Adding structure to an overspanned floor
This will take a bit to describe what i’m trying to do and reason of wanting to do certain things. I’m looking for advice or comments on anything I can do better.
I have a small Cape Cod style home from the late 1920’s. The upstairs is a very under utilized space. There is a full set of stairs up to the second floor. The second floor currently has no heating/cooling or bathroom. The idea is to add those two previously mentioned things to the second floor.
The second floor has a 3/4″ heart pine floor over 2×6 joists. The heart pine floor is going to be taken up to be replaced again after restructuring.
Problem: The floor joists of the 2nd floor are 2×6’s spanning 15′, not enough structure to use the spaces for living. The ceiling of the first floor is plaster with wood lath. There is one major loadbearing wall in the center of the house on the first floor and the two exterior walls.
Other Problems: Because of the angle of the roof and its proximity to the 2nd floor level and exterior wall it makes for a tight space to get down into that corner. Because the ceiling is plaster with wood lath there is a significant amount of plaster that is seeping through the lath that i wish to leave undisturbed as to not disrupt the plaster ceiling below.
Obviously sister joists is an option but that would most likely cause ceiling disaster below.
Is flitch beaming an option? And how creative can I get with flitch beams and or any other creative suggestions.
Thanks
Austin
(young architect with old house)
I can attach drawings of what how I intend to ‘flitch’ if needed.
Edited 3/28/2008 2:27 pm ET by ArcoSU
Edited 3/28/2008 2:28 pm ET by ArcoSU
Replies
Is the load bearing wall perpendicular to and supporting the joists? Where does it fall under the 15 foot span?
the joists are perpendicular to the exterior wall and the load bearing central wall at the first floor. the 15 foot span is between the central locad bearing wall and the exterior wall, the house is basically symmetrical.
Edited 3/28/2008 2:50 pm ET by ArcoSU
OK. So you'll have to sister 2X12s. Can you block them up on the bearing ends to avoid breaking up the plaster?
Thank you this is a good option, just getting into the tight corner where the roof and floor meet will make it difficult to place a shim.
Thank you this is a good option, just getting into the tight corner where the roof and floor meet will make it difficult to place a shim.
If you can figure out what size blocking will raise the new joists above the plaster, you can nail it to the joist prior to putting them in place.
You needn't get in there and nail the block/shim to the bearing surface, as long as the joists are sistered and well fastened together.
BTW, fastening with screws will help you avoid damaging the plaster.
Two good points there Hudson. There's no reason to nail the ends of the new rafters to the old ones. Tack on the shims, put the joist in place, and nail it well in the middle.
And using screws will definately take a lot of shock out of the construction. he just needs to be sure he doesn't use screws in a shear application."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Why not?So long as they are not SR screws and are designed for shear loads.Let's say he uses some good PL Premium to sister with. Then the screws can suck the wood together nicely - better than nails would there over that plaster ceiling - and hold it until the adhesive kicks. I would use some #10 x3" GRK at about 16"OC
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Well, if you add the caveat that the screws are structurtally rated, then it's not an issue. But that presumes that the user doesn't just but SR or deck scrwews from the big box."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Now for the touche~Are you going to specify that your nails should not be 15Ga headless pinners?
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Picky, picky."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
That's a great idea, thanks so much
That's a great idea, thanks so much
I noticed that you said you're a young architect. On behalf of the many creative craftspeople who give much to the building trades may I suggest that you continue working with both your mind and your hands, even as a pleasant hobby, and continue asking us to solve practical problems for you. Doing so will serve you and your clients well throughout your career.
With Respect, Peter
Edited 3/30/2008 2:52 am by Hudson Valley Carpenter
I couldnt agree with you more, and as a young architect and aspiring woodworker I love to do as much work myself as possible, and I like to gather knowledge from the people who know the most, ie. people on the finehomebuilding forum, the true craftsmen. My last resort is to ask a fellow structural engineer whom i work with frequently to see if he has any reccomondations on the vairous solutions i will put in front of him, i began here because i know it is something that had to have been done before and i knew there has to be more than one way to do it. some of the email chains have diverted from the conversation and became arguments on personalities, i wish people could have stuck to the point more.
