I am building under a roof, but still outside. I have been suprised by the humidity effect on Titebond. I thought it was the glue, but had the same results with Franklin and Elmers. Then I thought it was the wood. Then the weather cleared and everything works. A scarf done on a humid day can take up to 36 hours; 4 hours works on a crisp day. In the end, they all seem strong.