I read an article on the JLC website which has an interesting solution to strengthing attic floor joist to convert an attic in an old house to living space.
Instead of removing the old plank flooring they left it in place. They installed 2 x 4 sleepers on top of the old floor planks directly above each existing floor joist. The scribbed the 2 x 4’s to level the floor then screwed and glued them in place. They added a 3/4″ T&G plywood subfloor on top.
Assuming the added depth of the sleepers combined with the depth of the existings joists and plank floor would provided enough strength for the load and span is this something that building inspectors would sign off on. Are built-up joists such as this acceptable.
What do you think???
Mike K
Amateur Home Remodeler in Aurora, Illinois
Replies
Smarter minds here will have other views but I feel your just adding weight. If your not going to sister new joist I would lean more to just screwing down 3/4"plywood to the existing decking without using the 2x4's.
But personally I would do neither and just beef it up with appropiate new sistered joisting.
Not sure what you mean by just adding weight? Seems to me you are adding depth which would strengthen and stiffen the floor.
My main concern is whether the floor joist/plank floor/sister joist crosssection will act the same as a joist of similar depth. I guess it all comes down to how well they are connected, no?Mike K
Amateur Home Remodeler in Aurora, Illinois
I also think they did nothing to strengthen the floor. Just flattened it. Maybe temporarily.
A leader in the Democratic Party is a boss, in the Republican Party he is a leader [Harry Truman]
Boss,
WHY does it not strengthen the floor? I'm not questioning your opinion, just trying to understand the principles involved.Mike K
Amateur Home Remodeler in Aurora, Illinois
I said I don't believe it added strength because all they did was lay boards on the floor. That did nothing but level it.
To add strength, they would have had to sister the existing joists.If flying is so safe, why do they call the airport the terminal?
Boss,
Not sure if you read the article right. It says:
"Next, we temporarily fastened
2x4s on edge directly above
each existing floor joist."
Seems to me if you are placing a 2 x 4 on directly on top of an existing joist (say a 2 x 6) and fastening in an acceptable manner that the effective size of the joist would be increased, no?
So the only question that remains is if having the 1" thick flooring sandwiched between would compromise the strength.
Mike K
Amateur Home Remodeler in Aurora, Illinois
Placing one board above another one does nothing UNLESS the joists are directly connected together. (Like with plywood gussets)Leadership is the initiation and direction of endeavor in the pursuit of consequence. Anything else is criticism from janitors. [Royal Alcott]
Boss,
Again I'm not trying to question your opinion, just trying to understand. Why would lag screws through the top not be an acceptable mention of fastening the joists to the sleepers???
Thanks for your help.Mike K
Amateur Home Remodeler in Aurora, Illinois
Why would lag screws through the top not be an acceptable mention of fastening the joists to the sleepers???
Did not see any mention of the fastening through until this last post. That being said, the size (diameter) of the lag bolts will be as big an issue as the depth of penetration into the member below.
A lumber section 7" thick has a solid, as in treated as full depth uniform adhesion, this is something a 2x4 fastened to a 2x6 would not truly have (would you buy a two-ply gluelam?)
I'm still trying to wrap my head around "temporarily" fastening down anything with a lag bolt; lags are awful permanent in my book (wouldn't backing them out leave some monster holes?)
The real issue for strength is not in the member depth, but it's bearing & attachment. I can't use a 2x8 12' to splice together (only in the center)two 2x4 13'-3 1/2" and span a 26' garage as an "averaged" 2x6 ceiling joist. (Saw that, once; proud HO was not happy to have the span tables for 2x6 @ 24" O.C. consulted.)
Personally, for attics, my choice is to create a separate floor system that spans from bearing wall to bearing wall, and completely separate from the ceiling below. This avoids many hassles. Like adding weight (and, therefore deflection) to existing walls below. Or covering up an insufficient floor structure, which will be eventually discovered, and create even more problems down the road.
But that's my preference, others differ.Occupational hazard of my occupation not being around (sorry Bubba)
CapnMac,
If you read the article carefully it says they temporarily fastened the sleepers with nails in order to mark the scribe line. Then they removed the sleeper to cut it. When the reattached it they glued it down with contruction adhesive and fastened with decking screws.
Unfortunately the article declines to say whether they were putting the sleepers in merely to level the floor or if they were trying to strengthen undersized joists.
I'm considering this method both for the cost and labor savings. I have 2" x 6" joists in my attic. The flooring is 1" thick planks. It would be cheaper and easier to add 2 x 4s to the top of the joists rather than having to pull up all the floor planks and sister in 2 x 10's. That being said if this is not an acceptable solution from a structural standpoint then I will do the full sistering.
I suppose in the end I would have to get an engineer to sign off on this method in order for the Inspection to accept it.
Thanks for your imput!Mike K
Amateur Home Remodeler in Aurora, Illinois
rather than having to pull up all the floor planks and sister in 2 x 10's.
Sometimes, that's less work than it sounds. Doesn't make it any nicer, or less dusty, or less messy; won't keep you from striking either a rafter or a joist, hard, repeatedly, with some (or many) portions of your anatomy. However, those 1" boards have a character that cannot be duplicated--why cover them up as a sub-subfloor (or buld a mouse run)?
