Stop my dog peeing in the house?

hiya we have a 3 year old black lab called Sirius he's a typical 3yr old lab as in hyper and daft as a brush. unfortunately he has this habit we cant seem to break that is he pees in the house. its not as if its only if hes left in the house for hours. which hes not. but literally sometimes he will pee 30seconds after hes entered the house. he is house trained and generally is fine but id say we have a puddle once a week. any sugestions. i googled it and found these things called belly bands but they look a bit cruel.