Overview
Procurement of factory-rated acoustic doors in Damascus is difficult and unreliable. This guide provides fabrication specifications for three STC tiers that can be built locally using available materials. Each tier is matched to specific door positions in the MediaVerse studio complex. [AC]
| Tier | STC Rating | Applicable Doors | Estimated Weight | Total Thickness |
|---|---|---|---|---|
| Budget | STC 40 | General use / non-critical | ~45 kg | ~57 mm |
| Recommended | STC 45 | D2 (Control), D3 (VO Live) | ~55 kg | 85 mm |
| Studio Grade | STC 48 | D4 (Video Studio) | ~65 kg | 85 mm |
Note: D1 (Entry) is an exterior door rated STC 50 and is procured as a complete assembly — it is NOT covered by this fabrication guide.
STC 40 — Budget Option
Tier 1 — STC 40
Solid Timber Core with MLV
The simplest acoustic door construction. Suitable where budget is the primary constraint and STC 40 is acceptable.
Leaf Construction (inside out)
| Layer | Material | Thickness |
|---|---|---|
| Outer face | Mass Loaded Vinyl (MLV), bonded | 6 mm |
| Core | Solid timber core (dense hardwood or engineered) | 45 mm |
| Inner face | Mass Loaded Vinyl (MLV), bonded | 6 mm |
- Total thickness: ~57 mm
- Estimated weight: ~45 kg
- Frame: Hardwood rebated frame, 3-point contact [AC]
- Head & jamb seals: Compression neoprene gasket (continuous run) [AC]
- Threshold: Automatic drop seal (Pemko 411 or equivalent) [AC]
Key requirement: The timber core must be dense hardwood (oak, beech, or equivalent) or high-density engineered board. Softwood cores will NOT achieve STC 40.
STC 45 — Recommended for D2, D3
Tier 2 — STC 45
Steel-Skinned Composite Leaf
The recommended construction for D2 (Control Room) and D3 (VO Live). Uses asymmetric steel skins to prevent coincidence effects. [AC]
Leaf Construction (outside in)
| Layer | Material | Thickness |
|---|---|---|
| Outer skin | Steel sheet | 1.2 mm |
| Damping layer | Butyl rubber | 1.5 mm |
| Stiffener | MDF | 15 mm |
| Core | Rockwool RWA45 | 50 mm |
| Stiffener | MDF | 15 mm |
| Damping layer | Butyl rubber | 1.5 mm |
| Inner skin | Steel sheet | 0.8 mm |
- Total thickness: 85 mm
- Estimated weight: ~55 kg
- Steel asymmetry: Outer 1.2 mm / Inner 0.8 mm — different thicknesses prevent coincidence dip at a single frequency [AC]
- Frame: 18 ga steel, welded corners, grout-filled [AC]
- Head & jamb seals: Magnetic perimeter seal + neoprene backup [AC]
- Threshold: Automatic drop seal [AC]
- Hardware: 3× ball-bearing hinges (100 kg rated), lever handle, surface closer
Asymmetric steel is critical: Using identical thickness steel on both faces creates a coincidence dip that degrades STC performance by 3–5 dB. [AC]
STC 48 — Studio Grade for D4
Tier 3 — STC 48
Enhanced Composite with Green Glue CLD
Same base construction as STC 45, with upgrades to frame gauge, damping compound, and perimeter seals. Designed for D4 (Video Studio) where Wall 7 demands STC 48 continuity. [AC]
Upgrades over STC 45
| Component | STC 45 Spec | STC 48 Upgrade |
|---|---|---|
| Frame gauge | 18 ga steel | 16 ga steel (heavier) |
| MDF damping | Butyl rubber only | Green Glue between MDF layers + butyl rubber |
| Perimeter seal | Magnetic + neoprene | Magnetic + compression double seal |
| Estimated weight | ~55 kg | ~65 kg |
Green Glue application: Apply 2 tubes (828 mL each) per m² of MDF surface. Spread evenly in random bead pattern. Assemble within 15 minutes of application. Full cure: 30 days for maximum damping. [AC]
Do NOT: Substitute silicone or construction adhesive for Green Glue — they are NOT constrained layer damping compounds and will not provide the same vibration conversion to heat. [AC]
Frame Construction
All Tiers
Rebated Frame Details
- Rebated frame: 3-sided rebate (head + both jambs) provides a positive stop for the door leaf, ensuring consistent seal compression [AC]
- Head gap: 18–20 mm between frame head and structural opening, filled with non-hardening acoustic sealant (NOT expanding foam) [AC]
- Jamb anchoring: Expansion bolts into surrounding wall framing or structural wall — NOT into acoustic partition studs [AC]
- Threshold: Level with finished floor surface; drop seal mechanism activates on door close
Do NOT: Anchor door frames into acoustic partition studs. The frame must be fixed to structural framing or masonry to avoid transmitting vibration into the decoupled partition system. [AC]
Head gap sealant: Use non-hardening acoustic sealant (Tremco or equivalent). Expanding polyurethane foam is NOT acceptable — it hardens and creates rigid bridges that transmit sound. [AC]
Seal Types Explained
Reference
Three Seal Mechanisms
| Seal Type | Location | Mechanism | Used On |
|---|---|---|---|
| Compression gasket | Head + both jambs | Neoprene D-profile, continuous run. Compresses when door closes against rebate. | All tiers |
| Drop seal | Threshold (door bottom) | Spring-loaded plunger retracts when door opens; drops to meet threshold plate on close. | All tiers |
| Magnetic seal | Head + both jambs | Embedded magnetic strip + steel keeper strip. Provides pull-to-close force ensuring positive contact. | STC 45 + STC 48 |
Compression gasket life: Neoprene D-profile gaskets have a service life of 3–5 years before compression set reduces their effectiveness. Plan for replacement during annual maintenance inspections. [HP]
Drop seal adjustment: The drop seal mechanism must be adjusted so the seal contacts the threshold plate across its full width. A 1 mm gap at any point can degrade door STC by 5–10 dB. [AC]
QC & Testing
Verification
Fabrication QC Checklist
- Leaf thickness matches specification for tier (±2 mm)
- Steel skins are asymmetric (STC 45 / STC 48 tiers) [AC]
- Green Glue applied at correct coverage (STC 48 tier only) [AC]
- Frame rebate depth accommodates full leaf thickness + seal compression
- All welds on steel frames are ground smooth and sealed
- Grout fill is complete in steel frames (no voids)
Installation QC Checklist
- Frame anchored to structural framing (NOT partition studs) [AC]
- Head gap sealed with non-hardening sealant [AC]
- Compression gaskets compress fully on all three edges when door is closed [HP]
- Drop seal contacts threshold across full width [HP]
- No daylight visible around any door edge when closed [HP]
- Magnetic seal (if applicable) provides audible click on close
- Door closer speed: 3–5 seconds from 90° to latch
- Hinges support door weight without sagging
Pass criteria: Zero visible daylight around all edges, full seal compression on head and both jambs, drop seal flush contact with threshold, and door weight supported without hinge sag.
Do NOT: Accept any door installation where daylight is visible around any edge. Even a 1 mm gap can reduce effective STC by 5–10 dB, negating the entire fabrication effort. [AC]