What is PU? The chemical name of PU is polyurethane. In general, most PU waterproof materials in Taiwan are green and often applied to roof waterproof. In chemical, this type of material is good for waterproof and many foreign companies still produce such waterproof materials.
Why PU waterproof in Taiwan fails all the time? The reasons are nothing more than followings:
1. The surface is not clean—the floor must be clean before applying waterproof coating and avoid dust and loose substance as much as possible, otherwise the adhesion could be bad.
2.The floor is moist—since PU is an solvant-based waterproof material, the roof must be dry before applying. Otherwise, the moist would be covered inside after finishing waterproof construction and result in peeling of PU waterproof coating by vapor with strong power converted from sunshine.
3. PU waterproof coating is too thin —PU waterproof coating must be thick enough to be waterproof. Because PU itself still has lower water absorption, the rain may penetrate PU waterproof coating to the floor through consecutive heavy rain if it is not thick enough. With sunshine in good weather, the water absorbed in the bottom would convert into vapor and result in peeling of waterproof layer.
4. Inferior material—due to price competition of waterproof materials, many PU materials manufacturers in Taiwan would do shoddy work and use inferior material that reduce physical property of waterproof material and result in failure of waterproof.
5. Insufficient construction experience --it is better that professional contractors do the work instead of applying waterproof materials purchased randomly from painting shop. It is necessary to carefully determine the cause of leakage before construction and settle it. Therefore, though PU waterproof layer is not permanent effective, it is still certain waterproof duration.
If you lack confidence in polyurethane, you can try to use MICSIL 170 to replace PU.

The exposed waterproof coating (e.g.: PU coating, acrylic coating...etc) basically has advantage of cheap and convenient application. However, it usually fails due to insufficient experience of environment judgment, while the major reason is that declining of any waterproof material would be accelerated if directly exposed to UV and other natural damage. The fact of waterproof material aging still exist no matter how good the material is. The life of waterproof coating could be prolonged if it is covered after waterproof application. That is why some old buildings with waterproof materials covered after completion of asphalt waterproof application has no leakage problems over one or two decades. Notwithstanding the disadvantage of expensive construction costs, coverage of waterproof coating is still worthy from long-term economic effect perspective.