rendering or knocking down a poorly build outhouse

[suzybare]

ive recently bought an old terrace and it has a poorly built outhouse on the back to use for the washing machine/cold storage-its freezing-poorly insulated too.

it has a lean too roof felted, which im sure is leaking-this is another problems i need to recitify.

it is one brick thick and this has cracks in between the cement. it seems that when it rains hard it comes through onto the walls. it did have plasterboard on the walls but i ripped this off as the damp was coming right through.
without tearing the whole the thing down and starting again is there anything i can do to prevent the rain coming through these cracks and the brickwork. so i maybe able to plasterboard the walls again

such as waterproof glazings? is it PVA
or render plaster on the outside that i can paint over with some outdoor waterproof paint?
i know the roof needs doing and this is a seperate issue but what can be
done to the walls?

any advice is welcome
please reply in laymens terms-im a girl teaching myself DIY so i dont get ripped off and know what the builders will be talking about!!

 

[Mikepeters]

you could clad it with pvc panels (soffit boards for example), render it with lime. use sheet material like roof panels or T&G shed (wood) timber. But if its that bad you could just knock it down and start again.If the roof is bad too, then plasterboard will never be a sucess. there are some waterproofing paints but it sounds past that. Start with the roof and work down.