New Studio Build Underway

Document your build here: All about your walls, ceilings, doors, windows, HVAC, and (gasp!) floated floors...
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Starlight
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Re: New Studio Build Underway

#31

Postby Starlight » Wed, 2019-Dec-11, 04:48

You do not have an overly high room and by having two baffles in the loft space where your ventilator/air handler will be and then coming through both the outer and inner ceilings before the inner baffle boxes that would give you more room height everywhere where there are no baffle boxes, possibly a better solution than lowering the whole of the inner room's ceiling just so that the baffle boxes can be between the two ceilings. If I have misunderstood the drawings in the OP and the inner ceiling is just an acoustiucally transparent, aesthetically pleasing drop-ceiling, then what I have said does not apply.

However, as you have employed Stuart to design your HVAC I would not want to try and suggest differently. I have discovered that just as different car manufacturers use different methods and layouts to make a car, so do studio designers. One designer's work is not really intertwineable with another's. Not that I am a studio designer, just a keen amateur.

Great news about the progress with the build, Howie.

As a little aside, I laugh to myself when I see Jay Leno's Garage (on YouTube) and you know it is winter because he has put a jacket on to drive an open-top car. Where I am already has snow and we won't see rain until March simply because any precipitation falls as snow because it stays below freezing 24/7. I hope the California sunshine allows you to continue through the winter.



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Re: New Studio Build Underway

#32

Postby howiedrum » Wed, 2019-Dec-11, 11:27

IMG_4176.jpg
Back porch ready for pour (click on image for correct view)
IMG_4179.jpg
Front porch ready for pour
IMG_4182.jpg
Back porch poured
IMG_4183.jpg
Front covered porch poured with brackets
IMG_4184.jpg
Sill plates prep east view
IMG_4185.jpg
Sill plates prep west view
IMG_4192.jpg
Exterior Wall Framing East & West Sides



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howiedrum
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Re: New Studio Build Underway

#33

Postby howiedrum » Sun, 2019-Dec-22, 16:07

Well it's been a minute since my last post. A lot has happened. The general contractor handed me a change order on Friday to the tune of $16,700. He says the labor for the job has already exhausted what he budgeted for framing due to the steps taken by his builder to account for the caulking under the sole plates and other things. Here is the breakdown of what he is asking me to pay for the following changes:

2x8 roof rafters changed to 2x10 for $745. I am ok with this. Originally we were going to double up on 2x8.

Two layers of 3/4 OSB on exterior wall for $3,625. He didn't account for this when he did the bid. I am not going to pay for this because it is clearly on the plans and the contract states "bid price is for details on the approved plans". I don't understand how he could miss this. It was on every plan I submitted (remember I had to submit three) and I have emails back to April of 2018 with this detail listed.

Framing not able to do tilt up frame. Because of caulking, we had to do stick framing. $4,380. This was a decision his builder chose so the plates could be dropped on top of the caulking as opposed to tilting. I am willing to pay for the extra labor for this but I am going to ask for clarification. I don't think there would be an extra material charge for this. It seems like a high charge.

Interior walls need to be stick frammed for $3,810. Same as previous comment. I want to see a breakdown. Labor only or is he charging me materials too.

Painting/Caulking for $1,920. I am willing to pay for the extra caulking and labor since it wasn't listed on the plan. I want clarification if this fee is for the caulk material or labor to apply or both. And is it just for whats been done up to now or if it covers the future use throughout the build.

Specialties, labor increase for inefficiencies for $2,310. Again I am going to ask for clarification. I think this is mainly for his time trying to answer questions with his builder and additional meetings with me and mostly for the labor to tarp the whole building to keep the OSB dry for the green glue application and to keep the inside dry for the caulking applications. Due to the silencer boxes fitting in the middle leaf and the HVAC between roof and middle leaf, the builder chose to tarp and work his way up from the foundation instead of the opposite. After I met with the general contractor, we both decided to have him take the tarps off and build the roof and have the HVAC brought in through the access door in attic above middle leaf and roof. For the installation of the suspended silencer boxes, OSB, and GWB inside middle leaf, the general contractor has a plan to install from below by putting in an access door to the middle leaf that would be sealed and caulked after completed. I shared with him Stuart's building modules and lifting into place, but they still feel it will take too long and too heavy.

