# plank and beam 1956



## trickle (Oct 27, 2015)

Have a 1956 fixer home. Posts on footings every 4'-6" each direction. 
4"x6" wood beams 4'-6" OC. 2x8 (non-t&g) planking over beams (1/8" gaps), with 1/2" plyw subfloor over planks.

Is this a ceramic tile stable floor system? No noticeable bounce, but there is obviously some flex, and backerboard would not change that. Adding posts in crawl space would stiffen it, but is it needed? This is 1-7/8" of combined wood deck/subfloor supported at 4'-6" each (NS-EW) direction. 

Backboard, if it would help, causes that raised floor height issue that becomes a problem in many areas.

Thanks in advance for the advice or direction.

Originally from Wisconsin. Wife is from California. This is a San Diego old build like I had not run into in the Midwest. Not many young folks even know what I am talking about.


----------



## Fouthgeneration (Jan 7, 2014)

Install a 2x4 or 4x4 under the existing 4x6 beams add joist hangers to the beams and install some 4' long 2x 8s or 2x 10s to stiffen up the floor.


It would far cheaper just to remove the existing floor, fix the framing and replace recycled material or new sub flooring.:thumbsup:

Add radiant floor heat while your are fixing the old girl. don't forget the vapour barrier.


----------



## CarpenterSFO (Dec 12, 2012)

trickle said:


> .... This is 1-7/8" of combined wood deck/subfloor supported at 4'-6" each (NS-EW) direction. ....
> .....


Sort of... if I've visualizing it correctly, you have long bays between the 4x6 beams. Is that correct?


----------



## fjn (Aug 17, 2011)

Your question is simple enough,unfortunately,the answer is much more complicated. One variable that has a big impact is tile size.Mosaic is quite forgiving, 20" x 20",not so much. 

I would suggest research articles by Mike Bryne.He has written many articles in JLC and FineHome Building. Also get a hold of the tile bible (the blue book) it is written by the tile assoc. I believe their HQ,s, are in DC.


----------



## fjn (Aug 17, 2011)

http://www.tile-assn.com/?page=refmanual



This is the book I referenced,the cover is not blue anymore though.:laughing:


----------



## trickle (Oct 27, 2015)

yes correct. A 4x6 beam supported at 4'-6". Beams are also at 4'-6" OC to each other, so there are 4'-6" x 4'-6" bays with 1 7/8 inch of combined 1-1/2" thick solid wood "decking" (the 2x8's), and then the 1/2" plywood sub over that. It is way more stiff than my other house with 2 x10 joist at 16" OC and conventionally built and with rock board over that where tile is installed. There, the whole room would flex/bounce between exterior masonry foundation wall and center house beam.


----------



## trickle (Oct 27, 2015)

12 x12 ceramic tile. This system is really pretty darn stiff.


----------



## trickle (Oct 27, 2015)

Thanks! As much as I love load calc tables, etc (not), I'd better check it out.


----------



## CarpenterSFO (Dec 12, 2012)

If it's all sound, I'd probably hang a 2x8 joist across the middle of each bay.


----------



## trickle (Oct 27, 2015)

Thanks 4th Gen.

Yah, I know the hard/right way too, and it may come to that. But, when it comes to working in a crawl, it is tempting to just blow it up and start all over. The HVAC guy ran his ducts all around the perimeter and in between. Can't get over or under them. And the head knocking cast iron sanitary piping is hanging all over the place too.


----------



## trickle (Oct 27, 2015)

Bob, 

Adding a 2x8 across each bay:

That was my thought too, if no one mercifully waved their magic wand and made the headache less painful. Cutting the span in half would make the floor extremely solid, in my scenario. Wherever there is a partition, an additional beam is present, so some beams are maybe 3 feet apart. Those areas are noticeably more stiff. They won't even noticeably move when I jump on them.


