This comparison comes up on almost every flat roof replacement, extension or garage roof job, and it is worth saying plainly: the covering is rarely the reason flat roofs fail. Poor falls, inadequate insulation ventilation and bad upstand detailing cause far more leaks than the choice between these two materials.
How they are installed
EPDM is a synthetic rubber sheet, supplied in widths that cover most domestic roofs in one continuous piece with no joints at all, bonded to the deck with adhesive. Fewer joints mean fewer places for water to find a way in.
Felt is applied in multiple layers, traditionally torched with a flame to bond the layers and seal the laps, though cold-applied and self-adhesive felt systems are also common now. Joints between rolls are the weak points and rely on correct overlap and heat-sealing.
Movement, damage and repair
EPDM is highly tolerant of the roof deck moving slightly with temperature and building settlement, because the rubber sheet flexes rather than cracking. Felt is more rigid once bonded and can crack at stress points if the deck moves.
Both are repairable, but felt patch repairs are a familiar job for almost any roofer and can be done without specialist EPDM adhesives or seam tape, which is part of why felt remains common on garages and outbuildings.
Fire risk during installation
Torch-on felt involves an open flame during installation, which carries an obvious fire risk, particularly close to timber eaves, existing roofs or in occupied buildings. Cold-applied felt and EPDM avoid this entirely, which is one reason EPDM has become the more common specification on extensions built close to an existing house.
Access and how the roof is worked on
EPDM sheets are typically brought to the roof in a single large piece and need enough clear access to manoeuvre and lay them without folding or creasing the membrane, which can be awkward on a tight garage roof or a rear extension with limited side access.
Felt is applied in smaller rolls, which makes it more practical on roofs with restricted access or where materials have to be carried through the house rather than craned or hoisted into place.
What a written quote should specify
For EPDM, the quote should state the adhesive system used, how upstands and outlets are detailed, and the warranty offered by the membrane manufacturer, since workmanship and product warranties are often separate.
For felt, the quote should specify the number of layers, whether it is torch-applied, cold-applied or self-adhesive, and what fire precautions are in place if torching is used close to timber or an occupied building.
Common questions
Which lasts longer?+
Both, properly installed on a correctly detailed deck with adequate falls, give a long service life. Failures in either material are far more often traced back to poor falls or deck movement than to the membrane itself wearing out.
Is EPDM more expensive than felt?+
Material cost is generally higher for EPDM, but the seamless installation can offset some of that in labour, and the reduced repair frequency over time is worth weighing against the higher upfront material cost.
Can felt be laid without a naked flame?+
Yes, cold-applied and self-adhesive felt systems exist and remove the fire risk of torching, though traditional torch-on felt is still widely used where access and site conditions allow it safely.
Get a flat roof quote
We'll inspect the deck and falls before we ever discuss covering material, then give you a written quote for whichever system is right for that roof.