Do you really need to seal concrete?Yes.
Updated: Sep 1, 2021
When people get their new concrete patios or driveways poured they are often told by the installer or contractor to seal it. What they usually don't get are the details as to why they should seal it, the best concrete sealers to use, the best way to apply it, and specific sealer needs for their new concrete. Getting answers to these types of questions isn’t easy to do when you are shopping at a big building supply store or online. What you usually get is a ton of boastful performance claims and confusing scientific jargon.
Here are some simpler questions and answers about sealing new or old concrete.
What kind of concrete should be sealed? Exterior concrete in any region subject to freeze thaw cycles should be sealed. Freeze thaw regions can be found all over the U.S. from California to Florida and just about everywhere else in between for that matter. In other areas, concrete should be sealed for specific reasons like abrasion & chemical resistance, repellency, dusting, or to simply keep up it's aesthetic appeal.
What will happen if you don’t seal concrete? Concrete is porous by nature and absorbs water and other liquids with little to know resistance at all. In areas with more freezing and thawing the expansion of that frozen water can destroy the surface of unsealed concrete in just a few seasons. If left unsealed, stains from household chemicals, oils, soil & fertilizers and other materials can discolor and even leave permanent damage to the concretes surface.
When do you seal?
Most solvent based acrylic sealers and certain reactive and penetrating sealers like silicates & siliconates can be applied when the fresh concrete can be walked on by the installer without marring the surface. Most other sealers including some acrylics, silanes & siloxanes, urethanes, polyaspartic, and epoxies should only be applied after the concrete reaches 28 days old. Almost all coatings and sealers can be applied after the concrete is 28 days old which is the general time frame to consider concrete fully cured.
Can I DIY concrete sealer?
If you are brave, all sealers can be applied by a do it yourselfer using basic painting tools, such as paint rollers and pump up sprayers but it is always highly recommended that concrete sealers and coatings be installed by professional installers. High performance concrete coatings like moisture cure urethane, 100% solids epoxies, polyaspartics and polyureas will almost always state that they are for professional use only and require professional application tools and professional application techniques.
What kind of sealer should be used? This depends on the type concrete you have and the look you want. Most chemically reactive sealers are non film forming and nearly invisible because they penetrate deep into the concrete and repel water and stains that way, leaving the surface looking very natural. Solvent based acrylic sealers are film forming sealers and deliver color enhancement and different levels of gloss depending on the solids content. Water based acrylic sealers give some color enhancement and usually a satin appearance, also dependent on solids level. Many sealers both water based and solvent based can be tinted semi transparent or opaque with the appropriate color packs. Stamped and other decorative concrete surfaces usually lean towards high gloss sealers where as broom finished and polished concrete surfaces make more use of non film forming and penetrating sealers. Choosing the right sealer really all depends on the end result desired by the end user.