So I am preparing a response to his change order. Basically I will pay for anything not specified on the approved plan, but not if it is. It gets tricky with this whole tarping part. While there is no mention of tarping on the plan, he discussed it with his builder. It makes sense to keep the OSB dry for the green glue, but am I responsible for the methods they use to accomplish the different aspects of the actual construction as drawn on the approve plan? Isn't that his responsibility to figure that out prior to bidding? I want to be reasonable and not stick it to him because I know he is trying to cover himself from taking a bath on this project. But I am also not made of money and I still have to pay for the HVAC, silencer boxes, and any treatments I want to do inside.

In my response I am going to outline every aspect remaining in the building with me paying for things not on the plan and he paying for things on the plan so hopefully there are no more surprise change orders. Basically he is turning this into a T&M job through these change orders. Any advise or comments would be appreciated. I want to email him tonight or early tomorrow.

Thanks and here are some photos.

Ext. Walls up.jpg
Sheeting begins.jpg
Plastic Cover Sheeting.jpg
south side inside view.jpg
Tarp 1.jpg
Inside Wall between studio and kitchenette_bath .jpg
Shimmed OSB.jpg
Water on floor.jpg
Attachments
North side inside view.jpg



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Starlight
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Re: New Studio Build Underway

#34

Postby Starlight » Sun, 2019-Dec-22, 20:25

howiedrum wrote:I will have to stay on top of things with the builder ...


I sure hope you can keep a good friendly, working relationship going with your builder as you need him working with you not against you.



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Re: New Studio Build Underway

#35

Postby howiedrum » Mon, 2019-Dec-23, 15:36

Yeah me too! It's becoming clear that he did not do much research when he bid it. I ordered the green glue, which he gasped at the price and said he didn't bid the $2,000+ for it. I asked him what he did bid for the green glue. No response. Why? Because he never even looked up what green glue would cost is my guess. I want to be sympathetic, but come on. He was lazy with his bidding and now he's unhappy. We'll see what happens. My instincts tell me that he will do the job correctly as planned, but he will try to make up the difference by charging me for anything and everything not spelled out on the plan. Stay tuned!



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Re: New Studio Build Underway

#36

Postby howiedrum » Fri, 2019-Dec-27, 15:29

I spoke with the general contractor regarding his change order. He said he was so far over budget that he was considering not finishing the build. He said he couldn't make his payroll due to "unforeseen extras". He said the requests for clarification of the details of the change order were going to take much more time than he presently has. He said that bidding jobs isn't easy and that costs were way more than he thought.

I asked him when he bids a job and it is completed for less than his quote, does he return that money to his client? Answer Never. I asked him if I didn't realize certain items were on the bid could I later come to him and ask they be included for free? Answer No. I basically let him know that he was trying to turn this into a T&M job and that he has to abide by his bid and the contract we signed and take the loss if he incurs one. He said he could drop $5,000 from the change order, which was his profit. We agreed that I would pay him 10K additional which is about $7000 less than his change order. He will finish everything on the approved plans with no more charges due to framing, sheeting, or caulking. I feel ok, not great about this. The other contractor's bid was about 10K more than this contractor, so I reasoned that I am paying what I would have had I gone with the other guy and I didn't want this to go the legal route and delay the build. Legally it's a slam dunk for me and that's why he settled for less. I could have pushed back more but basically I like his builder, I want it to get done, and if the general contractor had actually done his homework, I would have been paying more than this. Hopefully I can now just post pictures and there is no more drama. Stay tuned!



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Re: New Studio Build Underway

#37

Postby Gregwor » Sat, 2019-Dec-28, 19:19

The place looks amazing and I hope things are awesome going forward. I had the same issue with the guys who built my house as they didn't understand about mass and sealing even though I explained it to them multiple times. Of course to win our business they said "I totally get it" and then once problems came up they said "I'll admit, I have no idea what your studio is about. We are just going to build it the way we normally do and if you want things different you'll have to change it after". Luckily I was able to buddy up with most of the contractors and got most of the issues sorted out.