----------



## trickle (Oct 27, 2015)

Correction: 

Per the original 1956 blueprints, the subfloor spanning over the 4x6 wood beams is constructed using 2x10's laid flat with 1/2" plywood over that. Max span 4'-6", most areas approx. 4 feet.


----------



## hdavis (Feb 14, 2012)

If it was T&G, I don't think you'd have to do anything more.


----------



## Fouthgeneration (Jan 7, 2014)

Remember with your intermediate supports your existing floor will actually "pop' up in un loaded bays if the 2" x 10" plank span 3 or more beams.


Removing the sub floor is the smart way to a tile ready base, consider using 1.25" t & g subfloor to allow 19.2" or even 18" joist spacing instead of 16 or 12" for ease and speed of up grade. Room for the old and fat to work.

Ask the lumber yard if they can secure a lift of 9' or 10' long flooring T&G to further reduce waste and laborious blocking.

You might want to investigate some seismic up grades on the pier connections.


----------



## trickle (Oct 27, 2015)

4th gen,

Thanks! If you mean the lever effect of a multi-bay spanning 2x10 floor plank lifting an adjacent bay floor plank, yes, I thought about that too. You can imagine, being a 1956 build, how long these planks might be (when real trees still stood tall. Every header is a solid slab including over the 18ft garage door). I don’t know how much deflection we are talking about with a ½” plywood underlayment screwed to a 2x10. I mean, wood moves, no matter how you assemble it, so there will always be deflection. I don’t know if there is a practical method then to remove the inherent risk of tile over wood. FYI: a pan of water over the beam won't dance no matter how hard you jump. Between beams: Yah. Some. You would never break a 12x12 tile, but you'd be working the mortar bond if you bounced on it between beams. 

The reality is that this is a one story 2400 sf, rafter (not trussed) roofed house with rafter bottom cord spices, raised and drop ceilings, lots of bearing partitions with built in cabinetry (dressers, desks, linen cabinetry, pantries, etc –all custom built in) that can’t be practically removed, to replace the core wood structural foundation. The house shape actually faces three directions, starting out EW then bends 28 degrees, and then turns another 55 degrees. Enough bearing walls issues to make you dizzy when you look up in the attic. IE: the partition must stay in place.

Sooo, if you start removing/replacing anything structural below the floor, you end up not spanning to the next beam for support in every room, as the perimeter beam (to attach to) in every room is directly under the room partition. The practical choices left are ones that stiffen up what is here.

This is one of those where, clearly, you could tear it down and rebuilt it faster than renovating it, if you can’t come up with some unique ideas. I am living in it, so I have got time, unless my wife divorces me first. I have near used up her good will, so I need to literally let the dust settle from time to time.

For better or for worse, I do appreciate all the input. This is exactly what I need. Great to have you all chime in with your thoughts.


----------



## Fouthgeneration (Jan 7, 2014)

Underpin: Install a basement under where You want the tile, then fix the framing. Room for decades of stuff to pile up....:jester:

Find a house with tile ready flooring. Move. Or build a copy with sound framing and sell the practice house....:thumbsup:

Even digging out crawl spaces to 4 or 5 feet deep if possible would speed any upgrades, think young and dumb with conveyors, tell them you're importing herbs and powders....


----------



## trickle (Oct 27, 2015)

4th gen,

Good Lord, man! You think like I do. I like it, but it's also real scary, because I am tempted to actually do one of those things!


----------



## Fouthgeneration (Jan 7, 2014)

"Life is short, when you're dead, you are dead a long time." M.D. Anderson.

We can make more money, but we can't make more time....

Don't let the pursuit of perfection stop the enjoyment/use of the Good.

Buy some nice rugs or carpet and drive on to a real problem, tile the Patio/porch slabs instead?


----------



## trickle (Oct 27, 2015)

Yup. My wife is way ahead of you. She has everything covered with nice rugs.
For myself, I could go over to the neighbors and tile his kitchen. It’s on concrete.


