Stage Floor Replacement

[VeeDubTDI]

Well, it's finally finally happening. We're getting a new floor to replace our worn out, 19 year old, heavily used tongue and groove floor.

The new floor will be two layers of plywood on top of the plywood underlayment that's on top of the sleepers (3 layers total), with the top surface being A grade and painted black.

Here are some pics to feast your eyes upon. Sorry for the crappy cell-phone quality of some of them. Others aren't so bad.

Click to make the images full-size. I'll be posting more as the project progresses.

[VeeDubTDI]

As you can see, the pit covers downstage are not getting replaced. They're in good shape, and we will just sand them down and paint them black.

[Footer]

No Maso? ???

[DaveySimps]

I agree, why not Masonite as a top layer? I just checked my local pricing. I can get 3/4" Masonite cheaper than 3/4" grade A ply. Plus, it is a better surface for theatre in general. Just curious.

~Dave

[derekleffew]

It may be too late, but if it were me, I'd get those soft goods off the floor and bagged/wrapped with Visqueen ASAP! I agree that the top surface should not be painted pine plywood. I've only used Masonite in 1/4" and 1/8" thinknesses, and would agree that's a better top layer.

Do you intend to permit screwing on your new stage?

[Van]

.....
Do you intend to permit screwing on your new stage?

I'm a huge fan of 1/4" MDF as opposed to Masonite. It tends not to buckle as much. 'Course there's nothing that say you can't always go in and lay a layer of MDF over the top layer of ply as a prophylatic measure.......

[derekleffew]

...of 1/4" MDF as opposed to Masonite. ...

What's the difference? Isn't MDF the same as untempered Maso? And while were on the subject, since Masonite no longer manufactures sheet goods, what's the new version actually called? HDF? Should the glossary entry be edited?

Another gem of wisdom that Van previously liked: Prime all six surfaces of any pressed-fiber sheetgood before laying.

[SteveB]

'Course there's nothing that say you can't always go in and lay a layer of MDF over the top layer of ply as a prophylatic measure.......

Unless the planned layer is flush with doors, entry way, etc... Not to mention pit limits needing to be reset. Adding even a 1/4" layer sometimes throw's everything off.

Steve B.

[MillburyAuditorium]

Congrats on the new stage :D Ours needs a good sanding To many dance academy's using the wrong tape :P

Quick question for anyone, How come some theatres paint the stage black? I prefer the glossy brownish look myself. Does it do something to the lighting? Or is it just prefernece?

[Van]

What's the difference? Isn't MDF the same as untempered Maso? And while were on the subject, since Masonite no longer manufactures sheet goods, what's the new version actually called? HDF? Should the glossary entry be edited?
....

I'm glad you asked. MDF or Medium Density Fiber board is made of much finer fibers, actually much more like dust. The entire sheet is impregnated with resins then press molded resulting in six sides that have the same smooth texture. When you cut through MDF the new edges have the same dense smooth edges. Masonite or Tempered Hard board is much more of a paper product. The difference in the fibers making up these two similar yet different engineered lumber products is readily evident. Masonite fibers tend to be coarser and are much more loosely packed. Masonite or tempered hardboard comes in two varieties ; single and dual sided tempering. The tempered side is the slick side, you'll notice that the back side of single sided tempered masonite has a weird textured side this is the result of the manufacturing process which is similar to hand made paper, if you've ever done that, the resultant paper has a smooth-ish top and the backside of the paper takes on the texture of the screen.

One of the main reasons I prefer MDF over Hard Board is the uniform distribution of the resins throughout the product. MDF is much more moisture resistant and therefore much less likely to buckle and therefore requires far fewer screws to secure it to a floor. Lastly MDF tends to be more more uniform in thickness than Hardboard While I do prefer MDF it is wise to take several precautions when doing extensive work with it;
The resultant dust is much finer and therefore tends to get everywhere.

There is a MUCH higher Formaldehyde content in MDF and it is strongly recommended that a dust mask or respirator be worn when working it.

MDF, because of it's higher density, can tend to dull blades a little quicker than other engineered lumber products.

MDF tends to give friction burns much more easily than Masonite, be careful when maneuvering a large sheet as simply sliding your hand to reposition your grip can result in painful burns.