Greg



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Re: New Studio Build Underway

#38

Postby howiedrum » Sat, 2019-Dec-28, 22:19

Hi Greg,

I recognize you from John's forum. I actually remember some of your story. Yeah I think (we'll see) it's sorted out. We compromised and the vibe is good for now.

I have a building question. Should there be caulking between the two top plates on top of the walls?

Thank you and I'll post more photo's soon.

Howie

IMG_4280.jpg
Top plates with joists on top.



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Re: New Studio Build Underway

#39

Postby Soundman2020 » Sun, 2019-Dec-29, 01:40

I have a building question. Should there be caulking between the two top plates on top of the walls?
If the sheathing will cover that on the outside, then it probably isn't necessary...

That said, my rule for high isolation builds is simple: "If there's definitely a gap or crack, then caulk it. If you think it might be a gap or crack but aren't really sure, then caulk it. And if you are totally certain that it is NOT a gap or crack, th caulk the hell out of it, just in case!".

For very high isolation builds, even minute hairline cracks can leak a tiny bit of sound, and that's all you need to degrade the isolation. So it's better to be safe and caulk everything. Yes, it does mean that you'll be using a ton of caulk... but you already knew that!

Lots of mass, and air-tight seals, are your number one best friends when you want high isolation.


By the way, I'm glad you reached an amicable agreement with the contractor. That's good news. The ten grand extra is likely money well spent, both in terms of covering costs and also in terms of a plain old good relationship with the builder. It's a pity it had to come to that, but I reckon it's a fair deal, and should keep things running smoothly.


- Stuart -



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Re: New Studio Build Underway

#40

Postby howiedrum » Sun, 2019-Dec-29, 16:42

if you are totally certain that it is NOT a gap or crack, th caulk the hell out of it, just in case!".
I love this quote! I will reiterate this to the builder. I raised the question because after he left, I didn't see caulking between the top plates (although there may be) but I did see it where the ceiling joists were connected to the rim joist. I will ask him.

By the way, I'm glad you reached an amicable agreement with the contractor. That's good news. The ten grand extra is likely money well spent, both in terms of covering costs and also in terms of a plain old good relationship with the builder.
Thanks. It is a tricky path to cross. If I just rolled over and paid it, I think he would just keep asking for more. If I pushed back too hard he could have pulled his builder off the job. I was firm but understanding and like I said before, neither of us got 100% of what we wanted but that's how compromises work. It helps to hear that the extra money is worth it. I am so happy to move on from that and I think it worked out a bit in my favor and luckily I have the money to cover it.

Prior to the change order drama, the general contractor and I agreed that the Builder's plan of tarping and building from the bottom up was not ideal. Water had been leaking in and if we got some heavy weather we wondered how well the tarp would hold up. So he was directed to pull the tarp and start working on the ceiling joists and roof and work his way down. To his credit, the builder made improvements to the tarping and the morning before he pulled the tarp it was quite dry in there and held up well over the previous night's rain.

The main question was once the ceiling joists and roof were on and the HVAC and silencer boxes were hung, how would the inner leaf ceiling be constructed. As I have mentioned before, they didn't like Stuart's modules lifted up from below plan. And the general contractor was worried that if mold or other problems were to occur in the 18" space between inner and middle leafs, how would I access it.

So his plan is to work that space starting on the ends and moving towards the center, lifting first a sheet of OSB through the joists and nail or screw (he didn't specify) down and then the green glue and drywall on top, one sheet at a time. Once the first few sheets were assembled at the ends, he would slide the needed drywall on top of the completed ones. Then slide up the OSB, adhere, then gg, then drywall from the ones already placed in the space. He would continue working his way towards the center. Once he has his final piece, he would cut an access door so the builder could get out and then he would plug, and seal this door. Seems like a lot more work than building everything on the floor as a module and lifting up. But what do I know? I will continue to ask about this. Since we are building from roof down now, we have some time to talk about it. The sentiment was that it will be cheaper and quicker to do their plan.

After the tarp was removed, it rained pretty good. Water in the building hasn't been a concern with the builders, but I decided to use my shop vac and suck up as much as possible. It worked great. I got it pretty dry and then we had a number of rain free days and some sun and things dried up pretty good. No more pooling of water. The process of shop vacuuming also helped me connect to the space. It is raining today (12/29/19), then dry for a couple of days and then more rain. Hopefully they will get the roof on before too much rain falls.