----------



## CarpenterSFO (Dec 12, 2012)

The serif font is freaking me out.


----------



## Golden view (Feb 16, 2012)

How is the ply attached? Can you remove and glue new ply extremely well to bridge the planks as T&G planks would? First, do a deflection test.


----------



## trickle (Oct 27, 2015)

Thanks trowelhands. The plywood is nailed and as expected is not as tight as it once was 57 years ago. Over the beams you can jump and the water in a cup won't move. The 4'-6" space between the beams, the water will jump straight up and back down, so even though it's rigid, the span has deflection. 

Just screwing down the old plywood would help, but, you bet, gluing and screwing new stuff would go further in helping to stiffen the deck up. Not sure how much is enough. I mean, I have calmed down quite a bit through age, so I don't jump up and down too much anymore, ....except to see what damage I can cause to the floor.


----------



## Golden view (Feb 16, 2012)

Might try an actual deflection test with a straightedge and bags of thinset. L/360 over 4' is about 1/8". Keep in mind 3/4" subfloor at 16" OC doesn't deflect to L/360 until there's something like 250 or maybe even 500 pounds per square foot.


----------



## hdavis (Feb 14, 2012)

Since the boards aren't T&G, the only part of the floor acting as a diaphram is the 1/2" subfloor. You can improve that by screwing and gluing plywood to the underside of the boards. Alternatively, you could run a 2X on the flat down the middle of the bays (if you can get them in).


----------



## GO Remodeling (Apr 5, 2005)

hdavis said:


> Since the boards aren't T&G, the only part of the floor acting as a diaphram is the 1/2" subfloor. You can improve that by screwing and gluing plywood to the underside of the boards. Alternatively, you could run a 2X on the flat down the middle of the bays (if you can get them in).


If you add a 2x forming a "L" shape onto the flat 2x mentioned, you have a little beam which improves the strength.


----------



## hdavis (Feb 14, 2012)

olzo55 said:


> If you add a 2x forming a "L" shape onto the flat 2x mentioned, you have a little beam which improves the strength.



He says he doesn't have much room underneath, so I was giving something that may be doable under the circumstances. Golden View had the same general idea, plus doing his suggested evaluation could save unneeded work.


----------



## trickle (Oct 27, 2015)

Golden,

*Floor Deflection Test:*



*Two tests. One with weight stacked center of bay between the beams, and a second test with weight over the beams (which themselves are supported with a pier at 4’-6” intervals). The results are as follows:*



*L=54” The distance between the 4x6 beams, and also the same distance between the beam support posts. Probably old code or guidelines?*



*54/360=.15, or approx 5/32*





*Bay #1 *



*Load: 200 lb*

*deflection w/load between beams: approx 2/64, or .031*

*deflection w/load over beams: none measurable*



*Load: 355 lb*

*deflection w/load between beams: approx 3/64, or .047*

*deflection w/load over beams: less than a sheet of paper*



*Load: 409 lb*

*deflection w/load between beams: approx 4/64, or .063*

*deflection w/load over beams: less than a sheet of paper*







*Bays #2 & #3*



*Load: 200 lb*



*deflection w/load between beams: less than a sheet of paper*

*deflection w/load over beams: less than a sheet of paper*



*Load: 355 lb*



*deflection w/load between beams: 2 sheets of paper*

*deflection w/load over beams: less than a sheet of paper*



*Load: 409 lb*



*deflection w/load between beams: 3 sheets of paper*

*deflection w/load over beams: less than a sheet of paper*





** typical sheet of paper is .004*



*I am guessing that screwing the plywood down will probably clear most deflection at 200 lb. and somewhat at 300 lb. Don't know about 409 lb.*



*Thought?*


----------



## Golden view (Feb 16, 2012)

Sounds pretty good to me. Put Kerdi over it if you can handle another 1/8" height and it'll probably be fine. For what it's worth I did a floor with almost the exact same design earlier this year.


