s 3/4" block sitting on top and raise until the block touches the string and drive a screw right below the string, remove block and set go set the other end the same way. Then drill and place your bolts. 


The hole, I will just call the end blocks doubles , measure the distance between the joists and cut 2 blocks and screw them to one end of the doubles on the ends of the hole each with 6 or 8 screws.
Install a single across the hole with 4 screws sideways into the blocks and 4 screws and 4 screws toe nailed into the doubles.


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## jaketrades (Mar 2, 2017)

I measured out the difference in level on the joists. From the entrance of the bathrooms to the back wall (brick wall) the drop is about 1 1/2”. My previous picture was incorrect. 

I did some quick math (See below) to see how much higher the finished bathroom floor will be than the common area outside the bathroom. If I use two layers of 3/4” sub flooring (advantech and regular plywood), the height difference is almost 2” (1 15/16”). That gap seems rather large. If I only use one layer of plywood (Advantech) the difference would be 1 3/16” which seems to be within the acceptable range.

One bathroom will have a bathtub ($400 kohler variety), toilet and vanity. The other will have a glass enclosure shower, toilet and vanity. There will be a closet in the bathroom area with a stacked washer dryer.

Is one layer of plywood adequate support? 


getting floors level 1 8/16
plywood base 12/16
plywood top 12/16
cement board 4/16
mortar 2/16
tile 5/16

Total 3 11/16


Exisiting subfloor 14/16
Hardwood floor 12/16
cushioning material 2/16
Total 1 12/16

step up 1 15/16


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## Nealtw (Jun 22, 2017)

jaketrades said:


> I measured out the difference in level on the joists. From the entrance of the bathrooms to the back wall (brick wall) the drop is about 1 1/2”. My previous picture was incorrect.
> 
> I did some quick math (See below) to see how much higher the finished bathroom floor will be than the common area outside the bathroom. If I use two layers of 3/4” sub flooring (advantech and regular plywood), the height difference is almost 2” (1 15/16”). That gap seems rather large. If I only use one layer of plywood (Advantech) the difference would be 1 3/16” which seems to be within the acceptable range.
> 
> ...


 There is one more trick left from years ago when they did a mortar base.
Add to the sides of the joist lower 3/4 and sheet between them. 
Same procedure as discussed above just lower the sister another 3/4" and add to both sides of the joist.


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## jaketrades (Mar 2, 2017)

Okay I'm finally getting around to sistering & leveling the joists. 

I started leveling to get a feel for the process today. Just two screws into the old joists for now. Will sandwich and bolt /glue next. See pics.


1. Why is gluing sisters to the original joists important? I've glued and bolted in the past but never understood the gluing part ....

2. When bolting (bolt/nuts/washers) on sister's what should the distance b/w bolts be? I've heard an up and down pattern is best when bolting. Some bolts high and some low.

3. I'm going to sandwich the old joists with two 2"x8"x8's. Pic below shows the center on center of the old joists were all over the place. Ranging from 11" to 17 1/2".











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## carpdad (Oct 11, 2010)

Glue and bolts add more strength but your application should be fine without the glue and bolts. Glue when decking adds cushioning. Is the spacing still 18" when joists are added? 16" oc is the rule. If you are worried about the inspection, just add another joist, even if 2x4. Think about how you're going to get a tool in the space. Pre nail and palm nailer, longer wood screws at an angle, pre screws and angle drill. Nail or screws from the other side.


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## Nealtw (Jun 22, 2017)

You could go a little thicker plywood out just add a 2x4 to the other side of the joist. 
Glue is only important if you think some one will take it apart and you really want to piss him off.


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## jaketrades (Mar 2, 2017)

Another thought... am I better off sister with 3”x8” material vs 2x8”.

The 2x8” I temporarily installed feel flimsy in comparison to the original 3x material.