Well that brings you up to date. Here are the latest photo's.

Best wishes to everyone and Happy New Year!

1_Tarp Removed.jpg
Tarp removed.
2_Corner fo Kitchenette.jpg
Corner of Kitchette before shop vac
3_Water pooling in studio.jpg
Water pooling in studio
3a_Inside west wall.jpg
Inside view of west wall
3b_Builder loves my dog.jpg
Builder loves our dog Daisy
4_Joists begun.jpg
Ceiling and rim joists prep
5_Joists half way.jpg
High Schooler helps with joists
6_Joists 3.jpg
Joists 3/4 complete
7_Front View.jpg
Front looking west
8_Southeast Corner.jpg
Southeast view. Plastic wrap on to keep dry for green glue app
]
Attachments
9_East View.jpg
East view of kitchenette entrance



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Re: New Studio Build Underway

#41

Postby Soundman2020 » Tue, 2020-Jan-07, 23:11

So his plan is to work that space starting on the ends and moving towards the center, lifting first a sheet of OSB through the joists and nail or screw (he didn't specify) down and then the green glue and drywall on top, one sheet at a time. Once the first few sheets were assembled at the ends, he would slide the needed drywall on top of the completed ones. Then slide up the OSB, adhere, then gg, then drywall from the ones already placed in the space. He would continue working his way towards the center. Once he has his final piece, he would cut an access door so the builder could get out and then he would plug, and seal this door. Seems like a lot more work than building everything on the floor as a module and lifting up.
:shock: I agree! That sounds like a hell of a lot of hard work! Much more than just raising up modules from below. Not sure what he is worried about with that system: Did you show him this thread? viewtopic.php?f=12&t=50 It's really not that hard to do, and since most of the modules are the exact same size, you can make a simple jig to "mass produce" them, one after another. If they are worried about the weight of the individual modules, then they can be made smaller too, so each one is not so heavy, and can be lifted simply by just a couple of people. Or on a standard drywall lift... dead easy. Most good drywall lifts can lift things up to 11 feet high (some go to 16 feet), most can handle 150 lbs load, some can handle 200 lbs, and a couple can handle more than that. So as long as each module is under 150 pounds, a normal lift can handle that. Very strange that they want to do it the had way!

The only problem with their method is: it's going to be REALLY uncomfortable for the poor guy working in a space only 19" inches high! He's going to have to do all that laying down....

It would only take me a few hours to re-design the ceiling so that the modules all weigh less than 200 pounds.... There would be more modules, they would be smaller, and lighter, and there would be more joists too, but probably only double-sistered, not triple-sistered. Not too much work, if you want to go that way.

The sentiment was that it will be cheaper and quicker to do their plan.
Hmmmm.... Color me skeptical! I'm not so convinced... What is their plan for the joists, then? We are still spanning 16 feet with a heavy load, and deflection can't be more than L/360... plus there needs to be a margin for other heavy things you might need to hang form the ceiling, such as clouds, lights, diffusers, other acoustic treatment.... So plenty of extra dead load and live load capacity needed...

I'd talk to them again, mention doing smaller modules and using drywall lifters....

- Stuart -



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Re: New Studio Build Underway

#42

Postby howiedrum » Fri, 2020-Jan-10, 03:42

Did you show him this thread? viewtopic.php?f=12&t=50
I didn't know about this thread on inside out ceilings. I did share with the builder all of the photos in this thread from other posts you had done, but not the very nice write up you did. I will make a copy and share with him tomorrow.

More drama has occurred since my last post. It's exhausting. The day after New Years day, Wednesday Jan. 2, the builder and his two co-workers only worked in the morning on this beautiful sunny day. Then no one showed up on Thursday and Friday. I texted the builder and didn't hear back, which was odd. The general contractor called me on Saturday and told me that his builder had some "personal issues" come up and that he was going to be fired if he didn't work them out by Tuesday. Well he didn't, so he was let go. Then another long time employee quit. So nothing got done this week. Another builder has been assigned my job and I will meet with him in the morning.