[VeeDubTDI]

Well, the decision for no Maso was based, in part, on the information from a number of consultants. Ultimately, we think that the plywood will hold up better than the maso in our situation. This space sees a lot of heavy use, and we're trying to keep maintenance to a minimum, even if the surface isn't as nice. Especially with the large number of tap groups that we get, the edges of the maso would start to fray and get soft, making the surface uneven.

At this point, we can't add maso to the top of it because it would change the height of the stage when compared to the concrete off-stage rooms and the backstage hallway. If the plywood ends up not working out very well, we can always change the top layer to maso in the future.

This is a state job, so we're locked into it now. We can make changes in the future, but not right now. So, we'll see how things go.

As for the soft goods, we're replacing all of the legs and teasers in the near future. The project is going out to bid soon. I'm not terribly concerned about them at the moment. If they were new, I would have taken them down and stored them properly.

So all in all, this is a big project that needed doing, and we'll continue to play it by ear. At this point, the current plan is leaps and bounds above what we had before.

[VeeDubTDI]

Pics from yesterday and today...



After it's all drying and such, we're going to paint it with "Deck Paint" stage floor paint.

[mstaylor]

I will be interested in how the finish looks after staining it with the screw heads being spot patched. I woud think it would be splotchy. It may be better to field patch the playwood and paint it instead of staining it.

[VeeDubTDI]

Can't see the patch marks at all. They patched, sanded, stained, patched, sanded, stained, and stained again. The finish looks very even... just the slightest hint of roller marks before it was totally dry, and those were only visible from certain angles. I'll see what it looks like tomorrow.

[VeeDubTDI]

pics from today...

[teqniqal]

A bit of history: "Back in the day" when Masonite Corporation made tempered pressboard, they used to sell a product called "Duron WR". This was super-dense hardboard product that was Water Repellent. It made great stage flooring. Alas, 'tis no more.

However, Sierra Pine now makes two products that are roughly the same as Duron WR. If you contact them they will send you samples to test for workability (no, you won't get a 4'x8' sheet of wood in the mail...). A bonus is that these are formaldehyde-free products.

The Medite FR product information can be found at:
(http://www.sierrapine.com/index.php?pid=79)

The Medite II product information can be found at:
(http://www.sierrapine.com/index.php?pid=67)

The Medite II is not Fire Retardant, but it is stronger and absorbs less moisture, so it may be a better solution for the abuse that stage flooring receives. To make it more suitable for stage use the Medite II could be treated with an intumescent paint like:
* NoBurn” (http://noburn.com/)
* “FlameStop” (http://www.flamestop.com/)
* “FireFree88” (http://www.firefree.com/ff88.php)
* “PaintToProtect” (http://www.painttoprotect.com/)
* PPG “SpeedHide” (http://corporateportal.ppg.com/NA/PAF/PMC/Brands/FPC/400_Intumescent/)
* Contego “Fire Barrier” (http://www.contegointernational.com/)

We should all be using intumescent paint for anything that comes onto the stage. Depending upon the product, it can come in a color, or be tinted to match a color. Also of interest is the videos on some of these product web sites that show "with" and "without" comparisons of structure burn rates (some with, and some without, accelerants, too.)

One of the reasons generic "masonite" doesn't last too long on a stage floor, and the same reason that soft pine and plywood floors deteriorate rapidly, is because they are not dense enough to withstand the point loads that piano casters, cable crates, and ladders present to the surface.

Generic "masonite" is a soft material technically known as Class 0 Hardboard. This is all they stock at most lumber stores. If you want a tougher product you usually have to special order it. Hardboard is available in 5 Classes (0-4), and it is the class 3 and 4 products that are typically more appropriate for use on stage floors.

A second consideration is the means of attaching the hardboard/MDF to the subflooring. You must countersink the screw holes before you screw the deck down. The high density of the Class 3 or 4 hardboard/MDF doesn't allow it to just mash out of the way like plywood.

Also of great concern is the resilience of the floor with regard to dancers. ESTA has developed recommendations for sprung floors to reduce the likelihood of joint injuries. An unyielding floor is not good. Not that this doesn't mean that the floor is locally spongy, but instead that the floor is monolithically spongy - very much like a Basketball Court floor (and for the same reasons).

