# Homasote as an element of stage platforms?



## jneveaux (Jun 6, 2019)

Ran across this description recently on the Wikipedia entry for Homasote (https://en.wikipedia.org/wiki/Homasote):

_Homasote is also widely used in theatrical sets as a noise deadening layer for stage platforms; which consist of a 3⁄4-inch (19 mm) plywood sublayer, a 1⁄2-inch (13 mm) Homasote layer, and a 1⁄4-inch (6.4 mm) Masonite top layer.
_
There is no source for the statement listed. Is anyone doing this combination on a regular basis? I don't recall seeing it in any scenery textbooks.

I know the historical use of homasote included many vertical wall applications (_ala_ sheetrock) and as sound deadening for permanent floor/ceiling/roof installations, but I haven't seen it used onstage.


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## RonHebbard (Jun 6, 2019)

jneveaux said:


> Ran across this description recently on the Wikipedia entry for Homasote (https://en.wikipedia.org/wiki/Homasote):
> 
> _Homasote is also widely used in theatrical sets as a noise deadening layer for stage platforms; which consist of a 3⁄4-inch (19 mm) plywood sublayer, a 1⁄2-inch (13 mm) Homasote layer, and a 1⁄4-inch (6.4 mm) Masonite top layer.
> _
> ...


 *@jneveaux* Our local arena used to lay 4' x 8' sheets of Homasote on thin polyethylene (to keep the Homasote dry) on the ice surface prior to laying the basketball floor or a floor for concert seating on top. I understood they were doing this to thermally insulate the floors from the ice and likewise isolate the ice from the heat of the audience and / or concert lighting which in turn let them run the brine chillers a little slower reducing noise and conserving electricity. The Homasote sheets suffered a lot of handling damage and required carts and space for storage during times when the ice was in use.
At the time, our city owned both the arena and our largest soft-seater. Once or twice Homasote from the arena was laid on our main stage topped by Masonite prior to laying a dance floor; in this application it was purportedly to further cushion our already sprung deck. 
*EDIT:* From memory (This was back in the 1980's) our city's Homasote was 5/8 or 3/4 inch thick. 
Toodleoo!
Ron Hebbard


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## jneveaux (Jun 6, 2019)

RonHebbard said:


> *@jneveaux* Our local arena used to lay 4' x 8' sheets of Homasote on thin polyethylene (to keep the Homasote dry) on the ice surface prior to laying the basketball floor or a floor for concert seating on top. I understood they were doing this to thermally insulate the floors from the ice and likewise isolate the ice from the heat of the audience and / or concert lighting which in turn let them run the brine chillers a little slower reducing noise and conserving electricity. The Homasote sheets suffered a lot of handling damage and required carts and space for storage during times when the ice was in use.
> At the time, our city owned both the arena and our largest soft-seater. Once or twice Homasote from the arena was laid on our main stage topped by Masonite prior to laying a dance floor; in this application it was purportedly to further cushion our already sprung deck.
> *EDIT:* From memory (This was back in the 1980's) our city's Homasote was 5/8 or 3/4 inch thick.
> Toodleoo!
> Ron Hebbard



Ron, I've seen that use in ice arenas, and noticed how the homasote sheets got banged up. I'm still wondering about the use in stock stage platforms though. Thanks for the reply.


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## sk8rsdad (Jun 6, 2019)

It can be used as the filling part of the sandwich in triscuit style decking.


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## MNicolai (Jun 6, 2019)

Might also see it referred to as Celotex. Yes, it's a somewhat common way of dampening sound on platforms.

I want to say that in college, our stock platforms were just 3/4" ply. We added the Celotex and Maso layers as-needed. Could be mistaken on that.


EDIT:

From the STOCK SCENERY & CONSTRUCTION HANDBOOK.





Also, I happened to have a sample on-hand that goes under yet a different name:


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## DRU (Jun 6, 2019)

I've used homasote that way before. A summer stock I worked for had a touring show with a raked platform built with 2x4 framing, a layer of homasote, then a layer of 3/4 ply.

Another summer stock I worked for had the homasote between the 2x4 framing, not as an extra layer of lid. It was rough fitted between the framing and the gaps were filled by Great Stuff expanding foam. 

I wouldn't consider it a requirement for platforms, but more of an upgrade to solve a problem of footstep echo under a platform.


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## Van (Jun 6, 2019)

I would never put a layer of homasote directly under the topping. When I have used it for platforms it has always been framing, homasote, 3/4 ply, MDF. Homasote doesn't have enough compression strength to hold up to a point load when used directly under something like MDF, Maso, or luan.


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## BillConnerFASTC (Jun 6, 2019)

I'm guessing you are talking about Homasote's 440 Soundboard. They have lot of products all called Homasote something or other - including decking products for floorsand roofs. I have seen some theatre platforms with ply, 440, and just canvas. It's often used under carpet. Good thermal and sound insulation.


