Motor Coaches and Bus Conversions

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 SOUNDOWN insulation materials are useful in motor coaches for:

- lining engine and generator spaces to absorb and block noise and heat in and from those spaces,

- filling wall and floor cavities for noise reduction and privacy,

- under carpet treatments against road and engine noise,

- overhead and side linings for sound absorption in cabins,

- vibration damping of flooring to reduce radiation of road and machinery noise.

The following notes are intended to help select the proper treatements and method of application.  Because the notes are very general, they do not cover the uniqueness of individual motor coaches.  Owners and installers should feel free to contact SOUNDOWN directly for further quidance in selection of appropriate SOUNDOWN materials and methods.


The best materials for lining engine and generator spaces are the Lead SOUNDOWN composites, using either Lead/Foam or Quilted Lead/Fiberglass. These materials absorb reflecting noise within the machinery space at the same time as they create a very effective barrier against sound transmission through the walls of the spaces. They are also an effective thermal insulation.

Lead/Foam materials are the easiest to install and handle. The foam is fire retardant (U.L. 94 HF-1) and resists degradation at extended exposure of 150o F.


Quilted Lead/Fiberglass composite is even more fire resistant than the foam composite, including very low flame and smoke rating (A.S.T.M. E-84 (70) rating: Flame Spread-5, Smoke Developed-5). The quilted material is recommended in hotter engine spaces, with temperatures up to 180o F, and in situations where hot unshielded exhaust pipes are close to the insulation surface.


INSTALLATION of leaded composite should be done with mechanical fasteners in machinery spaces. Fasteners should be located 15" on center or closer. Fasteners may be SOUNDOWN insulation hanging pins attached with our high strength pin adhesive or sheet metal screws with large washers. (Do not use "self-adhesive" pins for temperatures exceeding 150o F.)


The optimum thickness of the insulation in most motor coach applications is 2", if there is enough clearance around the machinery. Thinner material should be used if clearance is a problem for the 2" materials.

Optional "Heavy Lead" SOUNDOWN composite weighing 2 lb/ft2 may be ordered for situations requiring the highest degree of sound-proofing. The standard composites are fabricated with 1 lb/ft2 lead.


Noise critical wall cavities are those built against machinery space fire walls, and those enclosing high privacy areas, such as a toilet space or a bedroom adjacent a public area.

The suggested SOUNDOWN material in these applications is Lead/Foam, in 1" to 2" thickness depending on the depth of the wall cavity. The insulation may be installed using SOUNDOWN contact adhesive, self adhesive insulation hanging pins, or it may be screwed to the wall studs.



Considerable noise is transmitted from engine and chassis vibration radiating from the floor, passing through standard carpet and padding. SOUNDOWN Carpet Underlayment blocks this noise by supporting a layer of special acoustic vinyl on an elastic layer of sound absorbing foam. The foam layer is either " or " thick. The acoustically dead cavity between the flooring and the acoustic vinyl created by the foam is critical to the sound abatement achieved.

Under thick and shag carpets, the SOUNDOWN " Carpet Underlayment is suggested for the best noise reduction. For use below firm carpeting, such as indoor/outdoor or thin industrial grades, the " underlayment may be required in order to give the proper feel under foot.



Noise inside a motor coach will reverberate, causing a build-up of noise coming from machinery, road, stereo/HiFi, or voices. Reverberant build-up is very important for spaces which are generally finished in hard materials, such as wood, glass, or plastic trim. In these situations SOUNDOWN foam-backed Headliners and Sideliners are very effective.

These materials are generally installed with SOUNDOWN contact adhesive, though they may also be stretched and stapled. Battens are frequently used to cover the edges of individual panels. A thickness of " of foam backing is an optimum compromise between acoustic performances and achieving a smooth non-pillowed appearance of the overhead. Generally, " of foam backing is all that is practical on side linings.



In new construction of coaches, lamination of the flooring with SOUNDOWN "WDI" (Vibration Damping Interlayer for Wood) is an effective way to stop road and machinery noise being transmitted through structural vibrations. A typical construction would use a " to " subfloor, with self adhesive WDI laid over and then sandwiched by a plywood finish layer " to " thick.

In motor coaches with uncarpeted floor areas, such as tiled galleys, this treatment may be used for floor coverage of those areas only.



The White or Metalized Facing is a vapor barrier, and it should face the engine. It protects the material from absorbing oil and moisture.

Cutting Material: It is best to make as few cuts as possible, so measure the sections you need and lay them out on a piece of paper. In order to minimize waste, the piece of paper or sketch on the paper should be the same as the roll size. Make your measurements as carefully as possible, because you don't want unnecessary voids. The roll of insulation can be easily cut with a razor (cutting down to the lead) and a pair of scissors to cut the remainder.

Attachment: Generally, the insulation is cemented in place. However, some back-up of mechanical fasteners are required on composite materials with lead or other mass layers.

For back-up mechanical fastening we recommend installation of screws with large washers, if the insulation is applied to wood or cored fiberglass panels. An awl may be used to make pilot holes. If a drill is to be used, operate it in reverse with foam materials, or tearing will result.If the insulation is applied to metal or uncored fiberglass - to which it may not be screwed - it may be necessary to use our bonded in place insulation hanging pins or battens for back-up fastening. A spacing of 15 inches between fasteners is acceptable.

If you use our adhesive, read the directions carefully. If you use another cement,test it for compatibility with our product. It should be applied to both surfaces, and the insulation put in place while both surfaces are tacky. If you have new wood, you may require two coats of adhesive, as the first coat may "dive in". We suggest a very light coat of adhesive on the foam surface. The foam can absorb large quantities of adhesive, and this is undesirable for two reasons: excess adhesive can loosen the laminating bonds, and excessive application can leave you with a surface that is tacky while the foam is wet underneath. Both conditions will give you a loose bond to the vessel. REMEMBER, YOU DO NOT NEED A LOT OF ADHESIVE, for all you are doing is bonding one very light layer of foam to the wood, steel or fiberglass.

Edge and seam sealing: if any edges of the material are to be exposed, it is best to use the edge sealing tape before installation. The best method is to use a tape wider than the material thickness and to apply it from the facing, over the exposed edge to the back side of the material. A small amount of adhesive applied to the area where the tape is to be applied results in better bonding to the foam or fiberglass. After installation, inside corners and exposed seams may be taped. (Quilted Fiberglass materials should have all edges taped prior to installation in order to achieve the most durable non fiber-sifting finish.)