[derekleffew]

Can't see the patch marks at all. They patched, sanded, stained, patched, sanded, stained, and stained again. ...

I'm curious as to what they used to cover the screwheads. It looks like drywall joint compound, but I'm thinking maybe auto body filler (Bondo)?

[TimmyP1955]

I'm glad you asked. MDF or Medium Density Fiber board is made of much finer fibers, actually much more like dust. The entire sheet is impregnated with resins then press molded resulting in six sides that have the same smooth texture. When you cut through MDF the new edges have the same dense smooth edges. Masonite or Tempered Hard board is much more of a paper product. The difference in the fibers making up these two similar yet different engineered lumber products is readily evident. Masonite fibers tend to be coarser and are much more loosely packed. Masonite or tempered hardboard comes in two varieties ; single and dual sided tempering. The tempered side is the slick side, you'll notice that the back side of single sided tempered masonite has a weird textured side this is the result of the manufacturing process which is similar to hand made paper, if you've ever done that, the resultant paper has a smooth-ish top and the backside of the paper takes on the texture of the screen.

One of the main reasons I prefer MDF over Hard Board is the uniform distribution of the resins throughout the product. MDF is much more moisture resistant and therefore much less likely to buckle and therefore requires far fewer screws to secure it to a floor. Lastly MDF tends to be more more uniform in thickness than Hardboard While I do prefer MDF it is wise to take several precautions when doing extensive work with it;
The resultant dust is much finer and therefore tends to get everywhere.

There is a MUCH higher Formaldehyde content in MDF and it is strongly recommended that a dust mask or respirator be worn when working it.

MDF, because of it's higher density, can tend to dull blades a little quicker than other engineered lumber products.

MDF tends to give friction burns much more easily than Masonite, be careful when maneuvering a large sheet as simply sliding your hand to reposition your grip can result in painful burns.

With the materials I've seen, I would have reversed the descriptions. The MDF I have seen, when compromised, will pull apart in layers like cerial box material.

[ruinexplorer]

Well, the decision for no Maso was based, in part, on the information from a number of consultants. <snip> Especially with the large number of tap groups that we get, the edges of the maso would start to fray and get soft, making the surface uneven.

Wow, I would have thought that you would have wanted to stay with TnG if you have a large number of tap groups. If they are professionals, they usually prefer hardwood to plywood. Of course, that would have been more expensive.

Personally I hate stages with Maso floors.

[DramaTeach]

Hey Guys!

I work at a public high school near Chicago and have finally convinced folks that we need to do something about our stage floor.

Here's the issue: for years we were unable to paint, drill into, build on the "beautiful" hardwood floor. However, after years of plays being performed on the stage, it was inevitable it would fall into disrepair. Currently the hardwood (I'm not sure what the wood is) is buckling in places. They are going to fix that and replace the front facing of the stage.

Here's part of an e-mail I got today:

What I want to do is put a layer of plywood down over the floor and then install a layer of melamine (like that of most Stages).

My question is: is this going to be the wisest choice for staging top? We do two major productions a year on the stage and then a bunch of band concerts, choir concerts, miscellaneous performances.

Thanks!

[Footer]

Nope. That stuff used to be used but has long since been replaced my painted masonite. Have them fix the floor and then just throw maso down over the floor. Unless they want to have to deal with having a bump up at every doorway that is at least and inch...

[DramaTeach]

Thanks! That's what I had assumed, but I wasn't certain. I'll pass that along.

[ruinexplorer]

Personally, I prefer hardwood flooring. Sure, you end up with issues from time to time, but if treated right (stained, not painted), I find it superior. Depending on what your additional events are, many musicians will also prefer the hardwood for its accoustic properties. I don't like how hardboard deteriorates, no matter how inexpensive it is to replace.

I look at it like the difference between a KIA and a BMW. Sure the KIA is cheap and does essentially the same job, but it will most likely have more parts to replace and will have a shorter life than the BMW. With the BMW, you will want to drive it a little easier because of your initial investment, but treat it right and it will last a lifetime.

