Strip Brush Seal vs Rubber Seal: Which Gap Seal to Use
Comparison · 6 min read · updated 2026-10-24
Gaps around doors, machine guards, conveyors and cable entries are closed with one of two families of seal: a strip brush (filament held in a metal or plastic channel) or a rubber profile (a blade, bulb or fin, often EPDM). Both are cheap compared with the cost of the drafts, dust or pests they keep out, so the choice should be made on performance, not price.
The short version: rubber seals better when the gap is consistent and the seal is mostly static; brush handles irregular gaps, motion and abrasion better. The details below show where the line falls.
Comparison table
| Factor | Strip brush seal | Rubber seal (EPDM bulb, blade, fin) |
|---|---|---|
| Air and water tightness | Lower — less weathertight | Higher; bulb seals insulate best |
| Irregular or pitted surfaces | Very good — bristles fill pits | Bulb and fin good; flat blade poor |
| Friction on moving parts | Low | Higher; blade can drag or tear |
| Tolerance to sliding and abrasion | Good | Can tear on rough edges |
| Light, dust, insects | Good | Good |
| Typical temperature range | Set by filament (e.g. PA66 nylon melts ≈257 °C) | EPDM ≈ −50 to 150 °C, grade dependent |
| Typical uses | Sliding and roller doors, conveyors, machine guards, cable entries | Hinged doors, enclosures, windows, static joints |
Where a strip brush wins
Example: our garage door seal strip brush uses 0.3 mm PA66 nylon with a 100 mm trim in an F-profile aluminium carrier, listed for −40 °C to above 100 °C.
- Uneven floors and frames: bristles bend over high spots and fill pits in rough concrete, where a rigid blade gaps on one side and drags on the other.
- Movement: sliding doors, roller shutters, escalator skirts, conveyor sides and machine guards. Brush adds very little friction and does not tear when something passes through.
- Cable entries and slots: cables pass through bristles and the seal closes around them.
- Large or variable gaps: long-trim brush bridges gaps that would need a very large rubber profile.
Where a rubber seal wins
- Weather and air tightness: rubber bulb seals compress into a continuous barrier and insulate better than brush, which industrial suppliers rate as less weathertight.
- Water: a bulb or blade can stop water running under a door; a brush only slows it.
- Static joints such as enclosure doors and panels that close against a flat frame.
- Outdoor exposure: EPDM resists heat, ozone and weathering well and is the standard rubber for vehicle and building weatherstrips.
Life, maintenance and cost
Brush seals wear at the tips and can take a permanent splay if fitted with too much interference. Pick the shortest trim that just touches the surface; extra length only drags. Rubber seals fail by compression set, hardening or tearing, particularly where something slides across them.
Metal-channel brush strips are easy to replace in their aluminium holders, and the filament can be matched to the job: nylon for general use, PP for wet areas, anti-static or flame-retardant grades on request. See our metal-channel strip brush guide for channel sizing.
Filament choice inside a brush seal
A brush seal's limits are set by its filament, so specify it rather than accepting a default:
- Nylon (PA66): the general-purpose choice; tough, good bend recovery and a melting point around 495 °F (257 °C).
- Polypropylene: absorbs almost no water (<0.1%), so it suits wet areas, but it melts at about 320 °F (160 °C) and takes a set more easily.
- Horsehair: a soft natural seal for doors and enclosures where a gentle contact is wanted.
- Anti-static carbon fibre: for electronics, film and paper lines that need static discharge.
- Metal channel material: galvanized steel for general use, stainless steel or aluminium where corrosion matters.
Hybrids: brush plus rubber
Many door bottoms combine both: a brush that rides over the threshold with a rubber insert behind it for a tighter seal. The reverse also exists — our clip-on TPV/TPE seal brush tufts bristles into a flexible thermoplastic rubber clip profile that presses onto sheet-metal edges without screws, with a listed working range of −60 °C to 135 °C.
A hybrid is worth considering when you need brush's tolerance of uneven surfaces but rubber's better draft resistance.
Decision checklist
- Does the part move across the seal? Yes → brush.
- Is the surface uneven or rough? Yes → brush, or a bulb/fin rubber seal; avoid flat blades.
- Must the seal stop water or drafts tightly? Yes → rubber, or a brush/rubber hybrid.
- Gap size range: measure the largest and smallest gap along the length.
- Mounting: carrier profile (H, F, T or clip), length and fixing.
- Environment: temperature, oils, UV, chemicals. Send details via Request a Quote or browse strip brushes and brush seals.
Frequently asked questions
- Is a brush seal better than a rubber seal on a door?
- It depends on the door. Brush seals suit uneven floors, sliding and roller doors, and frequent movement. Rubber bulb seals insulate and keep out water better on doors that close against a flat threshold.
- Do brush seals keep out water?
- Only partly. Brush slows wind-driven rain and splashes but is not watertight. Use a rubber seal or a brush seal with a rubber insert where water must be stopped.
- What temperature can EPDM door seals take?
- Reference data gives EPDM a service range of roughly −50 °C to 150 °C, but the actual limit depends on the compound, so check the datasheet for the specific seal.
- How long should the bristles on a brush seal be?
- Choose the shortest trim that bridges the largest gap with light contact. Too much interference bends the bristles permanently and increases wear.
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Need help choosing or a custom spec?
Send us your machine, drawing or requirement — we'll match the right brush and quote, usually within one business day.