Is it necessary to seal architectural concrete surfaces? We prefer the look of the untreated concrete.
It is not necessary but it is often recommended. It prevents absorption of rain water, which frequently produces a nonuniform appearance of the surface while the concrete is wet and which may over a long period of time produce staining. Sealers also prevent attack from corrosive industrial gases such as sulfur dioxide and they prevent buildup of dirt and smoke deposits. There are some clear sealers whose presence is unnoticeable, or hardly so, from several feet away.