@carpdad the new OC measurement will be within 16” with my 2x plan. And I’m borrowing my friends right angle drill for the job. But great call on the palm nailer. Just googled it.





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## Nealtw (Jun 22, 2017)

Don't worry about the flimsy feel of the 2x8, the plywood fixes that. I would get busy with a nail gun they fit in 11 inches or maybe a little less.


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## HenryMac (Sep 12, 2018)

The other advantage of glue is it helps prevent squeaking. But unless you take a disc or belt sander and cleanup the sides of the existing joists the glue isn't going to be worth the effort.

You might want to consider using HeadLOK screws, installed with a cordless driver. They are pretty amazing. I've used them for various projects since we used them on our pole barn in 2016.

https://www.amazon.com/FastenMaster...=2025&creative=165953&creativeASIN=B001OEJULG


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## 3onthetree (Dec 7, 2018)

There are 2 different problems here, and probably need 2 different solutions.

1. The plumbers notches - these need a full sister of 2"x8" at least 3' each side of the notch. Bear on one end and I'm estimating from the pic 6' out will extend far enough. Block perpendicular at the open end of the 6' long sister in every joist space. This is only to prevent the 3"x20foot from failing at the notches (level is a bonus).

2. Unlevel 3"x20footers - sagged in the middle 1 1/2" over 100 years? Sandwiching each with (2) 2"x8"x12' seems to be adding too much unnecessary weight. Note that any length of 2"x8" is not structural because it is not bearing at both ends. Even if you could go 20', (which you say you can't) that is too big a span for a 2"x8" structurally. So, you can level the remainder of the 3"x's much simpler than your pic: sister a 2x4 or scribe a 2"x_ on top. And add another row of perpendicular blocking 12' out to minimize any future sagging.


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## jaketrades (Mar 2, 2017)

3onthetree said:


> There are 2 different problems here, and probably need 2 different solutions.


I scribbled on a picture of the joists to make sure I understand completely....

Blue line = sisters
Purple lines = perpendicular blocking at the end of the 6' sister.
Green line = 2"x8"x10' screwed perpendicularly along the bottom of the joists to transfer load across all joists
Orange line = small blocks inserted into the notches

1. The plumbers notches - Are the purple lines what you mean when you say insert perpendicular blocking? Does a board (green line) underneath the joists help transfer load across the joists. I have about 30" of space under the joists in the bathroom area (up to about 5' off the brick wall). Below that is another bathroom.

Does inserting small blocks (orange line) in the plumber's notches prevent the original joist from bowing inwards.

When I run the sisters along each side of the plumber notched joists, should I run flush with the original joists and then use the method outlined in #2 of your post to achieve level? Or should I run the sisters to achieve level?


2. Unlevel 3"x20footers -I really like the idea of scribing a 2x4 across the top of the joists and cutting the 2x4 to make a giant shim.

If I was to sister I would be adding 42lbs to the joists. Doesn't seem like a lot but why bother when I can shim the exisiting joist. 2x8x8' = 21lbs. I'm only leveling out to 8'. That's where the bathroom ends.

Now I've got to figure out how to cut the giant shim. I'd need to cut the 2x4 lengthwise along it's 3 1/2" side. My circ saw maxes out at 2 1/2". 2 passes with the circ could do it. Table saw maxes at 3".... not even sure a table saw can make that cut. A friend has a larger circ saw (10") - I'm leaning toward borrowing his saw.

Thanks a lot.


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## Nealtw (Jun 22, 2017)

The block at the bottom of the joists can be 2x4 if they are even needed after all these years.


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## 3onthetree (Dec 7, 2018)

It'd be nice to get the new wood to bear on that party wall, but do I see the neighbor's joist popping thru? I'd foam that wall to seal it, and wondering about how you're achieving a fire-rated shared wall (are you putting 2 layers 5/8"X GB on a continuous separate wall 1" away from the brick?). 

