Joist meets Drain - now what?

Discussion in 'Shower & bathtub Forum & Blog' started by lhartl, Feb 5, 2007.

  1. lhartl

    lhartl New Member

    Hello,

    I am new to this forum.

    My husband and I are currently renovating our ensuite. We have removed the bathtub and are planning a large walk-in shower unit in it's place. We have purchased the 32 x 60 Schluter Shower System with an offset drain, hoping to utilize the current bathtub drain location (upgrading to a 2" pipe of course).

    Upon examining the existing plumbing, we can see that the bathtub drain was placed directly over a joist (notched to accommodate the drain fittings) - and upon examination of the Schluter drain system, we realize that we need to go almost 4 inches deeper with the new drain fittings.

    The 10" joist (on 16 inch centres) is currently notched about 3" and we will need to cut another 4 inches to build a 2" drain/trap to accept the Schluter drain. That would leave less than 3 inches of joist. The shower is on the outside wall, we estimate about 24 inches to the outside wall would be compromised.

    The offset drain in the Schluter foam tray is 10" from the edge, and to keep the slant from the edge to the outside of the drain, we have very little to play with.

    I am anxious to hear any and all ideas from the experts.

    Cheers,
    Linda
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,023
    Location:
    New England
    I think you'll need to cut that joist out and put in some headers on either side of it so you've got a reinforced box around the drain..
  3. Racer814

    Racer814 New Member

    Messages:
    124
    street 45 in the drain to angle out of the joist and then another to offset it back


    or cut and header the joists
  4. lhartl

    lhartl New Member

    Street 45 ?

    Thanks for the ideas, what exactly is a 'street 45' ? Can you explain a little more about these fittings suggested?

    thanks,
    Linda
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    A street fitting is male at one end and female at the other, and the suggestion here is that you first angle away from your joist rather than cutting it more. So, something like a couple of street 45s would let you dog-leg over a bit before going farther on down below the existing notch in your floor joist.
  6. lhartl

    lhartl New Member

    Picture for clarity

    Hi again, I am attaching a picture of the situation today. The circle that I drew on the board was from the shortest 90 degree elbow that I could find attached to the drain. This circle marks where the curve of that elbow would sit if the joist weren't there. As you can see, there is not much room from there to the main pipe and I need to get a trap in there and also a conversion from 2" to 1.5". I understand that I need to maintain a slope also.

    does this give you any other ideas? Should I just get a plumber in to look at this and make it right? I think I am over my head a little.

    thanks,
    Linda

    Attached Files:

  7. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,350
    Location:
    Yakima WA
    I would not use 2 45's that just makes the potential for a clog. The best thing to do is as Jim suggested. Cut the offending joist out and box around the area. This will return the support lost when cutting out the joint and provide the space needed.
  8. markts30

    markts30 Commercial Plumber

    Messages:
    630
    Location:
    Phoenix, AZ
    1st - you cannot place a 2" trap here and reduce it to 1-1/2" to fit into the existing tee....
    You have to replace the SanTee with a 2" tee and plumb it from there...
    Once this is done, you can figure out the best way to run your drain - in the long run the boxing out of the joists will be the best option...
    If you are not sure of what you are doing, take lots of pictures and make lots of drawings and, for the most part, we can talk you through the piping part - for the tiling, go to John Bridge's forum http://www.johnbridge.com/vbulletin/index.php? .
  9. lhartl

    lhartl New Member

    Cutting Back further

    thanks. Just to confirm, the San Tee is the pipe furthest away in the picture? I hear you say that I need to cut that one out and replace it with a 2" T, but there is no room to accomodate an even bigger pipe and 2 to 1:5 connectors or is there? I haven't seen them at HD but I will go back and look again if you tell me that I should be able to squeeze this in.