[Morydd]

I see it as the difference between a KIA and a BMW too, but I go with the KIA. Sure, if you treat it right the BMW will last forever, but if you want to be able to throw tools in the trunk, occasionally cram some lumber inside, park in sketchy parts of town, and not go broke in the process, the KIA is the better option. We paint our floor. We screw scenery to the floor. Drill holes for cane bolts, tap dance, tape and otherwise abuse the floor. And we know that we can replace that top layer when it gets bad without it being a giant construction project. Most of the time another coat of matte black paint is all that's needed.

[teqniqal]

My question is: is this going to be the wisest choice for staging top? We do two major productions a year on the stage and then a bunch of band concerts, choir concerts, miscellaneous performances.

One of the most important questions to ask / research, is how the original floor was constructed. If it was fairly recent, then the original Architectural plans should show a detail and / or have a written specification. This will show / tell you if the floor was sprung (good) or if it was just laid on top of the concrete (bad).

If the building documents are not available, then you can sometimes find a place on the stage where there is a floor box cover or other element that can be removed to let you see down in a crack how many layers of whatever are there. If all else fails, investing the time and money to do an exploratory demolition of a small area is a worthwhile effort. You have to know what you are starting with.

If the floor is sprung, then the issue of just adding a sacrificial top skin is fairly easily resolved, however, if the floor is not sprung, then it would be irresponsible to cover-up 'wrong' with a fresh layer of 'wrong'. Injuries to performers due to working on hard (unsprung) floors is a well-documented issue, and to ignore this fact could expose the school to future litigation should injuries occur.

The necessity of springing the floor is not too dissimilar from the justification for providing sprung floor in gymnasiums (albeit, the spring characteristics are NOT the same for sports and dancing / acting). The injuries to joints and bones are commonly discussed throughout the industry, however, dancers will tell you that the constant pounding of your jaws during repeated vertical motion can clatter your teeth together and chip or wear the enamel veneer off of them - a sprung floor can provide a significant reduction of pain in this area.

Another good argument against hardwood floors is that they are prone to developing grooves from heavy point-loads being rolled / dragged across them. These grooves can develop broken wood edges that can introduce very long splinters into dancers feet and other body parts that might slide across the floor (Yikes! That hurts just writing that sentence!). A hardwood floor requires much more vigilance (maintenance) to keep them safe from splintering.

The available space between the supporting structure and the finished floor level may significantly influence the type of materials required to achieve the necessary resiliency.

Also to be noted is that current building codes are very specific about the chemical make-up of the construction materials (i.e. components containing carcinogens) and the fire retardancy of the materials used for anything that is on the stage (you should be familiar with the Iroquois Theatre Fire and how this has affected the NFPA 101 Life Safety Code). Furthermore, adding level changes that may create impediments to the movement of people and equipment is also affected by the ADA requirements in the building code.

The actual construction may, or may not, be something that you can do yourself, however, the design of the proper solution may be outside of the scope of your job responsibilities. In fact, this level of construction may even require that the documents be prepared by a licensed Architect (whom we would all hope would seek the assistance of someone qualified to assist them in the development of the construction documents.

[DuckJordan]

we actually have a pine floor at one of the spaces. gaff tape rips up splinters leaving the floor worse than if we had gone hardwood. This gets refinished once a year. So why would the suggestion of a softwood come into a theater type space?

[RickR]

we actually have a pine floor at one of the spaces. gaff tape rips up splinters leaving the floor worse than if we had gone hardwood. This gets refinished once a year. So why would the suggestion of a softwood come into a theater type space?

Softwood is traditional, mostly because all the nailing and screwing doesn't split the whole board. I too have worked where tape pulled up splinters but it was a minor issue solved with a coat of paint. MDF & hardboard are what most consultants are putting into new stages. (Concert halls are another matter.)

[venuetech]

we actually have a pine floor at one of the spaces. gaff tape rips up splinters leaving the floor worse than if we had gone hardwood. This gets refinished once a year. So why would the suggestion of a softwood come into a theater type space?

I was told years ago that a pine floor should never be "finished" or painted, it should be oiled once or twice a year. that oil would help the wood heal itself from the nail holes and stage screws put into it.
the floor we were talking about had been finnished so i never did get to see how that played out.