Edited 3/30/2008 12:39 pm ET by ArcoSU
ArcoSU
I reread all of the posts here and while there was spirited debate I suspect the exchange between Piffin and I is what you are referring to.
I hope you saw the smiley face he posted to understand it was good natured kidding and not any real animosity..he and I often differ on things and yet enjoy the exchange.
Spirited debate is normal here and only rarely in the tavern where political and other controversial subjects are debated do things sometimes get carried away.
i wish people could have stuck to the point more.
I'm glad that you said that. Some people who post on this board are enthusiasts on a mission while others have years of daily work in the trades.
Most of the professionals ignore sketchy opinions from the DIYers, contenting themselves with offering complete and concise suggestions based on multiple experiences with the topic under discussion.
Other pros believe that misinformed and misleading advice from enthusiastic amateurs should be challenged.
I'm usually too lazy to argue with amateurs but I sincerely wish that they'd take a back seat, waiting until the professionals have given their advice before getting involved.
That way they'd discover where their experience is lacking without taking up the time of others who come here looking for advice from those who are qualified to help them.
"...pros believe that misinformed and misleading advice from enthusiastic amateurs should be challenged.I'm usually too lazy to argue with amateurs but I sincerely wish that they'd take a back seat..."There was a story in the paper the other day. Lady drops one of those new compact florescent bulbs on the floor and it breaks. She remembers hearing something about dangerous chemicals (a tiny bit of mercury) so she calls some county office about what to do. The county office gives her the number of a hazardous waste clean-up crew. She calls and they give her a quote of $2000 to come clean it up.All of the people involved there (except the lady) were professionals. All of them were idiots. Any DIYer would have suggested she get a brush and a dustpan and clean it up - wipe the floor with a paper towel and throw it away - job done.Now, that was an unusual example to make a point, and I don't think for a minute that anyone ought to ignore the advice of professionals as a general rule or take anything anyone says as gospel truth without questioning their experience. But my point is that lots of people have lots of different kinds of experience and the quality of their advice does not necessarily have much to do with whether or not they have managed to get paid to do similar work.In any case, internet advice such as this should ALL be taken with a grain of salt. We can't see the problem well enough to claim educated advice and the homeowner has no idea whatsoever who's response is from a professional, DIYer, or a 14-year-old pimply-faced kid sitting in front of his computer getting his kicks pretending to be someone else.
But my point is that lots of people have lots of different kinds of experience and the quality of their advice does not necessarily have much to do with whether or not they have managed to get paid to do similar work.
Granted. Except that in the present case, home building and remodeling, a disciplined approach must be learned in order to be efficient, competitive and profitable.
So advice given by a person who has achieved enough skill and efficiency to earn a profit, for him/her self or his/her employer, is of greater value than are the ramblings of someone who has only managed to figure out one way to accomplish a particular task in his/her own good time.
Edited 3/31/2008 1:55 am by Hudson Valley Carpenter
"Other pros believe that misinformed and misleading advice from enthusiastic amateurs should be challenged."I'll confess.
To me it is often a matter of maintaining the integrity of this forum. If it is left to all the DIYs to swap misinformed mythology with one another, it loses its value and becomes as worthless as the Bobvilla forums and some others.So far BT maintains a decent balance between that kind of idiocy and the extreme close-mindedness of JLConline
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To me it is often a matter of maintaining the integrity of this forum. If it is left to all the DIYs to swap misinformed mythology with one another, it loses its value and becomes as worthless as the Bobvilla forums and some others.
I'd say that this thread makes a clear case for your position.
It also makes a good example of one of the strong points of this forum.Like Frenchie mentioned, he and I fight a lot, but sometimes have a certain amt of respect for each other in the fields of our respective strengths. seems that you and I have tussled a time or two also, but we are both professionals with high standards and different backgrounds and experiences. We both have some respect for the others opinion, even when it differsMix stuff together, stir the pot and apply a little heat and the cream will rise to the top. A little discernement and smart OPs can find good advice here.
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A little discernement and smart OPs can find good advice here.
Or they can learn how to be more discerning. LOL.
