Joist Deflection, Subfloor, Porcelein Tile [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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03-07-2007, 03:07 PM
I have a lot of questions but after lurking in the forums a bit and using the Defloctolater I might not even have to ask them... (and not for good reasons).

We want to tile the kitchen. Currently there is vinyl, then hardwood/softwood, then ply, and then 1x5 planks. I'd get into measurements but I'd better start with something else first:

I don't think we can tile; please confirm or deny this.

I did the deflecto test and did very bad. Underneath the kitchen, the joists are a mix of 2x6's and 2x8's of unknown mid-quality wood (it looks old but not cracked). The joists are 14" long spanning the length of the kitchen and 16" OC.

I was originally going to talk about how the subfloor sags at one corner and that the deflection is around an inch at the corner. I was going to ask if I should put new ply down over the plank subfloor and use a self-leveling compound and feather that into the rest of the floor.

Do I need to even worry about those questions? Can we simply not tile? Is there anything we can do(what are all the feasible options)?

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03-07-2007, 03:32 PM
Bobo...wood looks great in a kitchen. It will flex with your floor, you can refinish it several times and you can still do it yourself. I wouldn't do a laminate unless your going to glue it to the floor or glue the edges. Personally...I like using a nail gun better. Randy.

03-07-2007, 03:36 PM
Thanks for the response but maybe we didn't communicate correctly =)

There will be no wood in the kitchen (finished). We will be removing the douglas fir and using it for the rest of the house where we will be refinishing the wood.

My question is if there is any feasible way to tile or should I just do a new laminate.

03-07-2007, 04:08 PM
If you did the Deflecto and failed, the only way you can help yourself is to go below and support the kitchen floor structure until it passes.. Shorten the 14' span..

How are your floor joists arranged such that you have 2x6's and 2x8's over the 14'? Can ya take a pic from below? Can you support from below?

03-07-2007, 04:58 PM

There looks to be a 2x4 between the joist and the beam where the 2x6's are used.

The 14' joists are continuous but are resting on a beam/wall that rest perpendicular to the half-way points of the joists. Because this takes the load off the joists, can I consider the joists as 7' joists within the deflectolator?

I can take a pick from below, where is it proper to post it? Should I host it at an imageshack and point a url there or is there a place to host pictures within this forum?

03-07-2007, 05:33 PM
I think my point was too subtle. You have a poor joist system. Unless you want to start over, you may want to go with something other than tile. I know thats blasphemy around here, but...

To get to what you need you would porbable have to add two more headers from below ay 1/4 and 3/4 points of the floor. Now you have to level it. Then you have to worry if your joists themselves are going to fail. 2x6's and 2x8's!!! in the same joist system smacks of poor workmanship, which suggests shotty products.

If you want to use laminate you will have to get a level floor but the amount of flex still worries me. Also, you should glue the edges since the is some water exposure in a kitchen.

Solid wood can be used on less than desirable subfloors. I have rehabed many a rental property on a boucy floor, as long as it won't through. Don't shoot the messenger!!! Randy.

03-07-2007, 05:42 PM
Bobo...just thought of something. I redid an 1900's shotgun in Mississippi and they had enclosed a porch to add to a kitchen. That may explain your 2x6's and 2x8's. A liitle more info about the house, floor and pics may help. Randy.

03-07-2007, 06:28 PM
Thans wannaBpro; I took your subtlety but in vain... I didn't want to hear it =)

I might just have to do hardwood in the kitchen... doesn't excite me though because I'd have to buy a lot more Bona Traffic and that stuff is not cheap.

I will be taking pictures soon.

The house, oh the house:

1920's house with very poor workmanship all around. Was originally small but is quite big now with recent (20 years ago) add-on of a great room and finished basement. The people that did the add-on were extreme but poor DIY (the guy actually does construction in the area and I would NEVER hire him). The entire house reeks of half-baked ideas and attempts that I won't even go into.

Most of the joists have already been previously sistered. I'll take quite a few pictures and post them later tonight.