[BillConnerASTC]

I was told years ago that a pine floor should never be "finished" or painted, it should be oiled once or twice a year. that oil would help the wood heal itself from the nail holes and stage screws put into it.
the floor we were talking about had been finnished so i never did get to see how that played out.

Several great threads on stage floors here - glad to be able to bump this one - searching for a solution where a user recommended our usual top layer - plyron. If you haven't seen/used plyon, it has the advantages of hardboard (or maso or Masonite if you prefer) and few of the disadvantages - like dimpling or bubbling and sounding like an oil can - because it is basically plywood with the outer veneers being hardboard.
So these folks want something that is more "self-healing" which made al the pine floor comments interesting to read - with likes and dislikes almost alternating. I use to specify pine - like 30+ years ago - because that was the traditional material and it worked well - if it was harvested maybe 50 to 100 years ago - when yellow pine and similar species trees were allowed to grow slowly and become real dense and rather than get the last board foot out of the harvest, quarter sawing or rift sawing was practiced. Nothing as pretty and hard and self healing and tough as true quarter sawn southern pine for stage floors. Regrettably for us in the theater, it seems to only be attainable at really high cost. I bought some for a small home project and IIRC near $100/bd ft. Anyways, I can't help but wonder if the likes for pine is for old dense pine floors and the dislikes are for new plain sawn fast growth material.
So anyone have any new thoughts on this? I wondered how the plain A face ply painted worked out?

[Footer]

Several great threads on stage floors here - glad to be able to bump this one - searching for a solution where a user recommended our usual top layer - plyron. If you haven't seen/used plyon, it has the advantages of hardboard (or maso or Masonite if you prefer) and few of the disadvantages - like dimpling or bubbling and sounding like an oil can - because it is basically plywood with the outer veneers being hardboard.
So these folks want something that is more "self-healing" which made al the pine floor comments interesting to read - with likes and dislikes almost alternating. I use to specify pine - like 30+ years ago - because that was the traditional material and it worked well - if it was harvested maybe 50 to 100 years ago - when yellow pine and similar species trees were allowed to grow slowly and become real dense and rather than get the last board foot out of the harvest, quarter sawing or rift sawing was practiced. Nothing as pretty and hard and self healing and tough as true quarter sawn southern pine for stage floors. Regrettably for us in the theater, it seems to only be attainable at really high cost. I bought some for a small home project and IIRC near $100/bd ft. Anyways, I can't help but wonder if the likes for pine is for old dense pine floors and the dislikes are for new plain sawn fast growth material.
So anyone have any new thoughts on this? I wondered how the plain A face ply painted worked out?

Why do you spec plyron? Seems to me you get none of the benefit of Masonite or MDF. Instead you get a floor you can not flip or cheaply replace. The plyron would install faster, but does it wear better than maso?

Sent from my Galaxy Nexus using Tapatalk 2

[BillConnerASTC]

Why do you spec plyron? Seems to me you get none of the benefit of Masonite or MDF. Instead you get a floor you can not flip or cheaply replace. The plyron would install faster, but does it wear better than maso?

Sent from my Galaxy Nexus using Tapatalk 2

Wears much better and - maybe you are not use to climates with high humidity swings - but it doesn't swell like hardboard. In a high school seems to last 5 to 10 years before flipping it for another 5 to 10. And I only have to use one layer of sub-floor and a layer of plyron. And keep in mind this is all spec, bid, install by a contractor work - new build.

So a hard surface for digs and wheels, good paintability, economical, but doesn't buckle.

[lwinters630]

Hey Bill, Footer, Van, and everyone else.

It looks like our stage floor has finally hit the limit of its useful life (35 years I think). It looks like 2 1/4 x 3/4 pine over some sort of sleepers on concrete. I haven't pulled up anything to find out for sure. It is shredding, sheering, peeling (from years of paint), and splintering. In the last 3 years it has really fallen apart to the point that I don't think that paint will hold any more and is a safety issue due to the splintering.

Because it is a high school, we have lots of events overlapping which means most musical and drama sets have to be mobile so we can clear the drama play, have a band concert, reset the play and then bring in a weekend rental dance event, back to play rehearsal then the choir concert and finally dress rehearsal and opening nite for the play. You laugh, but this is why everything is on wheels or fly's or wagons.

