# Mobile home floor sag beam size?



## UlyssesSign (Feb 27, 2018)

Hello all. 
I have a mobile home that has been put on a foundation, the floor joists are 2x8 and cannot take the weight of the 14' span of the house. They are sagging considerably, I've noticed some interior walls pulling away from the ceiling by about 1/2"

I have a 5' crawlspace and plan on installing a beam under the house to take the weight. 
The span of the floor is 14'. 
2x8 floor joists. 
I am wondering what size lumber I can get away with for the beam
I live in Canada so a 16' 2x10 is 30$. Just for reference. 

Thanks guys.


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## Sparky617 (Feb 27, 2018)

Was the steel trailer frame removed when you put it on a foundation? 2x8 is really undersized for a 14' span.  You're going to need a beam with several posts down the middle of the floor.  I'm not an engineer and don't play one on TV, but I suspect a glue-lam or 3 2x10's glued and bolted together with a pier or steel post down to a footing every 8 feet.


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## nealtw (Feb 27, 2018)

Sparky617 said:


> Was the steel trailer frame removed when you put it on a foundation? 2x8 is really undersized for a 14' span. You're going to need a beam with several posts down the middle of the floor. I'm not an engineer and don't play one on TV, but I suspect a glue-lam or 3 2x10's glued and bolted together with a pier or steel post down to a footing every 8 feet.


 A little over kill, 3 3" nails 16 inch on center, there are no forces pulling them apart.
 If you can get down to the footing  on the end a treated 6x6 would sit right on that. The pad in the middle would be about 24 x24" can be just dug down, no forms needed with a 3 x3 grid of 5/8 rebar keep the rebar well within the concrete.


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## UlyssesSign (Feb 27, 2018)

unfortunately the frame was removed and discarded.
2x10's was my first plan but i was hoping to get away with 2x8's just for cost sakes, but im thinking that i will just end up saving the costs in less support jacks.
8' span would be the best even with a glue lam beam you think? 
thanks,


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## UlyssesSign (Feb 27, 2018)

the guy that did the work left a TON of cinder blocks under the house, so my plan was the just build up two end pillars to hold the beam and then jack posts for everything in between.


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## Sparky617 (Feb 27, 2018)

nealtw said:


> A little over kill, 3 3" nails 16 inch on center, there are no forces pulling them apart.
> If you can get down to the footing  on the end a treated 6x6 would sit right on that. The pad in the middle would be about 24 x24" can be just dug down, no forms needed with a 3 x3 grid of 5/8 rebar keep the rebar well within the concrete.




I'm not following your design there.  Are you talking about a nailing pattern for the beam?     Clearly, the 2x8's were designed to sit on the steel tow frame of the trailer, without that in place something structural is going to have to be added to handle the load of the floor and any load bearing walls in the trailer.


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## UlyssesSign (Feb 27, 2018)

Sparky617 said:


> I'm not following your design there.  Are you talking about a nailing pattern for the beam?     Clearly, the 2x8's were designed to sit on the steel tow frame of the trailer, without that in place something structural is going to have to be added to handle the load of the floor and any load bearing walls in the trailer.



I was a little confused as well.


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## nealtw (Feb 27, 2018)

Seldom has an engineer ever asked for more than 3 nails 16" on center and never glue for laminating timber into a beam'
As suggested 3 ply but the span for that is too much, so a center post is needed too. posts are 6x6
The confusing part is??


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## Sparky617 (Feb 27, 2018)

My beam would run lengthwise on the structure, with posts every 8'.  That would reduce the span of the 2x8's to 7 feet.  Are you saying that span is too much and it would take two beams running lengthwise?  

Bolting it together may be over-kill.  See my comment about my engineering credentials or lack thereof.


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## nealtw (Feb 27, 2018)

Sparky617 said:


> My beam would run lengthwise on the structure, with posts every 8'. That would reduce the span of the 2x8's to 7 feet. Are you saying that span is too much and it would take two beams running lengthwise?
> 
> Bolting it together may be over-kill. See my comment about my engineering credentials or lack thereof.


