NRCA EPDM flashcards
NRCA EPDM · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- EPDM polymer type
- Ethylene propylene diene monomer, a thermoset synthetic rubber. The diene allows crosslinking (vulcanization), giving a cured, non-remeltable membrane that resists UV and ozone.
- Thermoset vs thermoplastic seams
- Thermoset EPDM cannot be heat-welded because it does not melt and re-fuse; seams rely on adhesive splicing, splice tape, or uncured EPDM cover tape. Thermoplastics like TPO or PVC are heat-welded.
- Common EPDM thicknesses
- Unreinforced EPDM is commonly 45 mil or 60 mil; reinforced EPDM is commonly 60 mil or 75 mil. Thickness is specified by the designer and confirmed in submittals.
- Splice adhesive application temperature
- Most EPDM splice adhesives require surface and ambient temperatures above roughly 40–50°F (about 4–10°C) and dry conditions. Below that, adhesion and cure are unreliable.
- Typical seam lap width
- Adhesive-spliced EPDM laps are commonly 3 in for tape systems and 4–6 in for field-applied adhesive systems. The membrane manufacturer's published lap governs the project.
- Splice cleaner purpose
- Splice cleaner removes dust, talc, oils, and release agents from the lap area before adhesive or tape is applied. Contamination is a leading cause of seam failure.
- Seam roller purpose
- A hand roller pressed along the seam immediately after mating forces out trapped air and ensures full adhesive contact. Roll from the lap center outward.
- T-joint staggering
- Where three membrane edges meet, T-joints should be staggered rather than aligned. Aligned T-joints concentrate stress and are prone to leakage, so they are covered with a splice or cover strip.
- Fully adhered attachment
- Membrane is bonded over its full area to the substrate with bonding adhesive or factory-applied adhesive. This limits billowing and is common on high-wind or complex roofs.
- Mechanically attached attachment
- Membrane is held by fasteners and plates or batten bars at a designed spacing. Fastener density increases at perimeter and corner zones to resist wind uplift.
- Ballasted EPDM system
- Membrane is loose-laid and held by river rock or pavers over a protection layer. Ballast weight must be checked against structural capacity, and the membrane needs edge restraint.
- Induction-welded attachment
- Coated metal plates are fastened to the deck, covered by membrane, and heated electromagnetically so the membrane bonds to the plate coating. No fasteners penetrate the membrane surface.
- Vapor retarder placement
- A vapor retarder is installed on the deck below insulation where the design requires it, to limit moisture migration into the roof assembly. Its need depends on climate and interior conditions.
- Cover board function
- A cover board above insulation provides a smooth, rigid substrate, spreads point loads, and improves membrane support. It can also improve fire and hail resistance depending on product.
- Positive roof slope
- Roofs should drain; a common minimum design slope is 1/4 in per foot. Positive slope reduces ponding, which stresses seams and accelerates membrane aging.
- Ponding water effect
- Sustained standing water loads the structure, stresses seams, and can promote membrane degradation and algae. EPDM tolerates incidental ponding but design should prevent it.
- UV and ozone resistance
- EPDM's saturated backbone gives excellent resistance to UV, ozone, and weathering, so it typically needs no coating. This is a key reason for its long service life.
- Petroleum product incompatibility
- EPDM swells when exposed to petroleum-based oils, grease, asphalt, and some solvents. Use compatible separators and avoid direct contact with asphalt products and solvent sealants.
- Termination bar detail
- A termination bar fastens the membrane top edge to a wall or curb, with sealant at the bar edge. It is used where membrane ends below counterflashing.
- Counterflashing function
- Counterflashing, often metal set into a reglet, covers the top of wall flashing to shed water and protect the membrane edge from weather and UV.
- Pipe boot flashing
- A pre-molded EPDM boot fits around penetrations and is clamped with a stainless or coated clamp. It provides a seamless, flexible seal at pipes.
- Drain flange sealing
- Drain and scupper flanges are set in sealant and clamped to the membrane, not merely adhered. The clamping ring compresses the membrane for a watertight connection.
- Wind uplift zones
- Corner and perimeter zones see higher uplift than the field, so fastener spacing and edge securement are tighter there. Follow the project's uplift design, not uniform spacing.
- Membrane patch overlap
- A repair patch should extend at least 3 in beyond the damaged area on all sides and use the same splicing system as the original seam, after cleaning and drying.
- Construction traffic protection
- EPDM should be protected from sharp edges, dropped tools, and incompatible chemicals. Walkway pads or pavers are used at service and high-traffic areas.
- Substrate dryness check
- Membrane should not be installed over wet insulation or a wet deck. Moisture trapped in the assembly can cause blistering and premature failure; verify dryness at hold points.
- Seam probe inspection
- A probe or peel test checks seam continuity where specified. Failed seams usually trace to contamination, moisture, low temperature, or insufficient roller pressure.
- Uncured EPDM cover tape
- Uncured (uncured gum) EPDM tape is applied over seams and cured in place, forming a homogeneous bond. It is common for T-joints and critical seams.
- Splice adhesive open time
- After applying splice adhesive, allow the specified open or assembly time before mating the lap. Rushing can trap solvent and weaken the bond.
- Roof assembly order
- Typical order is deck, vapor retarder, insulation, cover board, membrane, then ballast or coating. Each layer must be compatible with the one below.
- Edge metal securement
- Perimeter edge metal (drip edge, gravel stop, coping) must be fastened at a spacing that resists design wind loads. Loose or under-fastened edge metal is a common wind failure.
- Quality assurance hold points
- Documented checkpoints include substrate readiness, seam preparation, seam completion, flashing and termination, and final inspection. Each should be signed off before proceeding.