Rod's Super Door 4731 Seals - Clearance on Hinge Side?

[Wayne Rose]

Hi,

This is my first post on this forum, so I will try my best to follow the rules, before I ask my question(s).

1. Reviewed the Reference Area. Excellent resource, thanks.

2. Searched for similar topics. Thanks to Mr. Gervais for his detailed explanation of how to install and tweak 4731 (K trunk rubber) door seals. Rod had responded to a question similar to mine, regarding compensation spacing, on another forum, but the link to that thread no longer works.

3. I've included my location in my Profile. I'm in Whitby, Ontario, Canada, near Toronto.

4. Overview: I'm no expert. This is the third room I've built. This one is a small, rectangular (18' x 11' x 7') free-lance, music writing/production room. Construction is finished, except for the doors, cork laminate floor, paint, trim, and lighting fixtures. I realize there are severe limitations to this type of room, compared to a professional recording studio. However, I expect it will work quite well for my needs.

5. I rarely if ever perform. I don't have a band. I work mostly in-the-box, but will likely record individual musicians or small ensembles from time to time. I tend to work around 85dB. Occasionally louder. Rarely, if ever, do I expect to record a full drum kit.

6. Construction details:
Due to space limitations my walls are single stud:
gypsum | gypsum | stud w/ FG Pink | RISC clips w/ HC | gypsum | GG | gypsum.
Base plates are mounted on rubber pads, and fastened to the cement floor using Tapcon screws and rubber/steel isolation washers. Top plates are fastened to joists using the same type of isolation washers.
I used 1/2" Firecode drywall, instead of 5/8", because the density is similar and overall TL is slightly better according to NRC-FR761. I don't think anything about my room is optimal. Everything was a compromise.
I installed two layers of drywall against the sub-floor up between the joists. I checked the engineering specs in detail, and my 2 x 10 (1 1/2" x 9 1/4") joists can handle the dead load easily.
Beneath that, 5 1/2" of Roxul, then RISC clips w/ HC, Green Glue and double drywall, like the walls.
I spent a good six months sealing absolutely every flanking path I could find. It takes a long time, because you have to really think about every detail, and find unique solutions that do the job. My wife can run the vacuum back and forth across the hardwood floor upstairs and you can't hear it. So far so good.

7. I installed a decoupled floor system following Rod's directions on pg269 of his book. I have studied vibrating plates some, and believe I have done it correctly. I use a single Dynaudio sub-woofer, which extends to 18 Hz, which I will mount on a Durometer 30 rubber pad. We'll have to see how well that works.

8. There are no non-parallel features of the room, but the room is asymmetrical. There is a 6' x 4' closet (specific application TBD) containing the electrical sub-panel (IG wiring, by the way), also double drywall construction, on the right side wall, about three feet from the front of the room. That's where one of the two doors will go. From what I've read, the jury is still out on the asymmetrical question, but I'd like the door and seals to be as good as the existing wall, if at all possible.

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12. No pictures or links. Will post as they become relevant.

13. Questions: See bottom of following post.

14. My budget was $20K including acoustic treatment. Will exceed that by >10% by the time all is said and done.

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Thanks for the opportunity to take part in this excellent forum. This is quite long, so I'll post my door question(s) in the reply below.

[Wayne Rose]

Hi, I'm back!

I'm in the process of building two Super Doors. I'm planning to start by installing 1 3/4" solid core wood doors, in 1 1/4" jambs (from 6/4 stock, it just worked out that way) with 4731 '54 Chevy rubber seals on 3/4" stops (from 4/4 stock), and Zero International 568A thresholds.

Once I've had a chance to test these for a while, I plan to finish them by adding lead sheet and 3/4" Baltic birch plywood or possibly Extira, plus additional seals and automatic door bottoms from Zero.

Pull handles and closers are de facto for me. Not sure about the deadbolt idea.

Not having used the 4731 seals before, I'm concerned about the compensation spacing (reveal gap), especially on the hinge side. I don't want the door to bind on the seal while it's being closed.

Thanks again Mr. Gervais for your step-by-step explanation of how to install these seals, elsewhere on this forum. My questions here are related only to reveal gap and hinge type.

The larger of the two doors (32" x 80") will weigh about 250 lbs. The smaller (closet described above) is 30" x 80", and closer to 200 lbs. Stanley (and other manufactures) spec 3 medium weight 4 1/2" hinges for this size and weight of door. Zero Int'l specs 4 hinges. Rod spec's 4 in his book as well.

I asked the guys at Zero why 4 hinges, and got a somewhat vague answer about the door swinging smoothly.

I'll use ball bearing hinges, for sure, but I'm not sure about the hinge weight (see Q1 below).

As far as I've been able to find online, the gap between closed hinge leafs on a standard swaged hinge is 1/16". On a flatback (unswaged) hinge, it's about 5/32". The door will need to open 180deg.

I've been considering using a 3/16" gap (reveal) around the door, which was a suggestion I got from that other studio construction forum I mentioned above.

As you can see, I've researched the topic already. Probably over-researched it. Here are my questions:

Q1: What kind of difference would hinge weight (leaf thickness), standard (.134") or heavy (.180"), make in deciding on the number of hinges, i.e., what do I really need?