It may turn out that this means of communication is a real boon to developing the intuitive side of human nature. Then again, it'll probably foster some imbalance too. Every stick has two ends.
Edited 4/1/2008 2:17 pm by Hudson Valley Carpenter
AMEN!
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ArcoSU,
How well made is the ridge beam?
If it's relatively sturdy perhaps you can carry the floor by hanging from that.. that would cut the span of the 2x6's from 15 feet to 7 1/2 feet.. depending on what exactly we are working with it's possible to use a beam from the ridge beam in tension to carry some of the laod.. it won't be perfect and you might need to carry a few but it should help somewhat..
I'd suck it up with a come along to take all possible sag out and then connect the ridge to the floor joists.
If you don't have a strong enough ridge beam there are a few other approaches you could use depending on how the roof is framed how the floor is framed and what you are willing to sacrafice..
there is no sag at the moment the idea is to not create sag when we make the upstairs livable. hanging down from the ridge beam would cut the space in half which contradicts the use of the upstairs, its a very small house about 30'x70'
ArcoSU,
You wouldn't need to build a wall, just enough load carring beams to transfer the strength of the ridge beam. You can be relatively clever about that.. I'm not saying it's the only answer just trying to get you to look at things from a differant perpective.. Look at old fashioned hammer beams for insperation.. not that you need to timberframe this but by transfering load you can easily span a lot greater distance than would otherwise be the case..
Did I understand there is a divide below the span? What's to prevent that from being the loading member?
I'm sorry, I don't fully understand what you are suggesting. I will look up hammer beams.
ArcoSU
When you find them you will see they are large timbers used in timberframes.. Well don't think of them in those terms follow the load path and note the strength remains nearly the same if you were to use them as dimensional lumbers the way your house is built..
Don't invest too much effort in trying to understand frenchy on this one. he has a good idea once in a while, but he is out to lunch on this whole scheme
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Piffin
I freely admit I'm guessing here because so far he has't told me if his ridge beam is strong or weak & what his roof truss boards are made of..
IF the roof is overbuilt you can hang the load from the roof and lose less headroom (always a critical issue in the attic)
As I said in the whole post look at other solutions too.
reason I think your idea is off on this is that it makes no difference what his ridge or boards are. The sizing of the rafters is what would make your thoughts possible or not.
That is one element you have not even mentioned.
And if this is like 99% of all the capes from that era, the rafters are at least as overspanned as the floor joists
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Piffin,
Two posts above I asked that question and very early on that was the first question I asked..
You are correct in that I don't know.. I said as much and merely asked the question.. There were already several posters along the line most advocate so I really couldn't have contributed anything new in that respect. That's why I went a differant direction..
I've little experiance with east coast construction techniques. So I don't know if those techniques reflected construction around the same time here which tended to be a bit over built. Wood here is cheap and plentyful. So a lot of the Farm houses built in that period were overbuilt to withstand our winds and weather..
Frenchy, capes are usually built with a center bearing wall that supports the second floor joists. That's probably what the original poster has. It's not the center support that's an issue, it's the span from the outside wall to the center wall.
The only way a strut hanging from the ridge would support that part of the span is if it was at an angle, which would ruin any chance to use the upstairs. Hanging the floor directly off the rafter would more than double the design load of the rafters, which are most likely already undersized by modern code.
That's why it's almost a certainty that somehow beefing up the floor joists is a better solution than hanging the weight off the roof system.
Way to think outside the box though!
The way I have Frenchies idea picutered to be able to work would have the floor hanging from rafters about 2/3 of the way down from the ridge - or 5' in from the ext wall where most cape kneewalls are built. That puts the load on the rafters and forces them to sag there before it is of any consequence to the ridge, if there is one.
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Mike
I had imagined a simple post going up to the ridge beam designed to cut the span in half. I'd have to look up what wood in tension is capable of handleing and check to verify that I could use few enough of them that they wouldn't form a defacto wall.
The other way would be a modified version of a hammer beam
About where you'd put a knee wall in you put the rafters in tension. I don't know if that would result in a short enough span that the 2x6's would be adequite but it's worth a look.
However if Piffin is correct it's all moot because small and undersized ridge beam and or rafters eliminate that possiblity..