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## gafftapegreenia (Jun 6, 2019)

Van said:


> I would never put a layer of homasote directly under the topping. When I have used it for platforms it has always been framing, homasote, 3/4 ply, MDF. Homasote doesn't have enough compression strength to hold up to a point load when used directly under something like MDF, Maso, or luan.



Yup, learned that one the hard way. In college we did a Homasote floor for Sunday in the Park. Then, when the rental grand piano was delivered, it was rolled directly across the floor, leaving nice deep tracks in its wake.


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## JonCarter (Jun 7, 2019)

We used to cover our platform tops with old fashioned horsehair carpet padding--about 1/4"-3/8" thick, then a finish surface of muslin stretched & stapled. Deadened footsteps beautifully. It would barely compress at all. Doubt if the new foam stuff would work, tho, but might be worth a try.


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## lipinski (Jun 7, 2019)

This was a HOT debate when i first got into Webster Conservatory in undergrad. Webster had been doing a layer of homosote cross sheeted on top of the stock 3/4" ply deck frames, followed by another cross sheet of maso. The purpose was sound dampening. It was sort of an air quality night mare. (don't take a router to that stuff unless you have a force airsupply mask). 

Eventually the sound department did some measuring and tested homosote dampened deck against a control of just maso, as well as third variable that had carpet under the deck's ply in between the framing. They put mics at the toe, a listening distance away, and took a tap mic on the deck for comparison. I can say definitively, homosote sublayer does a dampen of actual footfall (shoes hitting deck) and almost nothing for the "drum" effect" you can get with platforms sitting on concrete. (this was mostly for applications in our basement black box). The carpet did more than anything else for dampening that drum effect. The simplest solution to dampen the drum (which we think is the skin of the platform vibrating and creating positive and negative pressure within the negative space beneath the platform) was actually to shim the platforms in homosote. It was remarkably effective. By junior year, we banned sub skins in homosote (mostly for air quality purpose actually) and went to using a 3"x 4" shim under each platform leg. That with a few pieces of upholstery foam left in the negative space made for shockingly quite deck. All of this testing happened in 2012ish. Team sound spent an absurd amount of time trying to isolate the sources of vibrations generated by platforms. I don't know how truly scientific it was. But after much debate, the homosote sublayer was ruled a waste of time, money, and air quality.

We also found that the homosote sublayer made the sound of footfall almost weirdly quite, while the reverberating drum sound was only marginally damped. It makes for an echoy delayed footstep sound. Dampening the underside made more for a tight sounding footfall that our sound team could expertly balance with their outputs. 

Jon Carter, the next time i need eerily quite deck, I'm trying you carpet padding idea. Do you wrap the deck in muslin in it's stock pieces? or do you ground cloth each layout assembled?

I know a lot of this was extraneous. In short, I'm positing that the homosote sublayer is an old practice that doesn't yeild great results.


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## BillConnerFASTC (Jun 7, 2019)

The MSDS makes it seem pretty harmless and inert.


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## RonHebbard (Jun 7, 2019)

BillConnerFASTC said:


> *The MSDS makes it seem pretty harmless and inert. *


 *@BillConnerFASTC* and * @lipinski* Hardwood reads as pretty innocent and harmless *until* you're a young kid sanding furniture 8 hours a day / 40 hours a week in a 1920's British furniture factory having to decide which of your eyes you want to sacrifice in order to have the cancerous growth in your sinuses exorcised some six decades later. 
Toodleoo! 
Ron Hebbard


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## josh88 (Jun 7, 2019)

I've definitely had decks in more than one venue made with layers of homesote in them. I've also done a lot of scenery/floors with it on top because with a coating of VSSSD it makes great flagstones or pavers. Route designs into it, harden it, and it looks great.


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## JonCarter (Jun 8, 2019)

@lipinski It depended on the set. For one-set shows we built all the platform pieces, assembled on stage, then padded, covered & painted. For sets requiring changes we built, padded & painted each platform separately, then assembled the design configuration on stage. The problem with this is that the joints between platforms and the edges of their pads are rather noticeable.


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## lipinski (Jun 8, 2019)

BillConnerFASTC said:


> The MSDS makes it seem pretty harmless and inert.


Hi Bill!

I hadn't looked at those sheets in a while. You're point is well taken, I was being a little alarmist. But I stand by the main idea of my warning. Compare the vocab to fiberglass's msds. While thiers no exposure warning, the vocabulary (and physical expierence of having it on your skin) is very similar. 

My point is: mind your ppe with this stuff. Be precautious. My forced air supply comment was probably alarmist, but the context was routing a half inch board in a (poorly ventalated) basement. Forced air was appropriate there. Cutting shims in a shop: we were fine with a vacuum on your saw, long sleeves, and a dust masks. I do recommend avoiding routing it in general. 