What happened next I am not even sure I can explain clearly. The general contractor called and said (I am para-phrasing) that he found a plan that has a dated/stamped approval on it that is significantly different than the approved plan, with much less materials on it. He asked if it's possibly he picked up a different plan from the printers than what I had made for him. The only way this could have happened was if he never picked up an earlier plan in April 2019 and then was given that instead of my final approved plan. But how could it have the correct stamped date on it. He is going to show me this tomorrow. So he is going to try to convince me that this is the plan he was bidding (in his head) and then try to get more money from me. I hope no one else has to go through this bullshit. It's crazy.



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Re: New Studio Build Underway

#43

Postby Soundman2020 » Fri, 2020-Jan-10, 12:07

What a saga and run-around they are giving you! Man, that sucks. It looks like they are trying to weasel their way out of complying with the agreement. I'd spread the word locally that this company is NOT a good choice, they they are doing a lousy job on your place, and that you do NOT recommend them, under any circumstances.

When you meet with the guy, I'd hit him with the argument that, if he is working from that plan with LESS materials on it, then why did they install MORE materials, and the WRONG ones at that, in several places, without written approval from you? For example, why did they use 2x12 engineered joists, when 2x8s were on the plan, and at best 2x10s could have been used? Why did they make them 16" OC when the approved plan calls for 24" OC? That's an increase of 30% in materials, right there, just from the wrong spacing.

His argument is not consistent: If they are using other plans, then why are they not following EITHER of the plans? I'd threaten that, if he wants to stick to the plans rigidly, then he'll have to tear down everything he has already built (at his expense), then re-build it (also at his expense). Either that, or just stick to the approved plans and stop arguing.

Also, if he's using the "less materials" plan, then tell him you want your 10 k back! You paid that precisely in order to cover the extra materials that he said he didn't include... Perhaps it's time to get a little more hard-nosed. Maybe also tell him that you expect to be compensated financially for the week of lost building time, since you have deadlines to meet for having the building up.... And also tell him that you'll be inspecting every tiny detail from now on, every day, and rejecting whatever does not exactly meet the approved plans, even if it is off by only 1/8". If he wants to get snarky and nit-picking, looking for loopholes, then you should get doubly so. It's not pleasant when it comes to this situation, but it seems to me that it is warranted, since they clearly don't want to do the job right, and are looking for any excuse to avoid meeting their obligations.

- Stuart -



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Re: New Studio Build Underway

#44

Postby howiedrum » Fri, 2020-Jan-10, 22:12

Why did they make them 16" OC when the approved plan calls for 24" OC?
To be fair, the approved plan didn't state 24"OC. We talked about the 2x12 joists and he admitted that the builder made a mistake and they should've been 24"OC. He insisted that 2x8s alone would not suffice the 18' span though. He said as a general rule of thumb a 2x4 can span 4', a 2x6 spans 6', a 2x8 spans 8' etc. but you can go a little extra. He said if you go strictly with the minimum allowable on the span tables, that you often get some sagging. He used the example of walking on second story homes and feeling the floor move a bit. The original plan was to use 2x8s and sistered 2x8s to support the silencer boxes. But he felt that wouldn't be stable enough and it would require specific engineering to pass inspection. For those reasons he went with the 2x12s. It's done, so I will live with it.

I have a question regarding the sound isolation loss and extra treatment I will have to do. Is that because of the 16"OC or the 2x12s or both?

In my meeting with the contractor he didn't bring the other plan and he did not ask for any extra money. I shared with him Stuarts inside -out module plan and his idea was sort of a compromise. He would apply the OSB, GG, drywall at the ends first and continue towards the middle using scaffolding and then build two modules for the final sealing of the ceiling per Stuarts plan. So it wouldn't be necessary for someone to work laying down in that 18" gap.

Another question. Have you heard of or experienced any damage to the drywall occurring on top of the OSB on the middle leaf/attic floor from workers walking on it when installing the HVAC or insulation or other reasons for walking inside there? This was concern for the new builder.

Final question: The former builder's plan for the exterior wall sheathing was to tack on the OSB using 8d nails with caulk on studs (already done), then green glue, then 2nd layer of OSB using 16d size nails to go through both sheets of OSB into studs. The contractor thought it would be better to not just tack on the first layer, but to fully nail down it using 8d size nails, then 8d size for 2nd layer of OSB. Which would you recommend?