    I have new respect for plumbers! How do you work in such small spaces and keep your sense of humor? :)

    thanks,
    Linda
  10. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,350
    Location:
    Yakima WA
    Hello, what is it you are not understanding? Remove a section of the joist that is in way and box around the work area. Also, you can not reduce the size of the drain from 2" to 1-1/2". That would be an open invitation for clogs. You really don't have a serious problem here if you will just remove the joist.
  11. leejosepho

    leejosepho DIY scratch-pad engineer

    I will probably get shot for this, but it looks to me like that circle you have drawn is near the center of the joist, and if that project was my own, I would plate both sides or "make a sandwich out of" that joist to return it to its original strength (or at least very close), then drill the hole you need where you need it. And rather than trying to retrofit to 2", I would keep that bit of pipe (aws a nipple) already coming out of your tee and use it for connecting your new trap. But of course, neither was McGyver a plumber ...
  12. lhartl

    lhartl New Member

    Lee,

    Thanks for the suggestion. The Schluter shower drain is 2" and the old (existing) tub pipes are 1.5", so I must make the conversion somewhere in there. Mark has suggested that I swap out the current 1.5" SanTee and replace with a 2" SanTee - but this will require that I change the pipe connections coming in and going out of the SanTee. I can't possibly replace all the plumbing to 2", somewhere I have to end the 1.5" and I am up against another joist at that point.

    Do you think that I need to start at the SanTee with the 2" ?
    thanks,
    Linda:confused:
  13. Racer814

    Racer814 New Member

    Messages:
    124
    45'ing out of the joist ain't gonna cause a clog...lets be serious, it's not like we have solids going down here....I mean...I might not get out of the shower to go #1(don't tell my wife)....but I ain't going #2 in there.....:rolleyes:
  14. Racer814

    Racer814 New Member

    Messages:
    124
    you may not have enough room for 2 45's anyway...2 streets maybe, thats the easiest way if you have room....headering the joist on the 2nd floor aint no picnic , I would avoid it if possible...........the shower drain should be 2" by code....how hard would it be to change it? .....would it work going into a 1 1/2" drain...yes....is it a really good idea?.....no



    you would do yourself a favor by getting a proffesional in there...
  15. adrianmariano

    adrianmariano New Member

    Messages:
    79
    Location:
    Massachusetts
    What exactly do people mean when they say to build a box around the drain? I can't figure out how this would work without compromising the strength of the joist. I think the idea of bolting a sister joist in next to the existing one and then drilling out the hole in the center for the new drain is good for the structural integrity. The result will be stronger than what was there before.
  16. lhartl

    lhartl New Member

    The picture may be confusing everyone - the circle that I drew on the board shows where the drain and a short elbow WILL REST on the joist, it was a 'depth' indicator. So you see, the problem with sistering and drilling a hole won't work because I actually need that much depth in the board for this Schluter drain system and an elbow to get off the joist. I will attach a picture of the Schluter drain as fyi.

    Otherwise it would have been a great suggestion. I could still bolt a 2x4 (on end) across the length of the joist if I cut down to the 7" mark on this 2"x10" joist, then box it in from there - do you think that would be strong enough?

    We never had a problem with the 1 1/2" drain in the tub and we have showered there for 25 years, seems like the code is there for new installs maybe and setting some standards ?? Anyway, it doesn't matter now, we have this Schluter drain and it's 2". We must deal with it.

    thanks for the comments, it really helps to talk this thru. I have left messages for two plumbers in Coquitlam, no answers, I think everyone is too busy for such a small job. Any plumbers out there close to Coquitlam?

    another day....:)

    Linda

    Attached Files:

  17. adrianmariano

    adrianmariano New Member

    Messages:
    79
    Location:
    Massachusetts
    What kind of flooring is this joist going to be supporting? If it's tile or stone then you need to pay careful attention to your structure because if it's inadequate the floor can crack.

    Deflection of joists is inversely proportional to the cube of the joist height but only one times the width. A 10 inch joist has 7.5 times less deflection than a doubled 4 inch joist (your 2x4 sistered to the existing joist) so it is a LOT "weaker." (So the floor will sink 7.5 times farther when you step on it with your 4 inch wood in there when you step on it than it would with a 10 inch joist intact.) The floor will be weakened for the entire length of the joist back to wherever it is supported. (I got the above number by computing 10^3 / (2*4^3).)

