Foaming in a door frame with 2K door frame foam
Contents
What you need
Project template “Door frame and installation with PU foam”The frame is set plumb and level, wedged and braced, then foamed behind from the dual cartridge with 2K door frame foam: timber frames up to 40 kg door leaf weight at at least six spots of about 20 cm length each, steel frames and all frames over 40 kg over the full area. The joint gap may be 20 mm at most. At +20 °C the foam can be cut after about 5 minutes and the braces can be removed after about 20 minutes – only then are wedges and braces released, the excess cut off and the connection joint closed.
Shopping list
Basic set (always required)
2K door frame foam 210 mlPropellant-free 2K PU foam, cuttable after approx. 5 minutes, no shrinkage and no post-expansion. According to the manufacturer, one cartridge is enough for 1 to 2 door frames.
To the product
2K dual cartridge gunAll-metal manual gun for dual cartridges up to 220 ml (2 x 105 ml). The 17:1 transmission ratio presses out both chambers synchronously – only that way is the mixing ratio right.
To the product
Fine crepe tape 50 mFor masking the frame rebate and wall edge. Fine crepe, removable without residue, resistant to water, thinners and oil.
To the productOptional – depending on the installation situation
- 2K fast-setting door frame foam set incl. gun, 16 x 210 ml – when several doors are due: gun and 16 dual cartridges in one package.
- Ottopur Turbo door frame foam 2 x 105 ml – alternative from the OTTO system, propellant-free, cuttable after approx. 5 minutes at 20 °C, brace-removable after approx. 15 to 18 minutes.
- Otto caulking gun H248 – the manual gun intended by the manufacturer for the Ottopur Turbo, for 2 x 105 ml.
- Click&Clean gun and foam cleaner 500 ml – for fresh foam and for cleaning the inside of the gun.
- Ottopur Cleaner gun cleaner 500 ml – the matching cleaner if you work with the Ottopur system.
- PE dust sheet – mandatory with a finished floor covering, because cured foam can only be removed mechanically.
- Painter's acrylic A220 Turbo 310 ml – for the connection joint between frame and wall, immediately paintable up to 5 mm joint width.
- Primer for strongly absorbent or porous substrates (e.g. plasterboard and aerated concrete walls) – as specified by the respective foam manufacturer.
Tools
- Wedges and frame braces
- Spirit level (at least 1 m) and folding rule
- Utility knife for the cartridge tip and the foam excess
- Cardboard or paper for the purge and for laying down the gun
- Disposable gloves, cardboard strips for the wall gap if required
How many cans or cartridges you need for your project is worked out by the expanding foam calculator. You will find all foams of this type in the category 2K foam & door frame foam.
Why 2K door frame foam and not simply gun foam?
A door frame is a sensitive component: it stands plumb to the millimetre, and any pressure from outside distorts it. This is exactly what 2K foam is designed for. It cures through a chemical reaction of both components – not via humidity – and does so free of pressure and stress, without shrinkage and without post-expansion. Moistening the substrate is not necessary. The result: the frame stays where you aligned it, and you can release the braces after only about 20 minutes instead of hours.
The second difference is the pace – and that is the real challenge. The reaction starts around 12 to 15 seconds after dispensing, and after about a minute the foam is tack-free. A work pause of more than 10 seconds is enough for the foam to cure in the static mixer and make the mixing tube unusable. So you work quickly and in one pass – which is why it pays to set everything up beforehand. If you want to read up on the difference from 1K foams in detail: Gun foam or hand-held foam and Applying PU foam properly.
Six foam spots, three per post, each around 20 cm long – this is how timber frames up to 40 kg door leaf weight are fixed. Steel frames and heavier door leaves are foamed over the full area.
Step by step
Check the substrate and measure the gap
The substrates must be clean, dry, and free of dust and grease. Strongly absorbent and porous substrates – such as plasterboard or aerated concrete walls – are treated with primer beforehand, otherwise the wall draws off the liquid components before the foam rises. Measure the joint gap between frame and masonry: it may be 20 mm at most.
Check: Measure the gap at at least three places per post – everywhere 20 mm or less. Wipe your hand over the reveal: if dust stays on your finger, vacuum once more.
Set the frame, wedge it and brace it
Set up the frame, align it with wedges and fix it with braces – the braces sensibly sit at the height of the later foam spots, because that is where the pressure is absorbed. Only when both posts are plumb, the diagonals are equally long and the door leaf has even clearance all round is foaming done. Readjusting is no longer possible later.
Check: Spirit level on both posts and on the head piece; compare diagonals with the folding rule (difference preferably under 2 mm). Hang the door leaf as a trial and check the air gap, then remove it again.
Mask, cover, block off the gap
Mask the frame rebate and wall edge with fine crepe tape, protect the floor with film. Cured foam can only be removed mechanically – masking is therefore not busywork but damage prevention. With the Ottopur Turbo the manufacturer includes cardboard strips: they are placed in the wall gap in the area of the foam spots so that the still-liquid components do not run downwards before they foam up.
Check: Press the tape down firmly at the edge with your thumb – no open spots under which foam can creep.
Prepare the cartridge and purge
Cut off the cartridge tip with the knife, fit the static mixer, insert the dual cartridge into the 2K gun. Then run it out steadily and without jerking onto cardboard until both components emerge homogeneously mixed. The application temperature is +10 °C to +30 °C – in a cold shell this is the most common reason for trouble.
Check: Correctly mixed foam is light yellow and even. As long as it emerges streaky or darker, keep pressing onto the cardboard – not into the joint.