----------



## trickle (Oct 27, 2015)

*Golden,*



*Thanks. Good to be over that hurdle then. By that I mean “This Old House” hasn’t got anything on this old house and its outside the box methods and materials. One head scratcher after another. Nothing conventional or modular. All built in place and lots of angles. The archit/designer of this home passed about four months ago. It’s very possible that an owner of one of the homes he designed found him and took him out, otherwise he certainly died laughing.*



*You are suggesting to install the Schluter’s Kerdi shower vapor/waterproofing barrier and not the Schluter’s Ditra honeycomb tile underlayment right? *


----------



## Fouthgeneration (Jan 7, 2014)

If you must try tile with out "fixing" the floor system, install a 4'6" x 4' 6'' test panel that passes over a beam and extends to all the possibilities. Let it cure a week or month, invite the kids or grandkids to break it like the Samsonite luggage handlers.
Send me 10 % of the money you save next year.....

Tell momma you are not sure about the color.

Ask an local 30 year + tile installer if he'd bet his life on your floor not cracking, not the salesman. the actual mechanic.


----------



## trickle (Oct 27, 2015)

*4th gen,*



*Yup! That’s was always the plan. Anytime I step outside my field of expertise, it’s a test, with an exit strategy.*



*I’d like to do bathrooms, laundry room, and kitchen. All are small floor areas.*



*This first tile “test” will be in the laundry room only, and it is iffy enough that it was intended to be a test. It either will or won’t work in a hurry. Whether it’s kid proof, I wouldn’t dare say. Is anything? The tile will never crack from any dead load, or “normal” use, though. I am sure of that. We’ll see what we’ll see. I’ll keep the check book handy though. 10% ? That’s highway robbery! I won’t go over 5.*



*To be clear, I’m with you, if it weren’t for the cast iron sanitary lines and gas lines and water piping and ductwork, etc, in the way, in the crawl space, I’d beef things up below just to know I’m covered for all possibilities. It just is not possible with all the interference. I literally had to dig a trench to get in there under all the trade work to take a look. Whatever is done, has to be done on top, or tile is not an option. If not an option, then maybe a fast and crappy floating engineered floor and be done with it. The grand kids will destroy that in a week. That, I am sure of. Man….I do hate those floors.*



*I think the designer knew what he designed, in 1956, when he spec’d indoor outdoor carpet in the bathrooms, kitchen, and laundry room, and spec’d regular carpet everywhere else. He sidestepped the issue of floor covering altogether. Something about carpet in wet areas seems so wrong, even though it held up for 57 years now.*


----------



## Golden view (Feb 16, 2012)

trickle said:


> *Golden,*
> 
> 
> 
> ...


Oops, I mean ditra.


----------



## Sfnativepaul (Jul 9, 2020)

trickle said:


> Have a 1956 fixer home. Posts on footings every 4'-6" each direction.
> 4"x6" wood beams 4'-6" OC. 2x8 (non-t&g) planking over beams (1/8" gaps), with 1/2" plyw subfloor over planks.
> 
> Is this a ceramic tile stable floor system? No noticeable bounce, but there is obviously some flex, and backerboard would not change that. Adding posts in crawl space would stiffen it, but is it needed? This is 1-7/8" of combined wood deck/subfloor supported at 4'-6" each (NS-EW) direction.
> ...


Midspan support? Or sturdy floor 3/4 inch plywood is about 2 times the cost but much more Ridgid


----------



## Sfnativepaul (Jul 9, 2020)

CarpenterSFO said:


> The serif font is freaking me out.


Then use schluder tile decoupler/underlayment/moisture barrier


----------



## avenge (Sep 25, 2008)

Sfnativepaul said:


> Midspan support? Or sturdy floor 3/4 inch plywood is about 2 times the cost but much more Ridgid





Sfnativepaul said:


> Then use schluder tile decoupler/underlayment/moisture barrier


You're 7 years late.


----------

