Outdoor cushion fabrics and foam

At a glance

From the ACT outdoor webinar deck of 29 April 2025 (a summary, not the guideline text). A voluntary US guideline that uses US test methods; it is not a UK requirement, and the figures are an example of a published threshold, not a recommendation. Check the current ACT document.

Four ways an outdoor cushion fails

An outdoor seat cushion is exposed to sun, rain, dew, cleaning chemicals and, on a hospitality terrace, spilt drinks and sun cream. Indoor test results say nothing about most of that. Four failures are worth designing against, and each has a different question for the supplier.

• Colour fades. Sunlight breaks down dyes. In the ACT work, a survey of 30 distributors found 9 who reported field failures from colour fastness to light, and the deck gives that as part of its rationale for changing the light-fastness requirement. See the next section.
• Mould and mildew. Damp cloth and a damp cushion grow mould. The ACT deck asks for a mould test (ASTM G21, zero growth) on coated cloth only; it lists no extra mould test for woven or knit cloth.
• The foam stays wet. A cushion that soaks up water takes a long time to dry, stays heavy and is the most likely place for mould. Suppliers describe quick-drying foams as open-celled, with large connected pores so that water runs through. We found no standard that tests this, so the way the foam dries is a question, not a number.
• The coating breaks down. Coated cloths (vinyl and polyurethane) can lose their surface in sunlight and damp. The deck asks for a ten-week hydrolysis test (ISO 1419) for polyurethane only.

Solution-dyed cloth, where the colour is added to the polymer before the fibre is spun, keeps its colour through the fibre and not only on the surface; the drawing shows the principle. It is a manufacturing route, not a test result, so the report is still what counts.

What the 2025 ACT outdoor guidelines say

The Association for Contract Textiles is a US trade body. The summary deck of its outdoor work group (29 April 2025) says the work began in March 2023, the proposed guideline passed a ballot in December 2024 and the ACT website was updated on 14 April 2025. The guidelines cover woven, knit and coated upholstery cloth for outdoor use, and exclude awnings, umbrellas, sunshades and sails, marine, drapery and wall coverings. New product marketed as outdoor must meet the guideline to use the ACT certification marks.

Four cautions for a UK specifier.

• US test methods. AATCC, ASTM and ISO methods are named. The UK and European route for light fastness is BS EN ISO 105-B04, which BSI Knowledge lists as current in its 2024 edition (replacing 1997). Its blue wool grades 1 to 8 are a different statement from "grade 3 at 1,000 hours" and cannot be converted: see the fabric performance tests sheet.
• Hours are not years. The 1,000 or 650 hours are laboratory exposure, and another ACT document says there is no direct correlation between test hours and hours of service.
• A summary deck. We read the work group's slides and not the guideline text. Confirm the wording before quoting a threshold.
• Voluntary. A certificate mark means a supplier agreed to the guideline. It does not make the cloth right for your terrace, and it does not cover fire.

Foam, covers and the build under them

The cloth is only half of an outdoor cushion. A good cloth over a foam that holds water, or on a base that traps it, still fails.

• Foam. Ask what the foam is, whether it is open-celled or quick-drying, how long a soaked cushion takes to dry in stated conditions, and what its compression-set and ageing results are after wet and dry cycles. These are the supplier's data: no standard for them was read. Avoid a wrapped fibre layer that holds water against the cloth, unless the supplier shows it dries.
• Cover. Make covers removable and cleanable, with a cleaning instruction per colourway. See the durable seating cleaning sheet. For zip, thread and seam, ask the workshop for details that suit weather, since seam slippage and thread life are cloth-and-sewing questions, not foam ones.
• Base. A slatted, webbed or meshed base lets water out and air in. A solid board under a sealed cushion holds a pool of water. Check the frame: see outdoor timber durability and corrosion categories for metal frames.
• Seasonal storage. Ask whether cushions are meant to be stored out of the weather. A terrace that leaves cushions out all year needs a harder specification than one that stores them nightly.
• Spare covers. Ordering extra covers with the run is easier than re-matching a faded dye lot: see the spares and attic stock sheet.

