Why the need for Gap Filler Sealants

Gap filler construction sealants are used regularly in industrial and construction applications. We try and explore why is the gap is created and why do we need to seal it.

Why is the gap created: 

Industrial : gaps between flanges due to surface irregularities, Engineering tolerances. When two surface of best machined flanges are mated, metal to metal contact is  < 40%. gap filler This is due to crest and troughs on the machined surface not visible to naked eye. These micro gaps become potential leak path in future. Hence such gaps needs to be sealed with a suitable sealant.  Anaerobic adhesive is suitable for machined flanges and silicone sealant is better for cast or sheet metal flanges. 

Construction applications

  • Gap between window frame and concrete wall: Difference in designed dimensions and manufactured dimensions. 
  • gap between PU panels: gap is maintained by design for easy installation and maintenance
  • Gap between core cut holes and utility pipes, trays, wires etc. 
  • Gap between Door frame and Concrete wall

Why do we seal these Gaps? 

To stop entry of water, atmospheric air, polluting atmospheric gases, sound  insulation, electric insulation, water proofing etc.

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Gap filler Sealants vs traditional gap filling methods. 

Traditional Gap filling methods
  • White cement
  • Mixture of cement + sand slurry
  • plaster of Paris
  •  crack filler powder
  • bituminous tape
  • Thermocol
Problems with traditional technology
  • mixing with water required to prepare the paste 
  • paste is applied manually, it is cumbersome and time consuming ( high labour cost)
  • after drying the sealing material becomes hard and inflexible, it cracks and creates leak paths 
  • total cost is more than Supex sealants 

Sealant selection procedure

Factors to be considered while selecting gap filler sealant.
  • Gap between  the joints in mm
  • Flexibility of the joint depending upon if it is subjected to expansion/ contraction
  • Exposure to external environment . Viz : Sunlight – is it UV resistant 
  • Chemical resistance : exposure to corrosive chemicals, acids, fuels etc
  • Temperature to be sustained by the assembly
  • Expected life of the joint : sometimes sealant is used temporarily to hold parts together
  • Paintibility – can  it painted over
  • Cost
  • Ease of application

Which sealant to use ?


Silicone( Neutral)



Hybrid MS

Gap in mm










Bond strength





Environment/ Weather resistance










Wet Surface/ rains



          Property Required               Sealant technology preferred   

  1. High Gap                                    PUF, PU, MS 
  2. High flexibility                         Silicone, PU, MS 
  3. High Bonding strength         MS 
  4. High Weather resistance      Silicone, MS 
  5. Lowest cost                               Acrylic       

Gap Filler Sealant Foam ( PUF)

Pre-polymer is packed in 750 ml aerosol can with a carrier agent. An adopter ( straw pipe) is screwed onto the tip of can, shaken 15-20 times, inverted upside down and press lever. Liquid foam comes out under pressure and expands upon contact with atmosphere. It expands and cures ( dries) by reacting with the atmospheric moisture into ‘ thermocol’.  This cured PU foam provides sound insulation, electrical insulation, water resistance, 100% sealing and bonding, heat insulation. 

It is used by various industries including construction, solar, industrial, HVAC and etc. 

FR Pu foam is fire retardant too. B1 FR PUF provides 120 minutes of fire retardancy. 


  • High gap filling capability > 2 inches
  • High coverage- low application cost
  • Insulates against electricity, Sound, Water, heat- verastile product

gap filler sealant Pune Typical Products: Supex 100 PUF Straw grade, B1 FR PUF Anaghafoam FR  

Gap filler Sealant Foam

Supex 100 Straw type PUF

Gap Filler sealant FR Foam

Anaghafoam FR foam Spray

Window gap filling sealant- Interior & Exterior

uPVC Window Installation: Gap between upvc window and concrete wall is filled with Supex Sealants.

  • Gap upto 5-6 mm: Supex 500 acrylic paintable GP sealant. 
  • Gap > 5 mm: Apply Supex 100 PU foam to fill maximum gap then apply Supex 500 as a top coat ( approx 2 mm). Max gap is filled with PUF while the top coatof acrylic sealant protects the PUF below and barrier to entry of moisture, environment, rain etc. 

Aluminium window / channel installation: Seal gap between granite and aluminium channel or Al. channel and concrete wall  with Acrylic General purpose white paintable sealant. Supex 500.  

High gap filling : Fill up with PU foam with Supex 100 PUF first, then apply top coat with Supex 500 acrylic paintable sealant.

Regular gap filling: Supex 500 paintable acrlyic sealant.

Gap filler sealant

Supex 500 gap filler seaalnt for doors and windows

External weather sealing

Supex 501

Gap filler for External & Internal wall cracks

crack filler

stop leakageExternal walls– use Supex PU 25, high strength | High gap fill | High elongation | Paintable | Long life Polyurethane sealant

Advantages of Supex PU 25 over than crack fillers 

  • ready to use, no mixing with water etc required.
  • can be applied with a gun, so application and quantity control is better
  • flexible, elongation > 400% 
  • paintable
  • Long life

Internal Walls– Use Supex 501, flexible | paintable | doesn’t crack when exposed to varying climate | cost effective upvc window silicone sealant

Advantages of Supex 501 vs plaster of paris, white cement, putty 

  • doesn’t crack with time, remains flexible after drying too
  • ready to use , no mixing required
  • applied with a gun, better control and easy application
  • paintable
  • long life- much better than white cement, putty or plaster of paris.
  • high bonding strength.

Waterproof Gap Filler

Terrace floor cracks, hairline cracks on beam, column or pillars- Supex MS construction sealant 603UV 

Benefits of Supex 603UV over regular/ traditional sealants gap filler

  • Excellent weather resistance, long life
  • high gap filling
  • high elongation and high strength too 
  • paintable
  • bonds all building material without primer

Gap Filler for Doors/ Door Sealant

Traditional method: Use white cement to fill the gap between wall and door frame. Application is cumbersome and manual, high labour cost. Yet, with time white cement tends to crack and looses its adhesion strength

Solution: Apply PU foam spray sealant to fill the gap between wall and frame. High strength, permanent gap fill, no cracks, low cost. 

  • Supex 100 PUF straw and Gun grade
  • Anaghafoam FR- Fire retardant B1 approved 

Gap filler sealants at best price

Call on 18001214771 for enquiry or click here to contact online
Gap filler adhesive and sealant
Article Name
Gap filler adhesive and sealant
Gap filler sealant is used regularly in industrial and construction applications, it is used to stop entry of water, atmospheric air, polluting atmospheric gases, sound insulation, electric insulation, water proofing etc. Gap between Door frame and Concrete wall, core cut holes and utility pipes, trays, wires
Publisher Name
Anagha ASF LLP
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