Oh, and the other thing; the rest of the house is douglas fir which we will be taking up, planing, and refinishing. On reason I don't want hardwood in the kitchen is because I can't find douglas fir around here... only oak (within my price range) and I don't want it too look off surrounded by douglas fir.

03-07-2007, 06:33 PM
What does that wall at the 7' mark look like? A regular wall, or a wall with the top support members on their sides?

If thats not the case we may need a structural member to respond here..

Get it, a Structural Member..... :stick:

03-07-2007, 06:43 PM
The wall has a support beam running parallel and on top of it. It looks to be a thick rectangular log. I'll take a picture of that too. I'm not exactly sure what you mean by top support members on the sides. I'll take pictures all around it. I have the majority of pictures finished already but my brother-in-law has me usb-to-memcard reader and I can't get a hold of him, though he is supposed to stop by tonight.

03-07-2007, 08:08 PM
If Im understanding this correctly you have a 14foot wide kitchen.

Under that kitchen you have 2x6 joists that are 14 feet long

those joists are supported at the ends

at the 7 foot mark, those joists you have a wall with a beam on top.

With that information your deflection is 500+ good for ceramic- assuming the floor structure is in good shape.

The wall at the 7 foot mark reduces the span. The number to input into the deflecto is the unsupported span face to face, not the length of the joist. That wall with a beam on top supports the floor- not all walls are load bearing, but the fact that there's a beam on top is the key. You will have to deal with subfloor problems like you suspected, and if you have some you probably have others. Pictures will tell the story. The wall construction/beam support is an area to look at given the history of the previous owner and the age of the property.

03-07-2007, 09:08 PM
SteveB, that is exactly correct.

Here are the pictures (hosted at Flickr):

If you want me to take different pictures of different aspects or at different angles let me know.

03-07-2007, 10:55 PM
What does the bottom of the wall look like? What does it sit on? It looks like it runs down to some basement floor(nice paneling :tup1: )- what is condition?

If its got a decent bearing the beam and studs are more than adequate for support- looks to me to be a 4x8 beam with supports every 16 -24 inches inches , cant get much better than that.

The beam ends, but does the kitchen floor continue? That implies that the beam is not continuous across the whole kitchen whcih would need to be addressed. Got a pic looking along the beam to its end and beyond?

The sisters in some of the later photos - more details on those- length?, where in the span are they? What is the condition of the original joist, any obvious reasons they were installed? Some old houses just have the joists scabbed together here and there.

The sisters need more inspection- probably more fasteners - hard to see any in the pic but I would like to see them 16" or so on center, two rows, thickness of member away from edge.
Looks to be some nice looking old growth douglas fir- dry too I bet.

Is the floor fairly flat- not level, but flat across the room- stretch some stings if needed. Looking for dips at supports.

Floor has a few layers - you are removing which one to use elsewhere? What will be left? You dont like the wood grained vinyl? on top of the DF????

Hard to tell but the members look to be OK, connections should be checked, I would also look hard at the sill connections. The addition area is suspect. Old houses frequently have moisture and or termite problems in my area too.

03-08-2007, 07:20 AM
Thanks for the detailed post.

I'll try to take some more pictures in a bit but since I MAY be able to tile I'll get to my other original questions that will address some of your previous questions, like is the floor flat. Oh, and my wife does not like the vinyl so that's why it's coming out (it has gouges here and there too - it seems to be that soft flex-vinyl). So the vinyl will be coming out and the douglas fir will be planed and reused in other parts of the house where we will be keeping douglas fir. That leaves just the planks and the ply on top of those planks left.

The floor is basically a parabola... 1" deflection in one spot and only 1/4" in another. The room bows down to one corner.

My ideas are (and please comment on whats best and what's even feasible):

1) Shim the low spots between the joists and subfloor with actual shims or custom made Xx2's.

2) Use self-leveling compound to level this sunken corner and feather it out to the existing floor.

3) Give up tiling and put down some oak flooring.