Now, don't get me wrong, I'm not down on your project, or for using a working solution for it. It's more caution on my part. I've been in one to many attics, on one too many hot Texas days--I don't like to take anything for granted. Getting up the floor may find as may treasures as tricks. Hope so, at least.Occupational hazard of my occupation not being around (sorry Bubba)
I'm old fashioned, I'd probably pull up the planks, sister some 2x10's to the 2x6's (or better, depending on how much ceiling room I had and what the stairway situation was), put underlayment down on the 2x10's and if the planks were suitable use them for a finished floor surface. But sure isn't an inexpensive route, nor time saving.
If the planks aren't suitable for finished floor, maybe substitute them for the underlayment and put your T&G on top.
Its probably worth a few hundred $$ to get an engineer in there to tell you the best way to do it. He should also be able to tell you if the structure as a whole can handle the additional load.
Capn, you've got me curious with your separate floor idea. You're just creating a floor joist system in between the ceiling joists? So the 'floor' 2x10/2x12's just land in the middle of the ceiling joist span and then use the underlayment to tie them together?jt8
You're just creating a floor joist system in between the ceiling joists? So the 'floor' 2x10/2x12's just land in the middle of the ceiling joist span and then use the underlayment to tie them together?
Well, I'm assuming open joist bays, and the ability to go from bearing surface to bearing surface (not always two easy assumptions to make).
After that, yes, it's as if "proper" floor joists were spanned across the space during the original construction. The floor loads from the top, just like "normal." Now, I've had to figure out how to get ceiling "effects" in and amongst rafter trusses--where you can't add or subtract anything. Hard to sister to the bottom chord of a truss, and not "bust" its design. But, sometimes you just "gotta." BTDT, I'm sharing the t-shirt . . .<g>Occupational hazard of my occupation not being around (sorry Bubba)
It might be O.K., if it was engineered. But I suspect you'd need a heck of a lot of them.
And it wounded more like they were just guessing about what would work.A leader has two important characteristics: first, he is going somewhere; second, he is able to persuade other people to go with him. [Maximilien Francois Robespierre]
"And it wounded more like they were just guessing about what would work."
Where do ya think "engineering" comes from?
it's not in the book until someone tries it first.
Jeff
"Where do ya think "engineering" comes from?
it's not in the book until someone tries it first."
That's probably one of the more ignorant posts you've ever put on this board. You don't just randomly try new stuff one someone's house and see if it works.
New ideas/productsgo through an extensive testing process. Like new styles of truss plates, for instance. Hundreds of full scale tests have to be done and observed by 3rd parties. Then the results have to be published, and a reasonable time allowed for interested parties to comment and/or object.
Then the resulat are submitted to code governing groups for review. They may or may not adopt the new idea and/or design methodology and/or product.
You don't just throw something in someone's house once, then stand there with your hands on your hips and say: "Looks good to me".A wise man knows everything; a shrewd man knows everyone.
That's probably one of the more ignorant posts you've ever put on this board.
So you really don't think home building evolved from "tried and true" ideas?
I figured you'd have a reaction like that. Too much time behind a desk ... barely none on the field. Too much reliance on calculators and books .... not enough watching and learning.
years back ... had a great carp instructor in trade school ...
when we got to the "remodeling" part of the course ...
he said some very true words.
"If you are going to go out and do remodeling full time ... real remodeling ... just about every day you will do something ... and think ... that "should" work"" ....
Guess what ... he's right.
Quick .. what size header do ya need for a 6' opening?
and why?
Because the code book said? because U hired an engineer to check the code book?
Or because U know by watching others that a doubled 2x8 will suffice?
How much engineering you think was done in homes 2 and 3 hundred years old?
Ya know how the ones 1 to 2 hundred years old got built ... they just build them the same way the old ones that were still standing were built! And if the old ones were leaning .. they upsized some of the framing.
You want to hire an engineer for most any jobsite question ...
no wonder you can't afford to build a house that'll sell at a reasonable price.
Lose your attitude.
Stick to trusses.
Jeff
Sorry, I forgot - You're still young enough to know everything.
Talk to me again when ya grow up.Never argue with an idiot, they drag you down to your level and beat you with experience.
I saw an interesting concept on TOH (ok I tune in when nothin else is interesting) an Ted Benson the big timber framer, has a neat system, they laminate a bunch of 2x4's side by side, and create large panels ...like a flat glulam.
These are the second floor, they are spaced off frame with, adjustable bolts to create a chase for ele. and rats.
I too have a situation where, my ciel joists are way undersized and overspanned, but the second floor wood is exposed as my cieling downstairs..beaded T&G.
This 'new' idea of a 2x4 or more scribed to the sag MIGHT fly, but my gut says no. I'd be inclined to respan from bearing to bearing but that would increase the overall thickness and lower the up stairs head room too much..( basically a story and a half not true 2 story)
I think I will try taking a shot at this over one of my joists and see if it really helps,the flooring is pretty ruff as it is, nothing much to lose. I will do it with out the glue or added new floor, and see if it stiffens anything.
In my situ, sistering is not an option, open joists are staying open.
Any other ideas?
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
I don't think glueing a 2x4 on top of a 2x8 will make it as strong as a 2x10.