Monday they will begin working on the roof. Things are moving forward. The general contractor is actually going to put his tool belt on and help with the roof due to the number of employees he recently lost and his budget concerns.

Thanks!

Howie



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Re: New Studio Build Underway

#45

Postby Soundman2020 » Sat, 2020-Jan-11, 03:20

Glad to hear that things are still moving! Despite the problems, at least there is some advance happening.

Another question. Have you heard of or experienced any damage to the drywall occurring on top of the OSB on the middle leaf/attic floor from workers walking on it when installing the HVAC or insulation or other reasons for walking inside there? This was concern for the new builder.
That's why the HVAC goes in BEFORE the ceiling is done... :) Nobody walks on that ceiling, ever, so it has no additional live load: only dead load. Perhaps that's why he's so confused about the span handling capabilities of various lumber sizes! He's thinking that it will have to handle the live load of people and furniture on it, as though it were a true attic, which is why he brought up the example of the "old floor" sagging and bending as people walk on it... but nobody walks on the middle-leaf ceiling OR the inner-leaf ceiling.

If he thinks that the HVAC guy needs a surface to stand on for installation and maintenance, then you could put some plywood sheets up there, on top of the drywall, in the area around where the plenums will be, but the area where the AHU, dampers, intake vent and exhaust vent will b,e does not have any middle-leaf ceiling below it: All of that is directly over the lobby and bathroom, where there is no middle-leaf ceiling. I designed it that way specifically so there is plenty of access for HVAC maintenance / repairs / replacement for the parts that need access. Parts of the plenums and ducts are over the middle-leaf, yes, but after the system is installed they should not need touching again, and even if they do need access, it would be simple to slide in some plywood over the drywall temporarily, to protect it, then remove it when the work is done (or leave it permanently, if you prefer! :) ). However, it's rather unlikely that it would be necessary to access those regularly.

Also, don't forget there is access into the attic space from the large air air vents in the gable end. That one is sized large enough that you could even fit the entire AHU through it, from the outside of the building (using scaffolding, of course), without needing any access from the inside. For example, if the entire unit failed completely, then that would be a relatively easy way to get out and replace it.

Getting back to your GC: He's also not correct about his "rule of thumb" for how much a given lumber size can span: you have to take into account the SPECIES of wood, the dead load, the live load, the deflection factor, whether it is notched or not, whether or not it is exposed to water, and whether it is a floor joist or a ceiling joist. As I implied above, floor joists must carry live loads, ceiling joists do not. Some species of wood can carry much larger loads than others. Some types of lumber are specifically designated as "structural", able to carry a larger load. The others are not. It seems to me that he's not very knowledgeable about wood properties and spans! His "rules of thumb" are not very valid at all.

He's also not reading the plans correctly! either that or the plans he has are not taken from the ones I did for you, because on the design I did originally, those are 2x10 joists, not 2x8! I'm not sure where he got the idea they are 2x8. Both the middle-leaf joists and also the inner-leaf sistered joists are all 2x10. There's no 2x8s in there. The rafters and rim joists are 2x8, yes, but the joists are all 2x10.

In fact, those distances COULD be spanned using 2x8s at 16"OC (barely), but I opted for 2x10 24"OC for several reasons (including an extra safety margin and also improved isolation at low frequencies) .... however, instead of using either of those, 2x8 16" OC, or 2x10 24" OC, instead, he built it as 2x12 16" OC!!! :roll: That's strong enough to park a truck on!... So it's overkill, and expensive.

To be fair, the approved plan didn't state 24"OC.
Ooops! Then the architect screwed up! Because the original design has 2x10s spaced 24" OC...

He said as a general rule of thumb a 2x4 can span 4', a 2x6 spans 6', a 2x8 spans 8' etc. but you can go a little extra.
Ummm.... :) Carrying what load? And what species of wood? And what deflection? :) Those are key points to any discussion of how far a given piece of lumber can safely span. In fact, according to the American Wood Council's span calculator, ANY 2x4 of ANY wood species and ANY structural grade, can easily span 8 feet (not 4 feet, like he said) at 16" OC with a dead load of 10 psf PLUS a live load of 10 psf (assuming deflection of L/360). Most species can span 9 feet like that, and some can even span 10 feet. I have no idea where he got his rule of thumb from that 2x4's can only span 4 feet, and 2x8s can only span 8 feet. That's like saying that if a vehicle has two wheels it can carry two people, if it has 4 wheels it can carry 4 people, and if it has 8 wheels it can carry 8 people.... Easy to remember, sure, but totally wrong, and just plain silly.

