How do I weatherproof my TARDIS?

[Dematerialiser]

The main thing to remember with any outdoor Tardis is that where there's a joint between areas of the build the water will get in. This includes all the obvious horizontal areas like the roof, but more unexpected areas too. Where you have to have a gap or join which can't be sealed using weatherproof filler (car body filler or special outdoor wood repair filler) one of the best methods to use is an outdoor-rated silicone sealant. If you're worried about only being able to find black, white, clear or opaque (and the whole thing looking grim once any paint you put on top of it washes/chips off) you can buy coloured sealants from online specialists. Using a blue which may be close to your final paint choice may help it weather more gracefully.

Literally underneath all this is what you really need to look after: the wood itself. Use a good weatherproof paint system - one which comes with a precoat to seal the wood from taking on moisture, and then an undercoat that's designed to bond with the topcoat is probably best. Test it on a piece of spare wood from your build beforehand to make sure. And don't mix different paint systems - the paint might start to dissolve!  

Some builders worry about the roof of their Tardis, designing slopes into the signboxes and lower roof stages to encourage water to roll off instead of sit around. Others have even coated the whole lot in liquid rubber (the vapours from that really can send you into outer space - use at your peril!). The main thing though is that, if you've sealed all the gaps, used a decent paint system (precoat and undercoat) and used plenty of coats you should be okay. As with any outdoor building, you should inspect and repair at least once a year if you want it to last.

If possible your Tardis base shouldn't be in contact with damp surfaces - planting the box in a field sounds like a nice dramatic idea but without a concrete base and some damp-proof membrane the thing will rot from the ground up in no time. One way of preventing this is to place the box either on decking or, if on slabs or conrete, by raising the box onto bearers of some kind - just enough to let the air circulate underneath.

Happy weatherproofing (is that actually possible??)