I had imagined a simple post going up to the ridge beam designed to cut the span in half.
Sorry Frenchy,
While I have seen your solution done on some commercial projects (mostlky to create additional storage, not living space), I have never seen it done in a residence. Especially a cape cod.....they almost never have a "ridge beam".....at best a 2x8, but most of the time just a 2x6.
The way most Capes are framed, the opposing rafters are in compression at the ridge, so they do not need a beam. The OP's 2x6 "ceil/attic joists" are actually in tension (think bottom chord of a truss), and are usually nailed alongside the rafters at the plate location. As such, in order to use the "hanging" method, the entire roof will have to be re-structured.
I agree w/ Piffin. While this is an option, I do not think it is the best one for this job.
I also disagree w/ another poster's (a wood worker to boot) mention of the ease, speed, and cost effectiveness of bolting steel flitch plates along-side each joist.
I heard recently....."Anyone can make a structure strong enough. The real feat of engineering is to make it strong enough, light enough, easy to build, and cost effective."
My money is still on sistering up w/ (in this case) 2x10's or 2x12's. I have done it many times. It is not complicated, and it requiores no specialized tools or knowledge.
I would do it with 2x10s myself, especially since the OP is rebuilding the stairs.The ace carpenters idea of bolt on plates does seem far to difficult and costly to me, but if headroom /elevation is an issue, it would be a solution worth investigating.What I like about the engineer I have most used, is that he will engineer me 2 or 3 solutions, and let me decide which to employ, depending on access, manpower, cost to install, etc. Just like with computers, there is always at least three ways to get something done.
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Just like with computers, there is always at least three ways to get something done.
I absotively posolutely agree w/ that philosophy 110%.
pickings,
True enough but finding let alone getting 30 foot long 2x'10's or 12's up into an attic won't be easy either.
You aren't a paying attention!There is a supporting center bearing wall in the middle of the building. The joists only need to be 15' plus overlap so typical sixteen footers will work just fine.
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"That's why I went a differant direction.."That what I pointed out - that you were outside wandering around in your imagination while we were in here working on viable solutions.;)you kept referring to th eridge BEAM which is directly above where he already has a wall supporting under this. The house is 30' wide. That supporting wall and the ridge are at fifteen feet. But somehow you are trying to hang the midpoint of the floor to the ridge, another 7.5 feet away. The only way to support the middle of the floor joists vertically is to the rafters in their midspan.You never mentioned the rafters, you kept pointing to the ridge
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Piffin.
Then I misread the post. I read it as if he had to span 15 feet not 30 feet.. Getting 2x6's to span 7 1/2 feet is doable depending on spacing etc.. I did mention roof trusses, I should have said rafters. However it was never established what size we were working with in spite of questions..
If your guess is correct that everything is undersized then it's all academic
Obviously sister joists is an option but that would most likely cause ceiling disaster below.
Not necessarily.....Have done this in the past sucessfully.
The key is to shim up the new joists at the front, rear, and intermediate walls. 3" X 12" strips of 1/2" thk plywood works well. This allows the new joists to still bear on the same load points, but not touch or interfere w/ the exist plaster ceiling. The new sub floor is then fastened to the tops of the new joists only.
If you plan on using an existing stairway, you have to use 2X6's to sister so as not to change the top riser too much (only 1/2" higher). Make sure you nail the heck out of them all along the lenght. Remember, you are trying to make 4x6's.
If a new stair will be installed, I would reccomend you consider sistering w/ 2X8 if you will be fastening to the existing joists all along the lenght, or use 2X10 and just put them in between the exist joists, but not fasten them together. You still have to use the plywood shims, but this last method will totally isolate the new floor from the exist ceil.
This may not be the perfect approach, but has worked well for me on more "add-a-levels" than I care to remember.
Good luck
Thank you this is a good option, just getting into the tight corner where the roof and floor meet will make it difficult to place a shim.
not really..... cut a bunch of em, a dab of const adhesive on the bottom, then lay down, reach over and lay them puppies in there.
Not clean, not comfy, but once cut, you can probably install all of them in less time than you will spend reading ideas here.