According to the same span calculator, for the case of 2x8 joists, ALL species of wood with just one single exception (Norther White Cedar) can span 16 feet with the same factors as above, and in fact in some cases even 2x6s can span that distance. Which shoots down his other rule of thumb, that a 2x8 can only span 8 feet. In fact, according to the same source, most 2x8s can span 18 feet, and a few species can even handle 20 feet. So, considering that your span is 17 feet, it actually would have been possible to use 2x8s... assuming certain wood species. But I didn't do that; I always prefer to go one size bigger for safety, which is why I put 2x10s in the original design. In theory, they could span 22 feet (far more than your 17 feet). The 2x10s at 24" OC in the original design could in fact carry more than twice the load that they will actually be carrying. But the 2x12 monsters that they actually put in, can carry about SIX TIMES times the load... it could carry a live load of about 31,000 pounds, according to the span calculator... (that's live load, in addition to the dead load! Like I said, you could park a truck on there. That's about enough capacity to carry an entire 18-wheeler big rig... :shock: So yeah, I'd call it "slight overkill" for your middle.leaf ceiling... :)

It's a great idea to include a margin for safety, absolutely, but I think having enough capacity in your ceiling to hold a big rig, is going just a little overboard. :)

Anyway, it's done now, and you can't go back. It certainly won't do any harm, structurally, but it sure did cost a lot more than was necessary. The only harm here is a possible slight reduction in isolation for very low frequencies, due to going 16" OC instead of 24" OC. If you are concerned about that, then you could add more mass to the deck on that middle-leaf, by increasing the thickness of the plywood deck to 3/4", and/or switching to OSB, instead of plywood. OSB is a little more dense than plywood (around 610 kg/m3 vs. 560 kg/m3), so you'd get 9% more mass (not much!) just by switching to OSB, and another 18% by increasing the thickness. Between those two, you'd be increasing the mass of that layer by nearly 30%, which is plenty to offset the reduced isolation. Another option would be to use Green Glue between the two layers: that would give you a substantial increase, but it won't be cheap, as there's over 400 square feet of deck to cover. So if you are concerned about isolation, then those would be the options.

I have a question regarding the sound isolation loss and extra treatment I will have to do. Is that because of the 16"OC or the 2x12s or both?
The spacing is the issue. The joists don't really matter at all here (except for the cost!) With wider joist spacing, there is more free area of sheathing in between, so it is able to flex more. It gets complicated, but that's basically the issue.

Final question: The former builder's plan for the exterior wall sheathing was to tack on the OSB using 8d nails with caulk on studs (already done), then green glue, then 2nd layer of OSB using 16d size nails to go through both sheets of OSB into studs. The contractor thought it would be better to not just tack on the first layer, but to fully nail down it using 8d size nails, then 8d size for 2nd layer of OSB. Which would you recommend?
The nails on the second layer need to fully penetrate into the studs, just like the nails form the first layer. Thus, they need to be at least 3/4" longer if the first layer is 3/4", or 5/8" longer if it is 5/8". Normally I use half schedule on the first layer then full schedule on the second layer. That means the the first layer actually gets one and a half schedule, and that's fine! But the second layer does need a full schedule in order to comply with code, and for the same reason, the nails need to penetrate into the studs properly. So whatever your local code requires as the nailing schedule, use half of that on the first layer by itself, then all of it on the second layer. And do try to stagger the nails a bit! In other words, move the nails by a couple of inches on the second layer, to ensure that those nails don't hit nails that are already there on the first layer!

Monday they will begin working on the roof. Things are moving forward. The general contractor is actually going to put his tool belt on and help with the roof due to the number of employees he recently lost and his budget concerns.
Cool! :thu: Don't forget to take your camera, and take plenty of photos to document everything that is happening! And post a few of the best ones here... :)


- Stuart -




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