Wood glue for wood to wood joints: PVA types and classes

What PVA wood glue is

PVA glue, short for polyvinyl acetate, is the white wood glue sold in bottles and tubs in almost every hardware shop. Loctite calls it the most common wood glue and groups both white and yellow carpenter’s glues under it. It is water-based: the glue soaks into the wood fibres and bonds as the water goes, so it cleans up with a damp cloth while wet.

Fevicol glue from Pidilite, sold as Fevicol SH for woodwork, is a typical example. Its technical data sheet describes a milky white synthetic resin emulsion with a viscosity of 200–300 poise, a pH of 4–6 and a density of 1.04–1.08 g/ml, for all kinds of wood, wood products and high-pressure laminate. Pidilite lists dowel, tongue-and-groove and mortise-and-tenon joints, solid wood edging and laminate or veneer facing on hardboard, MDF and plywood among its uses (plywood prices in Tanzania). It can be thinned with clean water, but by no more than 5%, and keeps for 24 months from manufacture.

Water resistance: D1 to D4 and Type I

The main difference between one wood adhesive and the next is how much water the joint can take. In Europe this is graded under EN 204, in four durability classes; in the United States, ANSI/HPVA Type I and Type II mark water resistance.

Water resistance: D1 to D4 and Type I

Class	Where it is meant to go
D1	interior work such as doors, furniture and panelling; wood moisture no more than 15%
D2	kitchen and bathroom furniture; wood moisture no more than 18%
D3	interiors with frequent short exposure to running or condensed water or heavy humidity; exterior work kept out of the weather
D4	interiors with frequent long exposure to running or condensed water; exterior work exposed to weather if protected by a suitable surface coating

The D1 and D2 lines come from the Ostermann guide to white glues; D3 and D4 from the German Adhesives Association (IVK) leaflet on EN 204/205. The IVK stresses that a class is set in the laboratory, on beech specimens at 12 ± 1% moisture with a 0.1 mm glue line, and cannot be checked later by testing a finished joint. A PVA adhesive sold without a class on the label gives you nothing to compare.

For wooden doors inside the house, D1 is the lowest class Ostermann names. Doors and frames that meet rain, or kitchen and bathroom joinery, sit at D2 to D4.

How to glue wood to wood

Pidilite’s directions for Fevicol SH, with the open time from Titebond’s data for Titebond III:

1. Make sure the surfaces are free of oil, grease, dust and dirt, dry, and level enough to fit snugly.
2. Stir the glue before use.
3. Spread a thin coat on both faces for hardwood, on one face for softwood.
4. Join the parts while the glue is still wet. Titebond gives 8–10 minutes of open assembly time at 21°C and 50% humidity for Titebond III.
5. Wipe off glue that squeezes out with a well-wrung wet cloth.
6. Keep the joint under pressure for 24 hours for the best result; Pidilite allows the pressure to come off after 2–3 hours and the piece to be used.

Pidilite gives coverage of about 45–50 sq ft per kg, or 4.2–4.6 m² (our conversion), and separately a spread of 150 g/m², which would give 6.7 m² per kg (our calculation: 1,000 ÷ 150). The data sheet does not explain the gap between the two figures.

Other woodworking adhesives

PVA is not the only woodworking adhesive, and the others solve specific problems. Fine Woodworking’s guide to glue calls epoxy the only gap-filling glue on the market, useful for knot holes and parts that do not fit well. It also warns that yellow PVA glue tends to creep, which makes it a poor choice for veneer with visible joints. Hide glue, made from animal collagen, is heated and bonds as it cools, as Loctite describes it, and Fine Woodworking notes that it was used in almost all furniture built before 1940. Astral Adhesives adds that polyurethane and epoxy can bond wood to metal, plastic or stone. For laminates, rubber and leather, Henkel makes a contact adhesive, Pattex glue, that bonds the moment the coated faces meet.

Where PVA is the wrong glue

A wood adhesive glue of the PVA type has limits that its makers print on the label. Titebond rules out continuous submersion, use below the waterline and structural or load-bearing joints even for its Type I Titebond III, and warns that its low pH may corrode metal, so it should be tried on a sample first where corrosion matters. Its minimum working temperature is about 7°C (45 °F) for glue, air and timber. Outside, even a D4 joint relies on a surface coating, under the IVK description.

What to check when you buy

• Class on the label. D1 to D4 under EN 204, or Type I or Type II; no class means no stated water resistance.
• Job. Interior furniture and doors need D1 or D2; wet rooms and protected outdoor joinery D3; weather-exposed work D4 with a coating.
• Pressing time. The data sheet should state how long the joint stays under pressure and when it can be used.
• Open time. For large assemblies, an open time of several minutes, such as Titebond’s 8–10.
• Shelf life. Fevicol SH keeps for 24 months from manufacture; check the date on the tub.
• Gaps. If the parts do not fit closely, an adhesive for wood to wood joints with gaps is epoxy, not PVA.