How long can the HDB membrane be left exposed prior to overlaying it with concrete?
Depends on the site conditions and weather conditions, we recommend that you lay the membrane when you see the concrete wagon in the site gates. It can be laid that quickly. The material can be laid in rain, snow etc as long as it is part of a continuous process. I have seen the material left exposed for 4-5 days with out any damage but the longer you leave it the more risk you take. We have a leak free record for the last 13 years so what we have been doing for all of this time must work.