It's definitely true that the msds indicates it's a workable non-hazardous material. It is an irritant, not a toxic material. Just mind your ppe. It feels a lot like fiberglass on your skin and lungs. It doesn't have the same ability to cut into you and stick, but it does form large light-weight airborne particles. I think people should be aware of air quality when considering this material. 

Hope thats fair and clearer.


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## BillConnerFASTC (Jun 8, 2019)

Very fair. Seems no worse than most (untreated) wood products, all of which should require similar precautions.


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## JChenault (Jun 8, 2019)

When I was learning how to build scenery, I interned for a year at the Asolo theatre in Sarasota. We put homasote on top of just about every platform we built. It was quiet and helps up pretty well. 

This was before the days of MSDS (1973) but it did not irritate skin or lungs.


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## Colin (Jun 8, 2019)

I've often topped stock platforms with 440 with and without hardboard on top. It isn't always the right thing, just another trick in the bag.

It does help deaden foot strikes on top but not so much the drumming resonance underneath. I've considered the possibility but not yet had the need to try for better/different performance by skinning the bottom of a platform with it instead or in addition to the top.

Like Josh says, it can be a useful top layer and takes a variety of treatments well, which can also improve durability. Sure, don't roll your grand piano or fully loaded pallet jack over it even with a hardboard layer on top, but that kind of traffic is pretty rarely coupled with a need to deaden footsteps in my experience. I can't think of a time I've needed to build for such a point load and thought "gosh I wish I could do Homasote here". Two coats of paint tends to be plenty of durability for short duration, light traffic, other than at exposed edges where footsteps can chew it up and cause some slipping and tripping concerns. At step edges I've sometimes just gaffed or dutchmaned the edge and other times done a wood nosing.

I keep enough sheets in stock to match platform stock plus a little. It lasts a long time because we keep most sheets whole or cut into 4x4s and 2x8s to match stock plats. Plus, when you're skinning it with something else it doesn't have to be pretty - you can piece it together with whatever weirdo scraps you've got.

The other really nice thing about using it over the top of a platform system is that it does a great job of easing any inconsistencies in the platform surfaces. Got some gnarly old stock lids with paint globs and random old fasteners hopelessly stuck on not remotely flush? A little twist in a frame? Or one frame freshly built from wood that sat outdoors in the rain for a week before it got delivered, trying to rest next to another frame that's four or fourteen years old, bone dry and 1/8" thinner? A perpendicular layer of 440 is soft enough to, sometimes with a little convincing, compress around all those obstacles considerably better than just a 1/4" skin of something denser. Got to be careful with screw depth adding hardboard on top though because of the softness - it can leave you with noticable puckers where screws compressed the Homasote too much.

Yes, the dust is an awful nuisance and a respiratory concern just because it is so fine and plentiful. The MSDS is not intimidating, but any dust that fine and light is a bad thing. I've never encountered anyone having any skin reaction though. Really good dust extraction (Festool...) helps but some is getting in the air no matter what. _Unless_ you cut and shape it with utility knives and other very sharp hand powered blades, which takes about the same time when you factor in near zero cleanup versus the seemingly eternal ash cloud you get from power tools. It's not too bad, especially if the appearance of the cuts isn't critical. I like to score both sides - one to two passes each - and snap it off, then clean the snapped edge with a sharp blade if needed. Sometimes I don't even bother scoring both sides - like cutting drywall.


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## Dan Fischer (Jun 12, 2019)

We have been building 4x8 and other sized platforms for years in our theatre and our full inventory has a layer of 440 soundboard sandwiched between the frame and the 3/4” plywood. We found that putting the homasote on the top wore down too quickly plus it almost makes is too quiet. Under the plywood you still get natural room acoustics and the homasote never wears down that way. Not the greatest picture ever but it’s what I’ve had in my phone. You can see the sandwiched layer of 440.


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## Apmccandless (Jun 12, 2019)

I worked on Webster Campus (not for the school for the Rep) from 2007-2010. I almost never see homosote around here (St. Louis) everyone was/is using 1/2" Asphalt Sheeting it works well to deaden footfall and is very cost effective. I think that may be where the PPE concern may be coming from. I think another issue that may have contributed to the problems lipinski noted was that i saw students use a flush trim bit to cut the sheets to size rather than using a saw to rough cut the sheet and finish with the router. Now that I work in business meetings and tradeshows we use engineered decks with rubber feet on the legs and carpet on the deck. No homosote (or Asphalt Sheeting) in sight.

https://www.google.com/shopping/pro...bo1D_a-AFtMg8ta1fWoaAnbuEALw_wcB,gclsrc:aw.ds


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## BillConnerFASTC (Jun 12, 2019)

Much different than homasote. http://msds.gp.com/msdsinternet/Open.aspx?_do=di0FVqXMixY1r9gCy0ThpQ==

Bad juju.


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