    If you need to maintain the full strength then perhaps bolting steel plates to the joist is a solution. I did a quick estimate and this would appear to require approximately 1/2 inch thick quantity of steel if it's four inches high. If you want to go this route you should probably recheck my quick calculations, or maybe check with someone who really understands carpentry or structural engineering. (This is carpentry, not plumbing, by the way.)

    Now houses are overbuilt. You can probably cut that joist out entirely or execute some ineffective fix and as long as your flooring is flexible you won't have any serious problems. The floor might feel a soft and springy along the line supported by that joist. I had a joist in my house completely rot all the way through. It was the one at the edge under the wall. And yet nothing obvious had happened to the house as a result.
  18. I don't get it either

    Adrian is right. Every time I look at this thread, I wonder what I am missing, and I move on instead of re-reading carefully every word to see if I have missed something.

    Maybe we all need to see a large-scale photo. A joist, going from where to where, holding what up over how big a distance. That kind of thing.

    Adrianmarino, I'm glad you are here and contributing your knowledge. I also like the fact that you are I both use metal to build or reinforce structures.

    David
  19. lhartl

    lhartl New Member

    Hi again,

    I am attaching another picture of the area. The Schluter Shower System is 32 x 60 with a premade shower bed and drain kit. The drain in the premade bed is offset exactly the same place as a tub would be - 10 inches from the plumbed wall and centred at 16". I am planning to install porcelain tile over the walls and floor, so I am laying 1/2" backerboard over the new 5/8" plywood floor, using thinset of course. The Schluter polystyrene floor pan goes down next with more thinset and the entire floor and walls are covered with another layer of thinset and the membrane prior to the tiles. I expect this will be a very solid surface on which to tile. (This system is for the DIY'er but had I known that the drain would be such a problem, I may have opted for a custom mud bed and placed the drain where there is more room. I suspect that the Schluter drain is much larger than standard and this is another source of issues for me.)

    I can't imagine much standing weight over the drain and in the top ten inches of the 60" shower, but there will certainly be the weight of the tiles to consider.

    I am sorry this is so confusing, articulating this and using the plumber lingo doesn't come naturally.
    :rolleyes:
    Linda

    Attached Files:

  20. adrianmariano

    adrianmariano New Member

    Messages:
    79
    Location:
    Massachusetts
    I don't think she has pictures of the whole joist span. It looks like just that one little hole in the bathroom is opened up and there's a finished ceiling below. It should be possible to figure out what the joist span is, though, and obviously what it's holding up.

    Is using metal such a radical idea? My 50+ year old house has a metal I-beam down the middle. I can't say I've actually built with metal myself, but it's the only way I can see to get the strength to match a 10 inch joist in a 3 inch height.

    And actually I made a mistake in my calculations of the thickness required (in addition to using 4 inches instead of 3 inches which makes a big difference). Calculating again based on a 9.25" joist height, 1.5" joist thickness, and steel with E=30 vs douglas fir with E=1.6 (E is the modulus of elasticity that determines how the material bends) I'm looking to find the required steel thickness only 3 inches heigh that bends as much as a 9.25" high 1.5 inch thick joist made of douglas fir. I solve this equation:

    30*t*(3^3) = 1.6*1.5*(9.25^3)

    And get

    t = 2.34 inches thick

    That's a pretty serious amount of steel and probably impractical to handle. Maybe you can get 1.5" thick I-beams and bolt those to the joist? I don't know. Is there such a thing as a "half-I" beam where you have flanges only on one side? Then you could bolt one to each side of the joist.

    If you do or will have tile or stone flooring above this joist (anywhere on its length) you might try asking for advice on the johnbridge forum (previously mentioned) for advice on reinforcing your structure.
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