Or same question, from a different angle: Is two ball bearing knuckles enough (standard), or are 4 required (heavy)?

Q2: Would a full-mortise flatback hinge be best? Or is there another type you'd recommend that would give me the required gap? Fine home building experts suggest bending the hinge leafs at the knuckle to increase the gap, but I've destroyed hinges before by trying that - it weakens the hinge.

Q3: The hinge backset will also partially determine the angle at which the door edge strikes the seal. Is the standard 1/4" backset enough, or should I allow more?

Any helpful advice from anyone with experience installing this type of door, seal and hinges would be greatly appreciated.

Kind regards,

Wayne

[Wayne Rose]

It's been a couple of weeks, and no responses to my questions, so far. However I have continued to explore the issue elsewhere, and have some feedback, in case it might be of help to others.

Q1: What kind of difference would hinge weight (leaf thickness), standard (.134") or heavy (.180" thick), make in deciding on the number of hinges, i.e., what do I really need?

Or same question, from a different angle: Is two ball bearing knuckles enough (standard), or are 4 required (heavy)?

I spoke with a rep from Stanley's Commercial Hinge division, who was very knowledgeable and was able to visualize the super door construction easily by telephone. Her concern was that the hinge size for the bearing layer (the 1 3/4" solid core door) would be limited by its thickness, causing the sandwich structure (after adding the lead and plywood/Extira layers) to be "back weighted", with the effect that the door would want to twist on its hinges.

For this reason, she suggested four heavy (.180"), 4 ball bearing knuckle hinges. Normally, the hinge spacing for four hinges would be one hinge 5" from the top and one 11" from the bottom, with the other two evenly spaced between them. In this case, however, she suggested moving the uppermost center hinge closer to the top, as the top hinges bear most of the torque.

Q2: Would a full-mortise flatback hinge be best? Or is there another type you'd recommend that would give me the required gap?

The Stanley rep understood my reasoning in thinking a 3/16" reveal gap might be better, but pointed out that unswaged hinges are only sold as custom order, and would be very expensive for this size and weight.

Even stock heavy, four bearing hinges are not cheap. I did manage to source a reasonably priced lot of used hinges of the right type online. They were delivered yesterday, and should do fine.

In the interim, I've been examining exterior doors to see how they are hinged and set. Turns out many have a 1/16" wide rabbet (slightly wider along the hinge side, to accommodate the thicker seal there), depth equal to the hinge backset, around the upper three closing edges of the door. I could set the door with a 3/16" reveal gap, by routing a similar rabbet along the hinge side, to allow setting the K seals a little deeper, using Rod's technique to ensure a tight seal without binding.

What I still need to hear from ye who are more knowledgeable is do you think this approach will work, or am I just blowing smoke?

Q3: The hinge backset will also partially determine the angle at which the door edge strikes the seal. Is the standard 1/4" backset enough, or should I allow more?

This question turns out to be irrelevant, after talking to the Stanley rep, because the maximum hinge bearing surface on the bearing layer will be required.

Hope this monologue has been helpful for some. I'd still like to hear thoughts and advice from those in the know though.

Thanks for reading.

[Soundman2020]

Wow! Not sure how I missed this thread! I just found it again by accident...

I'm in the process of building two Super Doors

Since you don't seem to have the need for very high isolation, is that absolutely necessary? You've done a pretty good job so far of isolating the room, but a pair of superdoors might be overkill.

Not having used the 4731 seals before, I'm concerned about the compensation spacing (reveal gap), especially on the hinge side. I don't want the door to bind on the seal while it's being closed.

If the worst comes to the worst, you can always take off the seals, rabbet the jamb and/or door edge a bit with a router, and put the seals back on again. The idea is that they need to be slightly compressed, but only to about 15% or 20% of their nominal thickness, max.

Rod spec's 4 in his book as well.

I agree with Rod, for sure. The manufacturers are probably giving you the minimum that would work, but for a heavy door like that, I'd like to have some insurance in place. An extra hinge means that each of the others is carrying 25% less load than it was, and therefor much less likely to fail or sag.

The door will need to open 180deg.

? Are you SURE about that? Most doors only need to open 90°, or a bit more. at 180°, it will be up flat against the wall: why does it need to open so much? Does it open into a corridor of some type, where it would be entirely blocking the passage if it did not open that much?

Q1: What kind of difference would hinge weight (leaf thickness), standard (.134") or heavy (.180"), make in deciding on the number of hinges, i.e., what do I really need?

Go with the heaviest duty hinges you can find that will fit your door and do the job, and use four of them: two towards the top, one in the middle, and one towards the bottom. There's no problem with over-rating your hinges: the door is very heavy, there are lots of stresses going on in the hinges every time you open and close it, and you do not want it sagging, warping, or twisting over time as that would wreck your seal. The manufacturers are telling you which of their hinges will be able to carry the weight, but they likely are not concerned about slight sagging over time as that would not be an issue with a non-studio door. You have a special situation, since seals are critical for your doors, in order to keep the isolation. Go with the heftiest hinges you can find (within reason!).

- Stuart -