Fire: outdoor does not mean exempt

Outdoor upholstery is easily forgotten in fire planning. The British Contract Furnishing Association said in 2015 that commercial hospitality businesses should comply with the fire standards for upholstered outdoor furniture and carry out a fire safety risk assessment, and suggested the foam, fabric and all other cover materials meet BS 7176:2007 at medium hazard. That is one trade body's advice from 2015, not a rule: the level comes from the Responsible Person's risk assessment, and the legal route depends on whether the furniture is for a dwelling or a non-domestic premises. See BS 7176 hazard categories, domestic or contract fire regulations and interliners and flame-retardant upholstery.

Two cautions. First, open-cell foam burns differently from conventional foam, and a 2006 trade report said that a flame retardant suited to conventional foam did not solve the problem for a quick-dry foam: the composite must be tested as built. Second, the FIRA and British Furniture Confederation guide says flame-retardant treatments on covers must survive a water soak before testing, which matters for an outdoor cloth that will be rained on and cleaned. Ask for a report on the actual composite, with its water-soak and cleaning conditioning stated.

Outdoor cover cloth [woven solution-dyed / coated] in colourway [ ], with a test report for light fastness by [AATCC 169 / AATCC 16.3 / BS EN ISO 105-B04] stating method, grade and hours or exposure, for the colourway supplied. Where the cloth is coated, reports for mould by [ASTM G21] and, if polyurethane, hydrolysis by [ISO 1419] for [10] weeks. Supplier's cleaning instruction for the colourway to be supplied.

Cushion foam [open-cell, quick-drying], with the supplier's data on drying after soaking and on compression set after [stated wet and dry cycles]. Cushion rests on a [slatted / webbed / meshed] base that drains freely. No wrapped layer that holds water against the cover unless the supplier shows its drying data. Mock-up cushion soaked and dried before production approval.

Outdoor upholstery composite (cover, any interliner, filling) tested to [BS 7176, hazard level from the project fire risk assessment], report on the exact composite, with the water soak and cleaning cycles stated, from a [UKAS-accredited] test house. [One] set of spare covers per [10] cushions, from the same dye lot.

Standards and sources

• ACT Outdoor Fabrics: Voluntary Performance Guidelines (work group webinar deck, 29 Apr 2025): Summary slides read; the guideline document itself was not. US voluntary guideline.
• BS EN ISO 105-B04:2024: Colour fastness to artificial weathering: xenon arc fading lamp test. Current (BSI Knowledge search result); replaces the 1997 edition. The standard was not read.
• ISO 1419:2019: Rubber- or plastics-coated fabrics: accelerated-ageing tests. Fourth edition, confirmed in 2024 (ISO page, via search result); the text was not read.
• ASTM G21-15(2021)e1: Resistance of synthetic polymeric materials to fungi. Active (ASTM store listing, via search result); the text was not read.
• BS 7176:2007+A1:2011 and BS 5852: Fire tests for upholstered seating. Named only; see the library's fire sheets. Not read.

Questions we are asked

What is the best fabric for outdoor cushions?

There is no single best. Solution-dyed acrylic and coated cloths are the usual families, and what matters is the report for the colourway: light fastness, and for coated cloth mould and hydrolysis. Ask for the method, the grade and the hours, not the family name.

What does grade 3 at 1,000 hours mean?

It is a US voluntary threshold in the ACT outdoor deck for woven and knit cloth: after 1,000 hours of laboratory light exposure by AATCC 169 or AATCC 16.3, the colour change must be no worse than grade 3 on the grey scale. It is a laboratory result, not a lifespan.

Is reticulated foam mould-proof?

No source we read says so. It drains and dries quickly, according to supplier descriptions, which reduces the damp that mould needs, but the cover, the base and cleaning all matter. Ask for the supplier's data.

Do outdoor cushions need to meet fire standards?

They are not exempt. The level comes from the risk assessment for the premises, and a trade body advised in 2015 that hospitality outdoor upholstery should be tested to BS 7176 at medium hazard. Confirm with the Responsible Person and a fire adviser.

Can I use a normal indoor performance fabric outdoors?

Only with an outdoor light-fastness result for the colourway and, if it is coated, mould and hydrolysis reports. The indoor guideline thresholds for light fastness are lower than the outdoor ones in the 2025 deck, so an indoor certificate is not enough.