Concrete Joint Sealant Types – what to use and when to use it.

Concrete joint sealant types


There’s a huge range of products on the market that can be used to seal concrete joints – so it can be difficult to know which one to use. We generally use elastic sealants rather than mortars or other types of mastic on our projects as most of the joints we seal are in walls, not floors.

We wanted to give you an idea of the types of sealants we use with our products for common applications. If you need any help or would like prices for any of these products, get in touch.

The sealants listed below are Polyurethane based and perform differently to silicone sealants that you’d usually used for a domestic job – like sealing around a bath or window.

We use Sika® Everbuild sealants on our retaining wall jobs. We find their products are easy to use, reasonably priced and they have excellent technical support.


Mastic Applications

In the table below, you’ll find some common applications that our precast products are used for. For each type of project, we’ve highlighted which products can be used to seal the concrete joints.

Sikaflex® PRO-3 Sikaflex® TS Plus EverBuild Hybriflex FR Sikadur® Combiflex
Indoor X X X X
Outdoor X X X X
Livestock Building X
Grain Store Walls X
Silage Clamp Walls X X
Slurry Store Walls X X
Slurry Channels X
Bund Walls X X
Flood Defence Walls X X
Grit Salt Walls X
Waste & Recycling Walls X X
Fire & Blast wall X
Temporary Oil & Fuel Resistant X X X
Sewage Treatment Plants X X X

Concrete Joint Sealant Preparation

If you need more information about sealing concrete joints, you should read the – How to seal precast concrete joints article, which gives you a step-by-step guide.

It’s important to know that concrete joints need to be prepped before you seal them – there are two products that you’ll need for this:

  • Primer – Sika® Primer-3 N
  • Joint backer rod – 15mm diameter Sika® closed-cell Polyethylene

The concrete primer will ensure that the sealant will bond properly to the concrete and the foam backing rod will reduce the amount of sealant needed. The Primer-3 N come in 1 Litre bottles – you should be able to prime around 40m of joints per bottle. The foam backer rods come in 550m rolls.

In the past, expanding polyurethane foams were used to fill the gap between precast units and in concrete slabs. We’ve found that the foam rods are much quicker and easier to apply and work better with the movement in the walls.


Precast Concrete Tanks

Mastic Sealant Calculator

The table below will give you an idea of the amount of concrete joint sealer you would need for a project. We’re focusing on wall joints in this article – however, the same principle can be used for construction and expansions joints in concrete floors.

As a guide – the depth of mastic needed is usually 1/2 of the joint width e.g. if you have a 10mm wide gap, then the depth should be approximately 5mm. When we are pricing projects we normally allow 1 x 600ml sausage for a 5-metre long joint.

Mastic Sealant Calculator (600ml Foil) – Approx. metres of mastic per 600ml

Joint Width (mm)

Joint Depth (mm) 3 6 8 10 12 15 18 20 25 30
3 66 33 25 20 16.5 13 11 10 8 6.5
6 33 16.5 12.5 10 8 6.5 5.5 5 4 3
8 25 12.5 9 7.5 6 5 4 3.7 3 2.5
10 20 10 7.5 6 5 4 3 3 2.5 2
12 16.5 8 6 5 4 3 2.5 2.5 2 1.5
15 13 6.5 5 4 3 2.5 2 2 1.5 1
18 11 5.5 4 3 2.5 2 1.5 1.5 1 1
20 10 5 3.5 3 2.5 2 1.5 1.5 1 1
25 8 4 3 2.5 2 1.5 1 1 1 1

Sikaflex® PRO-3

Description: Sikaflex® PRO-3 is a 1-component, moisture-curing, elastic joint sealant with high mechanical and chemical resistance.

Chemical Base: i-Cure® Technology polyurethane

Packaging: 600 ml foil pack, 20 foil packs per box

Colour: Concrete Grey


  • Movement capability of ± 35% (ASTM C 719)
  • Very high mechanical and chemical resistance
  • Bubble-free curing
  • Good adhesion to most construction materials
  • Solvent-free
  • Very low emissions

Get more info on Pro-3 or download the product datasheets from the Everbuild website >


Sikaflex® TS Plus

Description: Sikaflex® TS Plus is a 1-part, moisture curing, elastic sealant that is resistant to liquid manure and suitable for sealing domestic sewage systems.

Chemical Base: Polyurethane

Packaging: 600 ml foil pack, 20 foil packs per box

Colour: Concrete Grey


  • Movement capability of 15% (ISO 9047)
  • Resistant to domestic sewage, liquid manure and numerous chemicals
  • High tear strength
  • High modulus

Download the product datasheet for TS Plus >


EverBuild Hybriflex FR

Description: Hybriflex FR is a one-part, chemically curing solvent-free sealant and adhesive combining the best qualities of silicone and polyurethane technologies. It has a fire rating of up to 4 hours in certain joint configurations (when tested to EN1366 Part 4 2006 – Warrington Fire Certificate 195854/A October 2010).

Chemical Base: N/A

Packaging: 600 ml foil pack, 20 foil packs per box

Colour: Concrete Grey


  • Good slump resistance
  • Abrasion-resistant
  • Excellent resistance to Chemicals & petrol (10% dilute acids, alkalis, most solvent)
  • Good flexibility (±20%- façade)
  • Over paintable with most paints (compatibility test should be made prior to full-scale application)
  • Can be applied on damp/wet surfaces
  • Non-hazardous to health

Find out more and download the Hybriflex product datasheet from the Everbuild website >



Description: Sikadur-Combiflex® is a high-performance joint sealing system for construction, expansion and connection joints as well as for cracks. The system allows irregular and high movement in more than one direction, whilst maintaining a high-quality seal.

Chemical Base: The Sikadur-Combiflex® system consists of a modified flexible Polyolefin (FPO) waterproofing tape with advanced adhesion and a range of suitable Sikadur® adhesives. Adhesives are solvent-free, thixotropic two-part adhesives based on epoxy resins and fillers.

Packaging: Varies

Colour: N/A


  • Advanced adhesion, no activation on-site required
  • Easy to install
  • Suitable for both, dry and damp concrete surfaces
  • Extremely flexible
  • Performs well within a wide range of temperatures
  • Excellent adhesion to many materials n Weather and water-resistant
  • Available with normal and rapid hardening grades of adhesive
  • Good resistance to many chemicals
  • Root resistant

Find out more about the Combiflex system from the Sika waterproofing website >


Mastic Application Service

Our installation services include joint sealing – speak to the team If you’d like more information or a quote for an upcoming project.