Place six foam spots – quickly and in one pass
Introduce foam through the mixer into the wall gap: for timber frames for door leaves up to 40 kg at least six spots of about 20 cm length each, that is three per post. Steel frames and all frames with a door leaf weight over 40 kg are foamed over the full area. Work without interruption: pauses over 10 seconds cure the foam in the mixing tube. Immediately after application, lay the cartridge together with the gun on cardboard or paper while foam residues are still expanding. If you do have to interrupt, take off the mixing tube and fit a new one later.
Check: All six spots placed, no pause over 10 seconds, foam emerges uncontrolled from the rebate nowhere. A 210 ml cartridge is enough for 1 to 2 frames – if it runs empty beforehand, the dosage was too high.
Leave to cure – and touch nothing
Now patience pays off, in minutes rather than hours: tack-free after about a minute, cuttable after about 5 minutes, brace-removable after about 20 minutes at +20 °C and 65 % relative humidity. The Ottopur Turbo is brace-removable after about 15 to 18 minutes. Lower temperatures lengthen curing considerably – so allow more time in an unheated new build.
Check: Fingernail test at a foam spot – if the foam can no longer be pressed in, installation strength has been reached. Only then release braces and wedges.
Cut off the excess and close the connection joint
Cut off protruding foam flush with a knife only after installation strength has been reached, pull off the tape, hang the door leaf and check that it moves freely. The joint between frame and wall is closed with paintable painter's acrylic: immediately paintable up to 5 mm joint width, after around 4 hours for 5 to 10 mm. Application temperature +5 °C to +35 °C, skin-over time around 10 minutes at 23 °C – do not rework after that. Remove fresh foam or acrylic residues immediately; cured material comes off only mechanically.
Check: The door stays in any position, does not scrape and closes without pushing. The acrylic joint is filled without bubbles and pulled smooth.
Curing times and checks
| Phase | 2K door frame foam at +20 °C | How you check it |
|---|---|---|
| Reaction start | approx. 12–15 seconds | Foam visibly begins to rise |
| Tack-free | approx. 1 minute | Touch with a glove – nothing sticks |
| Cuttable | approx. 5 minutes | Knife test on the excess – cuts without smearing |
| Brace-removable (installation strength) | approx. 20 minutes (Ottopur Turbo: approx. 15–18 minutes) | Fingernail test at the foam spot – no more indentation |
| Connection joint paintable | up to 5 mm immediately, 5–10 mm after approx. 4 hours | Acrylic is dry and matt on the surface |
All values apply at +20 °C and 65 % relative humidity. Application temperature of the foam: +10 °C to +30 °C. Lower temperatures lengthen curing.
Common mistakes – and how to avoid them
- Work pause over 10 seconds. The foam cures in the static mixer, the mixing tube is ruined. Lay everything out beforehand; for an unavoidable interruption, take off the mixing tube and fit a new one later.
- Only three or four foam spots. Timber frames up to 40 kg door leaf weight need at least six spots of about 20 cm each, steel frames and heavier leaves full-area foaming.
- Joint gap over 20 mm. Beyond that the gap is no longer intended for these foams. Pack out or brick up the gap beforehand, do not simply introduce more foam.
- Purge straight into the joint. The first centimetres are not mixed homogeneously and cure uncontrollably. Run it out onto cardboard first until the foam emerges light yellow.
- Braces released too early. Before installation strength is reached, the frame pulls. Wait for the fingernail test, then release.
- Unprimed plasterboard or aerated concrete walls. Strongly absorbent, porous substrates take the basis away from the liquid components – prime beforehand.
- Tackling cured foam with cleaner. Cleaner works only on fresh foam. Remove stains immediately, therefore; for further reading: Removing PU foam and PU foam will not cure.
Frequently asked questions
How many door frames does one cartridge cover?
According to the manufacturer, a 210 ml dual cartridge is enough for 1 to 2 door frames; the foam yield is about 5 to 5.5 litres per cartridge. When foaming steel frames over the full area, allow correspondingly more.
How long must the door frame foam cure before I release the braces?
At +20 °C and 65 % relative humidity the foam is cuttable after about 5 minutes and brace-removable after about 20 minutes. The Ottopur Turbo is brace-removable after about 15 to 18 minutes. Lower temperatures lengthen curing.
Do I need a special gun?
Yes. 2K foam comes in dual cartridges and must be pressed out of both chambers simultaneously and in the right ratio. For that there are 2K dual cartridge guns – for example the all-metal gun for cartridges up to 220 ml with a 17:1 ratio or the caulking gun H248 for 2 x 105 ml. An ordinary cartridge gun cannot do this.
Do I have to moisten the substrate?
No – 2K foam cures through the reaction of both components, moistening the substrate is not necessary. The substrate must, however, be clean, dry, and free of dust and grease; strongly absorbent and porous substrates such as plasterboard or aerated concrete walls are treated with primer beforehand.
How many foam spots are needed?
Timber frames for door leaf weights up to 40 kg are fixed at at least six spots of about 20 cm length each. Steel frames and all frames with a door leaf weight over 40 kg are foamed over the full area. The joint gap should be 20 mm at most.
Which building material class does door frame foam have?
The 2K door frame foams described here correspond to building material class B2 to DIN 4102-1. Where there is a fire protection requirement – for example with fire doors – a system tested for that must be used, not a standard door frame foam.
Further reading
- Instructions: applying PU foam properly
- Instructions: RAL window installation – procedure and materials
- Guide: Gun foam or hand-held foam
- Expanding foam calculator: how many cans of PU foam?
- All guides and instructions at a glance
Questions about choosing materials? Baustoffheld, Lindenstrasse 56, 47623 Kevelaer, phone +49 (0) 2831 - 916 77 03.
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