My beam runs just like yours, up the middle, the ends can be posted down to the footing, I said center post but I agree with your 8 ft between posts:thbup:


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## Snoonyb (Feb 27, 2018)

This might help; ALLOWABLE SPANS FOR DF #2 FLOOR GIRDERS SUPPORTING ONE FLOOR ONLY
Max. Floor Dead Load: 15 psf 1, 2 (T-R602.7(2))
SIZE
                20-ft Building Width        28-ft Building Width           36-ft Building Width
2-2x6-             4&#8217;- 6&#8221;-                             3&#8217;- 11&#8221;-                              3&#8217;- 6&#8221;
2-2x8             5&#8217;- 9&#8221;                             5&#8217;- 0&#8221;                                4&#8217;- 5"
2-2x10           7&#8217;- 0&#8221;                             6&#8217;- 1&#8221;                                5&#8217;- 5&#8221;
2-2x12           8&#8217;- 1&#8221;                             7&#8217;- 0&#8221;                                6&#8217;- 3&#8221;
3-2x8             7&#8217;- 2&#8221;                             6&#8217;- 3&#8221;                                5&#8217;- 7&#8221;
3-2x10           8&#8217;- 9&#8221;                             7&#8217;- 7&#8221;                                6&#8217;-9&#8221;
3-2x12         10&#8217;- 2&#8221;                             8&#8217;-10&#8221;                               7-10&#8221;

Transform the "width", in this case to "length".


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## K_M (Feb 27, 2018)

Snoonyb said:


> This might help; ALLOWABLE SPANS FOR DF #2 FLOOR GIRDERS SUPPORTING ONE FLOOR ONLY
> Max. Floor Dead Load: 15 psf 1, 2 (T-R602.7(2))
> SIZE
> 20-ft Building Width 28-ft Building Width 36-ft Building Width
> ...


 
and keep in mind that this is for girders (beams).

Floor joists can span much more than this.

Current building code prescriptively calls out max span for 2x8 joists:
Doug fir/larch #1 = 12'- 4"
Hem Fir #1     =     11'-10"

a 14' span *should* be a 2x10.

Also, I believe a mobile home with a removable frame is actually called a "modular home" and is designed to have the transporting structure removed once it is placed on site.


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## Sparky617 (Feb 27, 2018)

Not sure this is a modular or a mobile home. The OP called it a mobile home.  Most modular homes are minimally a double-wide unit and not a single 14' wide unit.  

Regardless, 2x8's are too small for the floor joist without a beam.  Single wide units aren't designed to be removed from the steel trailer base.  His sag issues are showing that to be the case.


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## UlyssesSign (Feb 28, 2018)

nealtw said:


> Seldom has an engineer ever asked for more than 3 nails 16" on center and never glue for laminating timber into a beam'
> As suggested 3 ply but the span for that is too much, so a center post is needed too. posts are 6x6
> The confusing part is??



Never glue a lam beam?  Am I reading this right? Why would this be?


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## UlyssesSign (Feb 28, 2018)

Sparky617 said:


> Not sure this is a modular or a mobile home. The OP called it a mobile home.  Most modular homes are minimally a double-wide unit and not a single 14' wide unit.
> 
> Regardless, 2x8's are too small for the floor joist without a beam.  Single wide units aren't designed to be removed from the steel trailer base.  His sag issues are showing that to be the case.



From sifting through the replys I should be able to go 3x2x10 lam beam.
Could I squeeze 10' spans?


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## nealtw (Feb 28, 2018)

UlyssesSign said:


> From sifting through the replys I should be able to go 3x2x10 lam beam.
> Could I squeeze 10' spans?


 Your pushing your luck but you are just taking the bounce and sag out of the floor. Make sure the crown of all 2x10s are up in the center. Most all will have a slight curve or crown.


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## UlyssesSign (Feb 28, 2018)

nealtw said:


> Your pushing your luck but you are just taking the bounce and sag out of the floor. Make sure the crown of all 2x10s are up in the center. Most all will have a slight curve or crown.



This was my thought when it came to the beam. It's only really supporting a 7' span I didn't think I would have to go too crazy. 
Honestly I thought 2x8s would do it, I thought wrong.


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## nealtw (Feb 28, 2018)

UlyssesSign said:


> This was my thought when it came to the beam. It's only really supporting a 7' span I didn't think I would have to go too crazy.
> Honestly I thought 2x8s would do it, I thought wrong.


 You would be back again putting in more posts.


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## UlyssesSign (Feb 28, 2018)

I am realizing that now. So 2x10's it is.


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## Sparky617 (Feb 28, 2018)

UlyssesSign said:


> I am realizing that now. So 2x10's it is.



