Tip for the builders?

[PintOfBovril]

We're having a summer house built in our garden and the team of builders are amazing. Polite, tidy, friendly and ahead of schedule thanks to some incredibly hard work in very rainy conditions. Obviously we're paying the company they work for but should we give them an extra 'tip'? Money? Beers? I feel like they've gone above and beyond what we were expecting.

I've bought a box of beers in the past - seemed gratefully received.

A box of beers is a nice touch, you could also send a message to the building company saying what they did that was so helpful to you, so they are valued by their company. A raise for being an excellent worker will be worth even more to them than some beers.