The main assumption is that the 3"ers are structurally sound. If it was me, I'd rip up the whole subfloor and put 2x12x20' sistered to each - smooth subfloor, smooth high ceiling below, structure still intact. And design all 3 floors to maybe introduce a bearing point somewhere along the 20' all the way down to a post footing.

Your drawing is pretty much there: 

The "orange" tetris blocks aren't important - it doesn't have a keystone-in-an-arch effect, but if it makes you feel better about it do them.

The "green" continuous 2x underneath only prevents twisting, not needed as Neal said after 100 years. 

The "purple" solid blocking in between is what will spread the load somewhat. So I would split the 20' span in thirds and run blocking the whole length of the building. Those can be end-nailed into the "blue" 6' sisters as well.

The "red" shims are stood on 1 1/2", not flat, so just rip with your circ, glued and screwed (the subfloor doesn't need 3 1/2" to bear on. If you're worried about the 17"-18" joist spacing in spots just add blocking underneath). Attached a photo of a circa 1905 bathroom I'm working on same flavor as yours needing shims.


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## jaketrades (Mar 2, 2017)

Thanks for the post @3onthetree. 

I spent New Years Eve figuring out how to cut that giant shim and I found a pretty cool video on how to do it. 



.

I measured the high and low points on a joists and marked them onto a 2x4. I cut the 2x4 into a shim on a table saw using the technique in the video. Very straight forward. (I cut the 1 1/2" wide side).

The problem arose when I went to fit the shim on a joist. I chose a joist that wasn't too dinged up or so i thought. The joist had small peaks and valleys and was twisted. Then I reread your post and realized I need to scribe the joist not just measure the highs and lows.

I had to make some progress so I started sistering joists. I was able to get about 1 1/2" of the sister onto the party wall in most cases. I did bash in a brick or 2 to get more purchase where none was available. 

All was coming out nicely until I got to the super twisted joist (Joist 2 or J2). I clamped on a sister and shimmed it out to get it level. Two questions: Can I sandwich J2 with two sisters and get her to straighten out? Or I am better off with one sister to the left of J2 with small wood blocks in the gaps b/w J2 and her sister?

I'm going to revisit the giant shim technique for Joist 5. Would be nice to have that in my bag of tricks for the next leveling project.

I'll install the blocking at the open end as you suggested.

Regarding the brick wall, good tip on foam sealing the openings. And yes the plan is to use one layer of 5/8" sheetrock, and then either 5/8" green board or 1/2" cement as appropriate. I'll probably be 2" off the brick wall b/c of where the venting is coming up.

My legs are super sore. Sistering joists is a great workout.


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## 3onthetree (Dec 7, 2018)

Always one pi$$er in the bunch, eh? If you can twist J2 back without twisting the opposite end with it, nice to meet you Clark Kent. You're probably fine since you're bolting the sister, just solid block between J1-J2-J3 both sides of the notch. However, just 3 bolts running midpoint along the 2x8x8 isn't doing anything structurally but just holding the sandwich tight to the 3"er. If you have a framing nailer it may be easier to toenail the sisters (min 3 high @ 12o.c.).

A good investment you'll earn back in time saved is a laser level. It's hard to find a good starting point for square and plumb in these old structures, and quicker than a level when you're shimming rough wood that long of a length.


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## jaketrades (Mar 2, 2017)

3onthetree; said:


> Always one pi$$er in the bunch, eh? If you can twist J2 back without twisting the opposite end with it, nice to meet you Clark Kent. You're probably fine since you're bolting the sister, just solid block between J1-J2-J3 both sides of the notch. However, just 3 bolts running midpoint along the 2x8x8 isn't doing anything structurally but just holding the sandwich tight to the 3"er. If you have a framing nailer it may be easier to toenail the sisters (min 3 high @ 12o.c.).
> 
> A good investment you'll earn back in time saved is a laser level. It's hard to find a good starting point for square and plumb in these old structures, and quicker than a level when you're shimming rough wood that long of a length.