The bigger the beam the wider spacing you can have on your posts.


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## Gary (Feb 28, 2018)

UlyssesSign said:


> Never glue a lam beam?  Am I reading this right? Why would this be?



It looks like Neal is talking about nailing 2 -2''x's together, not a lam beam.


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## nealtw (Feb 28, 2018)

Gary said:


> It looks like Neal is talking about nailing 2 -2''x's together, not a lam beam.


 Same for LVLs.  I have bolted one LVL beam together and it was a four ply 19"x 22 ft. He wanted it bolted because the load would only be landing on 2 on one side.


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## UlyssesSign (Feb 28, 2018)

Sparky617 said:


> The bigger the beam the wider spacing you can have on your posts.



Well since that's out of the way, thanks everyone for there help and input, 

How could I go about removing some dirt from under there?. 
I'm looking at about 1,100 cu/ft.

I wonder.how.hard a conveyor system would cost to build.


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## Snoonyb (Feb 28, 2018)

You said you already had 5', how much more do you need?


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## UlyssesSign (Mar 1, 2018)

Snoonyb said:


> You said you already had 5', how much more do you need?



5 ft. In most of the space. But about 40' of dirt 2' high was left on one end. 

I'd like to have it all flat and use a 12mm Polly to make the area a dry space for worrie free storage


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## Snoonyb (Mar 1, 2018)

Thanks.

The general rule for excavating in the area of a foundation is 1:1, 1' deep, 1' away, or a 45 degree angle away from the top of the foundation.

Here on the truly left coast, we'd raise the house, excavate, form and pour, wait 28days, set the posts and header, then drop the house.

Concrete doesn't reach full compressive strength until 28days dry.


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## UlyssesSign (Mar 1, 2018)

Snoonyb said:


> Thanks.
> 
> The general rule for excavating in the area of a foundation is 1:1, 1' deep, 1' away, or a 45 degree angle away from the top of the foundation.
> 
> ...



I would love to do this but I don't have 15,000$ to put in the house.


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## Snoonyb (Mar 1, 2018)

When I was a lot younger, and a lot thinner, it was my job to be the "topos" IE, groundhog. I got to excavate when we were doing what your project is, raising and leveling post and girder raised foundation dwellings, only we had usually 12" to work in, so the excavation amounted to enough space to squeeze under a 6" girder, and a pocket for a 5ton bottle jack.


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## UlyssesSign (Mar 2, 2018)

Snoonyb said:


> When I was a lot younger, and a lot thinner, it was my job to be the "topos" IE, groundhog. I got to excavate when we were doing what your project is, raising and leveling post and girder raised foundation dwellings, only we had usually 12" to work in, so the excavation amounted to enough space to squeeze under a 6" girder, and a pocket for a 5ton bottle jack.



feel like popping over for a beer? il get some pizza too


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## oldognewtrick (Mar 2, 2018)

UlyssesSign said:


> feel like popping over for a beer? il get some pizza too


The operative words in snoonby's post was "a younger/thinner"....I'm sure he'd still love to have beer and pizza though...


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## Snoonyb (Mar 3, 2018)

It'd be an adventure, alright.


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## UlyssesSign (Mar 4, 2018)

Thanks guys. 
Turned out I can just call a struss company. There engineer did all the math for me and said I would good with tripple 2x10's  posts at 10' intervals. 

Thanks for all the input.


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## slownsteady (Mar 6, 2018)

How do you plan to take the sag out of the 2x8s?


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## UlyssesSign (Mar 6, 2018)

slownsteady said:


> How do you plan to take the sag out of the 2x8s?



By supporting the floor joists down the center of the building,
3 ply 2x10 by 65'


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## nealtw (Mar 6, 2018)

UlyssesSign said:


> By supporting the floor joists down the center of the building,
> 3 ply 2x10 by 65'


 It sags  over years and you can't expect to lift that up quickly. You put some pressure up and increase the height over days and sometimes weeks until the floor is level.
Lifting and leveling is different than just supporting in place. 
And we had not discussed that earlier.


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## Snoonyb (Mar 6, 2018)

UlyssesSign said:


> By supporting the floor joists down the center of the building,
> 3 ply 2x10 by 65'



In the example I provided earlier, we were under contract, and it wasn't a time and material contract.

3 to 5 bottle jacks were set and the house was lifted until the door molding miters were closed and the doors the hadn't been altered fit. The miters were the criteria.

