Osmo Exterior Gap Sealer 310ml

  5.0/5.0   4 reviews
  • A professional grade, single component, acrylic silicone sealant for exterior use
  • Perfect for sealing window and door frames to masonry
  • Seals cracks, seams and connection joints
  • Water, temperature and UV-resistant
  • Formulated to stay elastic through all conditions
  • Low odour
  • Solvent-free
Brand Osmo
Drying time hr
Size 310ml
MPN GSE8016, GSE1002, GSE8001, GSE1001, GSE8012, GSE9010
GTIN 6429683733090, 6429683732796, 6429683732864, 6429683732628, 6429683732932, 6429683732550

Osmo Exterior Gap Sealer is a high quality, one component, flexible sealant that has plasto-elastic qualities. It can be used for filling gaps in wood, fixing gaps between masonry, and sealing gaps in door and window frames.

This product can be used in conjunction with the Osmo Gap Sealer Gun Applicator.

Please Note: Osmo Exterior Gap Sealer is not suitable for joints exposed to continuous water immersion.

Ensure that surfaces to be sealed are clean, dry and free from dust, dirt, contamination and loose materials.

Always do a small test area before starting any project to assess compatibility and end result. Follow the manufacturer's instructions on the tube at all times.

  1. Cut dome seal of the tube with sharp knife, taking care not to damage the thread
  2. Screw the nozzle on to the tube
  3. Cut nozzle top at angle to suite size and shape of gap to be filled
  4. Slowly squeeze mastic gun trigger to start flow from nozzle
  5. Apply Osmo Gap Sealer as a continuous bead ensuring contact is made with all faced surfaces
  6. Immediately smooth bead with a flat edge, sponge or wetted finger

Coverage is dependent on gap width and depth but as a guide, based on 3mm gaps a 310ml tube will fill around 30 linear metres.

4 customer reviews
Easy to apply and now have to wait to judge its effectiveness by David Richardson

Easy to use and covers well with paint. Have to now wait to see how it stands up to time and the weather

Reviewed 310ml, White on: 25/01/18
Versatile, flexible and easy to paint over by Mrs Marie Dowdall

I bought this to seal gaps and splits in the wood of an old external balustrade. The product was easy to apply and adhered to both dry and slightly damp wood with no problems, filling even deep splits and joins consistently. Once dry, I overpainted it with a Ronseal external paint, this covered the sealant far better than it did the bare prepared wood. Because it is flexible when dry I expect the sealant to perform well in summer and winter and I expect I won't need to redo the work next year.

Reviewed 310ml, Dark Brown on: 09/09/17
GOOD PRODUCT by Angela Anderson


Reviewed 310ml, White on: 09/09/17
Works Well by Fred Austin

Works like any other exterior sealer. But not as toxic as others. No complaints.

Reviewed 310ml, Pine - Spruce on: 26/09/16