We just finished Les Miserables with six sets of rolling stairs, barricades, 3 story buildings that roll in, tables on wheels and carts. Heck, even the choir risers and band shells are on wheels. It is no wonder that the pine stage is falling apart.

The big question is:

Do we go over the pine with 1/4" MDF? (assuming that the edges to doors and thrust/stair edge will allow it). Will that result in paneling causing the sheets to shift with the planking layer underneath?

Or do we tear it all up and start new with ????

What do you recommend for the stage floor and paint etc.

Thanks,
Larry

[Footer]

Hey Bill, Footer, Van, and everyone else.

It looks like our stage floor has finally hit the limit of its useful life (35 years I think). It looks like 2 1/4 x 3/4 pine over some sort of sleepers on concrete. I haven't pulled up anything to find out for sure. It is shredding, sheering, peeling (from years of paint), and splintering. In the last 3 years it has really fallen apart to the point that I don't think that paint will hold any more and is a safety issue due to the splintering.

Because it is a high school, we have lots of events overlapping which means most musical and drama sets have to be mobile so we can clear the drama play, have a band concert, reset the play and then bring in a weekend rental dance event, back to play rehearsal then the choir concert and finally dress rehearsal and opening nite for the play. You laugh, but this is why everything is on wheels or fly's or wagons.

We just finished Les Miserables with six sets of rolling stairs, barricades, 3 story buildings that roll in, tables on wheels and carts. Heck, even the choir risers and band shells are on wheels. It is no wonder that the pine stage is falling apart.

The big question is:

Do we go over the pine with 1/4" MDF? (assuming that the edges to doors and thrust/stair edge will allow it). Will that result in paneling causing the sheets to shift with the planking layer underneath?

Or do we tear it all up and start new with ????

What do you recommend for the stage floor and paint etc.

Thanks,
Larry

If you don't have a solid surface to secure the maso or MDF to, your going to just add insult to injury. If the floor is as bad as it sounds, your going to get bubbles, ripples, and all that fun stuff when you put down the new stuff. My 2 cents is to pull up that 3/4" pine and go down with some of that magical double sided plyron Bill speced. It might cost you a bit more then just covering, but in this instance I think it would probably be best. You won't have to deal with the door issues or anything like that because you won't be adding height.

See Bill, even I can be brought around. This seems to be the right application for that product.

[BillConnerASTC]

Larry - I'd always recommend pulling up what is there but hat is also the most expensive solution (almost always). To design a solution, I'd need to know how much the slab was depressed - how thick the overall floor could be built up - and if any changes - like resiliency - should be considered or added.

But replacing the strip pine with 3/4" untempered plyron is not a bad idea IF the subfloor is suitable for this. Screw down - maybe 16" on center around the perimeter and might get away with 24" on center in the field - and three coats of Rosco Tough Prime (black satin) or two now and plan on a third before long. Two often doesn't cover well but should.

Spend the time to neatly route and set floor pockets flush with floor.

Tempered and one side vs two smooth are not related. "Hardboard is produced in either a wet or dry process. The wet process leaves only one smooth side while the dry processed hardboard is smooth on both sides." and "Tempered hardboard is hardboard that has been coated with a thin film of linseed oil and then baked; this gives it more water resistance, impact resistance, hardness, rigidity and tensile strength. An earlier tempering process involved immersing the board in linseed oil or tung oil until it was 5 to 6 percent saturated, and heating to 170° C (340° F)." MDF etc. is wood particles glued together. Hardboard uses no resin - just cooks the wood fibers - more like paper - and then presses them together. Never a formaldehyde concern with hardboard or plyron.

[FatherMurphy]

A community theater near me underwent a major renovation a few years ago, and their consultant spec'ed Plyron atop plywood for the stage floor. It came pre-drilled and countersunk for mounting screws, which would be fine, except that the pattern was a grid slightly less than 8" square, the countersinking was extra deep for ensuring clearance, and the installers of course put a screw into every hole. It worked out to something like 91 screws per panel. Furthermore, they installed in February, one of the dryest months of the year, and made sure to smack every panel as tight as possible to it's neighbor before screwing.