Doors that had been altered were squared, hinged and filled, or replaced in kind.

The 4x4 post under the girder were replaced, the jacks and blocks were pulled and we were paid.

All in a days work.

Your case will be slightly different.

Complete you excavation, form and pour your pads, set your anchors.

Here begin your options; House movers use cribbing, jacks and beams to lift a house. You can build a simple series of platforms to support you header material during assembly, just keep in mind you do not want any joints within 4' of each other, use blocking to raise the assembled header into place, then use jacks and 4x4 post to raise and level the floor, then set the 4x6 or 6x6.

The 4x4's are sacrificial.


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## nealtw (Mar 6, 2018)

Snoonyb said:


> In the example I provided earlier, we were under contract, and it wasn't a time and material contract.
> 
> 3 to 5 bottle jacks were set and the house was lifted until the door molding miters were closed and the doors the hadn't been altered fit. The miters were the criteria.
> 
> ...


 Our engineers want all beam joints are over the post with Simpson straps tying them together and to the post.


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## slownsteady (Mar 6, 2018)

nealtw said:


> It sags  over years and you can't expect to lift that up quickly. You put some pressure up and increase the height over days and sometimes weeks until the floor is level.
> Lifting and leveling is different than just supporting in place.
> And we had not discussed that earlier.


What he said.........:thbup:


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## UlyssesSign (Mar 6, 2018)

nealtw said:


> It sags  over years and you can't expect to lift that up quickly. You put some pressure up and increase the height over days and sometimes weeks until the floor is level.
> Lifting and leveling is different than just supporting in place.
> And we had not discussed that earlier.



O ic what your getting at now. 
The question seemed a little retorical. 
I plan on slowly raising the floor the required amount over time. 
I'm just going to snug it up then crank it up a couple turns on the jacks and wait a week or so. 

The beam is more to take the bounce out of the floor rather then risk of the floor caving in.


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## nealtw (Mar 6, 2018)

UlyssesSign said:


> O ic what your getting at now.
> The question seemed a little retorical.
> I plan on slowly raising the floor the required amount over time.
> I'm just going to snug it up then crank it up a couple turns on the jacks and wait a week or so.
> ...


 Go to fast and you can lift an outside wall, it's not like lifting a center beam in a rancher.:trophy:


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## UlyssesSign (Mar 6, 2018)

Man you guys are awesome, thanks

I plan on staggering the beam in 3 lengths like flooring.


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## UlyssesSign (Mar 6, 2018)

UlyssesSign said:


> Man you guys are awesome, thanks
> 
> I plan on staggering the beam in 3 lengths like flooring.



As soon as I said it I realized thats a.bad plan. 

Should be Basically like this? 

--------------------  
-----
---------_


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## nealtw (Mar 7, 2018)

UlyssesSign said:


> As soon as I said it I realized thats a.bad plan.
> 
> Should be Basically like this?
> 
> ...


Up here we haven't done that stagger for years we always just but join the beam over a post, It is what the engineers want now.
One said it to me like this. when you cut one ply in a 2 ply beam you now have a fat beam like a two ply with one doing all the work, The extra pieces will stop it from bending but guess where it will break when you load it past the limit of one.


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## UlyssesSign (Mar 7, 2018)

O... well then, I had that all wrong. 
So I need to buy 10' 2x10's rather than 16's


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## Snoonyb (Mar 7, 2018)

UlyssesSign said:


> O... well then, I had that all wrong.
> So I need to buy 10' 2x10's rather than 16's



Hopefully you'll realize that nightmare, before its too late.


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## UlyssesSign (Mar 7, 2018)

Snoonyb said:


> Hopefully you'll realize that nightmare, before its too late.



Yeah I have been waiting to start the project. Just getting the footings geared for now and clearing away as much dirt and debris as I can.


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## Snoonyb (Mar 7, 2018)

UlyssesSign said:


> Yeah I have been waiting to start the project. Just getting the footings geared for now and clearing away as much dirt and debris as I can.



You have your work cut out for you.

The fallacy in splicing composite headers, all composed of equal lengths of lumber, over a post, is that in your case you then have 6 unequal crowns to deal with, which equates to a gold mine for a time and material contractor.

If your going to use that method, then save yourself some of the misfortune by using select grade DF instead of #2. 

The houses we lifted, in a day, in the 1970's were built in the 20's and 30's.


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