If we choose to go route (2) should we remove the existing subfloor+ply and put in a 1-1/4" double layered exterior grade ply or should we remove the old ply and put fresh 1/2" ply over the existing subfloor (this way we could put down #30 saturated felt over the planks, put down some self-leveling compound, and then put on the ply). Looking from underneath via a drop-out ceiling the subfloor looks to be a combination of 1/2 5x1 planks and 1/2 3-1/4" tounge and groove. We'll be ripping out the existing vinyl flooring today at 2pm CST and I'll know a little more after that.

The beam stops at the end of the kitchen so the beam does go throughout the kitchen.

03-08-2007, 07:33 AM
Bobo...look up Lumber Liquidator and other discount flooring dealers on the can find good deals on other types of flooring. Check Ebay too. Do you have any discount building suppliers in your area? If you can run a sander...look for tavern grade flooring, its cheaper but needs a little more work. New tavern grade in an old house looks like its been there forever. I think SteveVB is assuming good quality joists but I wouldn't count on it. Good luck and keep us posted. Randy.

03-08-2007, 07:39 AM
Bobo, just reviewed your pics. Some of the beams look good...some ok. It looks like they don't all sit on the support below...try to put shims on top of the beam to reach the joist. It will hold your floor up, IMO tile isn't a good idea. Randy.

03-08-2007, 09:11 AM
Here are some more pics, don't know if I improved upon anything:

Underneath the kitchen is the laundry room where you see the beautiful paneling and the other half (separated by the wall/beam) is a non accessible "room" filled with dirt. I have no idea how far down the exterior wall goes that you will see in one of the pictures. I'm shooting these pictures through a jaged 1' diameter hole in a cement wall so I can't do much better.

I saw no obvious reason for the sistering... the sistering looks of poor quality as some jobs are not flush and they are all connected with seemingly haphazardly placed nails. I can tell that the sistering starts about 2' away from one end of the 14' span, crosses the beam, but from there I do no know how far it goes as I'd then be in that non accessible room.

I really can't get close enough to look at the sill connections; I'd try harder but I can't find my flashlight ANYWHERE... my daughter was playing with it last night so it's on some odd end of the house but I searched to no avail.

Let's just say I don't tile and I buy some hardwood... non-aesthetically but structurally should I still flatten the floor or does it not matter near as much for hardwood? Also, can anyone identify the layer between the plank subfloor and the douglas fir... is it particle board or OSB as it really dosn't look like ply. If it's not ply I'll take that up and put down ply.

03-08-2007, 11:20 AM
Hi Bobo. That is quite an archaeological dig you have going on here. ;)

Re. that second layer of the floor sandwich, it's hard to tell from the photo what that might be. However, given the probable age of that next ship-lap layer I'm thinking that middle one might even be another layer of boards set in the opposite direction.

Whatever the case, minus the vinyl and it's 1/4" underlayment, you have three layers of flooring down now and whichever way you go you are about to add some more. If you proceed with tile you will be adding three more (ply + backerboard/CBU or membrane + tile). Me thinks it time to consolidate. I'd seriously consider removing everything down to that first layer of T&G boards. Then add a new layer of 1/2" ply minimum.


03-08-2007, 04:10 PM
I don't know if anyone can answer this (as it IS a tile forum) but:

Let's just say I don't tile and I buy some hardwood (which I am highly anticipating is going to happen)... non-aesthetically but structurally should I still flatten the floor or does it not matter near as much for hardwood?

If I do flatten it, I'd probably take it down to the planks. Then put down some #30 saturated felt. Then I'd use self-leveling compound to level it and on top of that put down some 1/2" or 3/4" double sided exterior ply. Would this be good to do - any kind of special nails/screws I should use for going through self-leveling mortar so that the integrity of the fasteners stay intact.

How about this second scenario, I leave down that unidentifiable middle layer above the planks. Could I apply self-leveling compound above this, then red rosin paper, and then lay the wood right over the self-leveling compound and red rosin paper?