So, when the time comes that a panel needs replacing, 91 paint-filled screws will need to be removed, and the panel pryed up from between its humidity-swelled neighbors. In the meantime, the countersink holes, even after many coats of paint, make the stage floor look like a golf ball. Furthermore, plyron isn't available in our town. The nearest dealer is 250 miles away, and wants an extra bump on the price per sheet to break up a pallet, plus the shipping, plus the higher cost of the Plyron compared to AC plywood.

The best 'new install' solution isn't always the best 'future maintenance' solution.

[Footer]

A community theater near me underwent a major renovation a few years ago, and their consultant spec'ed Plyron atop plywood for the stage floor. It came pre-drilled and countersunk for mounting screws, which would be fine, except that the pattern was a grid slightly less than 8" square, the countersinking was extra deep for ensuring clearance, and the installers of course put a screw into every hole. It worked out to something like 91 screws per panel. Furthermore, they installed in February, one of the dryest months of the year, and made sure to smack every panel as tight as possible to it's neighbor before screwing.

So, when the time comes that a panel needs replacing, 91 paint-filled screws will need to be removed, and the panel pryed up from between its humidity-swelled neighbors. In the meantime, the countersink holes, even after many coats of paint, make the stage floor look like a golf ball. Furthermore, plyron isn't available in our town. The nearest dealer is 250 miles away, and wants an extra bump on the price per sheet to break up a pallet, plus the shipping, plus the higher cost of the Plyron compared to AC plywood.

The best 'new install' solution isn't always the best 'future maintenance' solution.

That was kind of my feeling as well. For longevity I would much rather have 3/4" ply w/ 1/4" maso on top (painted both sides, etc). When I was teaching in Atlanta we went this method over the old hardwood stage it and it was fine. No bubbling even in the middle of summer. As an end user I would much rather replace a 20 dollar sheet of masonite vs a 90 dollar sheet of plywood. In Larry's case the plyron might work better just due to the 3/4" hardwood depth he already has. At that point its a direct swap without having to re-gap everything.

[BillConnerASTC]

I've never heard of pre-drilled Plyron. Sure it wasn't lami-flor which always came predrilled and which your description seems to match? It as GP product that I think is out of production. It was a high grade hardboard made with only hardwood fibres - 3 layers of 1/4" material - factory laminated and predrilled - specifically to resurface fabric mill floors to resist the steel wheeled casters. Hard as heck to run a screw into, and probably not getting it all out in one piece.

3/4 plyron is under $50/sheet - but surely not available at the big orange.

[FatherMurphy]

1/8" hardboard faces, 1/2" plywood in the middle. Was quoted $70-75/sheet by a Chicagoland dealer four years ago, after being directed to them by Plyron themselves (Olympia Products? Can't remember), not counting the pallet-breaking and freight charges. I ended up buying a couple of sheets from the flooring subcontractor to cover my part of the project (organ lift in pit). They *might* have found a similar non-Plyron product and gotten it approved as a substitution, but I'm guessing that there's some sort of patent protection on it.

[lwinters630]

Monday I will open up a section to find out what is under it.

[BillConnerASTC]

1/8" hardboard faces, 1/2" plywood in the middle. Was quoted $70-75/sheet by a Chicagoland dealer four years ago, after being directed to them by Plyron themselves (Olympia Products? Can't remember), not counting the pallet-breaking and freight charges. I ended up buying a couple of sheets from the flooring subcontractor to cover my part of the project (organ lift in pit). They *might* have found a similar non-Plyron product and gotten it approved as a substitution, but I'm guessing that there's some sort of patent protection on it.

Sounds like Plyron. Plyron is a grade or product standard that is owned by the APA APA - The Engineered Wood Association - what us to be the American Plywood Association but was rebranded as the APA-The Engineered Wood Association . Use to be available from three mills; then just Olympic Ply, and I just saw another mill is making it again. I have never seen it pre-drilled.

So other than too many holes, I'm wondering how the problems with painted filled screws poorly installed is any different than 1/4" hardboard equally poorly installed?

I've had two clients who knew what they wanted - and they wanted mdf they could get at their nearby 24 hour Home Depot and they wanted it stapled down and after a bunch of paintings and bunch of layers they'll just spend a day with a crew, a lot of wonder-bars; and a dumpster. I'd never like 2-3" of floor built up but was good for them.