Few more questions 

Joist 2 - having the sisters spaced off Joist 2 to accommodate the twist is acceptable? 

Fasteners. - when you say min 3 high @12 OC - does that mean 3 fasteners in a vertical line every 12”

Nail gun - Don’t have a framing nailer. Would #9 3” deck screws suffice? 

Toenail - do all of the fasteners go in at the same angle (20 degrees) or do you want to vary the angle?

Laser - I have a laser and used it to draw a line on the back wall, but then wasn’t sure how to use it to get the sisters level. The laser’s beam is 3” off the ground. 







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## Nealtw (Jun 22, 2017)

Set the laser somewhere and measure down from the light to the fixed area. 
Or just mark a stick at the line. lift the sister with the stick on top. When the light is at the line you are level. Nails are better but just add more screws to get the same effect. Hard to imagine you overloading 30 screws per board.
Angles makes them shorter going in the other board and angled screws won't pull the board in tight. If you have a gap either the gap stays or you pull the board out of level.


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## jaketrades (Mar 2, 2017)

Nealtw; said:


> Set the laser somewhere and measure down from the light to the fixed area.
> Or just mark a stick at the line. lift the sister with the stick on top. When the light is at the line you are level. Nails are better .



Laser::: Smart! I like that. 

I understand that nails are better than say drywall screws, but better than deck screws? I’ve been using GRK #9 R4 fasteners to hold the sisters in place before I bolt them. The shear strength is listed at 876lbf.




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## jaketrades (Mar 2, 2017)

Couldn’t resist buying a palm nailer. Justified it with an almost expired coupon at HD. Plus screws cost more 











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## 3onthetree (Dec 7, 2018)

jaketrades said:


> Joist 2 - having the sisters spaced off Joist 2 to accommodate the twist is acceptable?


You've way over done it with the sandwiches, so with blocking between J1/J2/J3 I'd say you've got a lot of meat there for one bad beam. 



jaketrades said:


> Fasteners. - when you say min 3 high @12 OC - does that mean 3 fasteners in a vertical line every 12”
> 
> Nail gun - Don’t have a framing nailer. Would #9 3” deck screws suffice?
> 
> Toenail - do all of the fasteners go in at the same angle (20 degrees) or do you want to vary the angle?


My in-law engineers pulling/shear forces on nails for a nail gun manuf. I'm confident nails are as good or better than screws in rough framing. Besides, labor in time and our frail backs matter, and I'd prefer not to bolt unless required by spec in built-up beams. 
The minimum 3 vertical is a catch-all for a 2x6 or 2x8. Honestly wood is forgiving so if you vary the horiz spacing it's not a big deal in this situation. But I always toenail - compare pulling apart two boards straight-nailed vs. two that are toenailed at opposing angles.

Nice palm nailer for the tight spots, I'd think with 3 floors to go you wouldn't regret an $80 framing nailer to penetrate that old hard wood.


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## jaketrades (Mar 2, 2017)

I left J1/J2 alone for now because I need to move the steam pipe in the pic. Plus was looking at J2. She's really in bad shape. Looks like she's partially cracked in the notch.

And there's a vertical stud to the right of J1, so i won't be able to get that sister to sit on a bearing point.

A framing nailer would have been nice. I see Husky makes one for $88.


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## Nealtw (Jun 22, 2017)

It looks like the brick in the wall is just fill for J 2, I would remove some brick so the new joist could have solid support beside the old for at least 2" 
J 1 is even more important because the other beam is hanging from it. I would remove 2" of that stud so you could put the new in for solid support.


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## jaketrades (Mar 2, 2017)

I have a decommissioned fireplace that has a stainless steel chimney liner for a boiler inside of it. I'm going to make the space in front of the fireplace living space.

It's currently filled with rubbish and bricks. Will running one long beam across with joist hangers and blocking provide adequate support?

Thanks.


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