03-08-2007, 04:29 PM
Bobo...Mikes point is well taken. But it looks to me like you have 1/2" plywood, 1/4" hardboard (not structural and totally unnecessary) then 3/4" wood flooring. I would rip off the flooring and hardboard and lay down 3/4 plywood. Finish the floor from there.

Now...leveling the entire floor is a cunumdrum. If you use 3/4" T&G could get away with not leveling it. Sometimes the enemy of good is better. Old houses require some tradeoffs and if your not going to start the best you can with that floor. Trying to level it without redoing the joists will require shims made of 2x4's and can be a very tricky process cutting them right. You may wind up more problems. Self Leveling Compound will work...but you will need a lot of it and it can get expensive.

Since I'm a half bubble off plum...i would live with the floor and tell everyone my house has "character".

03-09-2007, 07:14 AM
couple things-

that dirt under the floor needs to be addressed- you should get it cleaned up and a vapor barrier put down. The moisture drive from the soil up into the floor system is going to cause problems for any floor thats installed- a wood floor is going to experience gaps and more seasonal moisture movement than you want. I wouldnt use rosin paper, felt to reduce the moisture swings.

any dip and or out of plane area is usually a sign of a problem, ignoring them and spending money to cover them up has never been a good idea in my view. If you were selling the house and wanted to pass them on thats one thing, but if you are going to live there for any length of time the effort expended will most likely make the home a bit more enjoyable. I dont like character- squeeks and creeks drive me nuts, but thats me.

I think no matter what the finish is going to be I would strip it down to the T&G subfloor planks, make my repairs to the structure as needed and then run 3/4 ply over top, ditra/cbu and tile.
The other idea would be to remove it all- for easier access to the the dirt floor, since I gather that access to that area is limited. Excavate the dirt so you have a minimum of 18" between the wood members and the dirt. Install the vapor barrier on the dirt. Repair the floor system. Insulate, lay down new 3/4 T&G ply, ditra/cbu , and tile.

03-09-2007, 08:08 PM
Thanks everybody for your responses; I really appreciate all of them.

We just took up the floor in the nursery, our bedroom is tomorrow, and the kitchen likely over the weekend/early next week. I might have more questions then but we will be taking the floor all the way down to the existing plank subfloor and will be putting down new ply and likely hardwood.

Does anyone know if there is an equivalent forum like this but for hardwood flooring where I'd get good concrete answers or is it OK if I muddy up this thread with question regarding the subfloor for laying hardwood (we know how to lay hardwood, it'll likely only be subfloor questions).

03-09-2007, 08:17 PM
Bobo...continue here. I think we can talk you through it. If you get to your dirt floor, put some poly down on it. Randy.

03-09-2007, 08:27 PM
Thanks, you all are very helpful and this definitely is the friendliest DIY forum (in a very good way) on the web.

I have an alternate question regarding the subfloor in the nursery (where we just took up the hardwood and are down to the subfloor planks):

In the nursery there is a large deflection along a wall. It's about a 5/8" deflection over 36" and runs parallel to the entire wall; it angles down towards the wall. The door to the room is also within this wall. On the other side of the door is more subfloor in entryway that connects two bedrooms where we will be refinishing douglas fir and this too deflects down to the door. So basically I need to level the flooring 36" from both sides of the door and also along the 16" wall in the nursery. Would it be better to remove the tongue and groove subfloor, shim the joists, and refit the tongue and groove subfloor (or put down new ply) or would it be better to put some #30 saturated felt down over the existing subfloor and use some self-leveling compound? I know it would be much more expensive to do the latter but I want to know what is best and most feasible.

As a latter thought, if I did shim it would it be better to sister the joist instead of shimming it and raise the sistered 2x6 up the amount needed?

05-06-2007, 02:35 PM
Just to let everyone know everything worked out well!

We got the subfloor pretty darn level and decided to put hardwood down instead of tile; we stained the kitchen and kept the rest natural then put down some Bonakemi Traffic and it looks great!

Unfortunately I have a new problem, but I know with all your help I'll get it figured out real quick... but I'll put that in a new thread.

Thanks for your help everyone, it was really appreciated!