PS. you still gotta reach back there to sister the joists up......just watch out for the roofing nails.
Thanks, I mean your reccomendation right now is the best I've got and first I've thought of and probably what I will do in the end, I've also talked to some co-workers about placing a 2x4 over the existing 2x6's with a plywood flitch type attachment to tie the new to old, this way i can create the 2x4 with plywood in advance and slide them down to the end where they meet the roof, then nail to existing as needed. But thanks, all of this helps and yes it will take me more time to read these, but it'll be for the better in the end.
Never hurts to hear all the ideas first. Makes for fun reading sometimes too. Good luck w/ it.
That 2x4 "joist height extender" sounds interesting. Needs a new stairway though. Will keep it filed away in the cobwebs/fog of my mind for future reference.
Again, good luck
PS I also have fun working on my old 1852 Greek Revival.
Thanks, redoing the stairs is part of the upstairs renovation phase. right now they are a bit ugly, i'd like to make them nice heart pine like the rest of the house.
Adding a 2x4 on top of a 2x6 does not give the same strength as a 2x10."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
I agree, but i would flitch beam them to top 2x4 to the bottom 2x6 with at least 3/4" ply on both sides.
If you don't mind losing the headroom, stacking 2x4s as you describe would likely be the easiest method and least likely to disrupt the ceiling below (as long as you glue and gun nail or screw and avoid using a hammer).
But this is not a flitch beam, which is a sandwich of wood and steel. What you are describing is a box beam and it would be far stronger than a 2x10.
Go for it.
Riversong HouseWright
Design * * Build * * Renovate * * ConsultSolar & Super-Insulated Healthy Homes
That still does not give you the load bearing capacity you are looking for. Best to sister in 2x10s
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cut the joist sister, then crown it, roll it over and tack the shim to the joist first, then slide it into place.
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I didn't read all the posts here, but I had a similar situation with our attic. Our span was not quite so extreme as yours - our 24' wide house had 2x6 on the attic floor (with plaster & lath below) and the load bearing wall in the center of the house was offset a bit so that one side spanned about 13 1/2' and the other 10 1/2'. But I was concerned, too & didn't want to disturb the ceiling below. What I did was to build the knee-walls the entire length of the roof, screwing the top and bottom plates into the floor & roof joists and then sheething the wall with 1/2" plywood, creating something like a box beam which helps carry and even out the loads that might occur on any one point. Since I'm not engineer, just someone who tries what seems sensible, I can't tell you if your situation is similar enough to do the same thing. But it worked for us. We have three children who use that space as a play area - jumping around and being loud - and so far (7 years) there has been no cracking of the plaster ceiling below. The attic floor is perfectly comfortable to walk on, though I would think twice before putting a king size waterbed up there.Good luck.
As a master carpenter, I've done many jobs that sounds identical to this and the easiest thing to do, with the cleanest installation, would be to get 3/8" thick by 4-3/4" by approximately 4" shorter than your span with holes predrilled 1/2" diameter and lay flinch plate beside joist, drill through and bolt together, and if your going to have any load other than light furniture, I would suggest doing it on every single one (add a flinch plate to every joist) and anywhere that bathroom walls may fall on top of joist, I would put a flinch plate on each side.
Elite Carpentry Service
Chris Thomas
What is the material costs of using steel plates bolted to the existing joists versus sistering in wood joists? Seems like the steel would be much more expensive, no?
A flitch plate would work. The size you suggest is about as strong as two 2x8's.
But there's no "N" in it. It's flitch.
And who calls themselves a master carpenter?
What a travesty!A MASTER carpenter who suggests using steel?
Get oughta here! just kidding - and welcome to Breaktime. You might want to clear up how many of those 1/2" holes - spacing and pattern - you would suggest.
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And, welcome to Breaktime.
I had my grump on this morning.
Master Carpenter,
What could that mean? Are you typing one handed?
Welcome to the zoo, buckeroo. How do you do?
And how about filling out your profile, at least where you live? So we'll know who to send to shovel you out when the BS gets to deep.
BTW, we had someone in Frenchy's neighborhood but he quit after the first week.
Edited 3/29/2008 11:43 am by Hudson Valley Carpenter