Is this crack serious?

[LC3]

I've not long moved into a new flat and I've been redecorating. There's a fair few minor cracks I've fixed myself but there's two that have me worried, and perhaps needlessly. Hoping to get some advice as to whether they're just unsightly and I can fill them myself with some advice, or if I need to get someone to look at it.

I've uploaded some pictures here: http://www.boatsandbirds.net/wallcrack/. Excuse the poor quality, they were taken with my BlackBerry.

The flat is on the first floor but the cracks are in the small ground floor area where my front door is. The wall is high and the cracks appear to be bulging. The cracks vary from hairline to just under a cm wide. The flat is one of four in an old sandstone building, there seems to have been some movement as I said there're other cracks and the door frames were a little warped (had to adjust the hinges to get the doors to shut properly) but I've only been in a few months so I don't know anything of the history.

I'm pretty handy at fixing small cracks but it seems the only way for me to fill these ones would be to hack out the bulging plaster to make the wall surface flat again, and fill slowly in layers... but I don't want to do that without knowing for sure that they're normal cracks, as this is a rented property. I rent from a housing association who state the tenant is to see to cosmetic cracks, so... are they cosmetic?

[stoneyboy]

LC3,
They look way beyond cosmetic cracks to me.
Push the housing association to get their surveyor in to examine them. Don't try any repairs yourself at this time.
end

[30yearsinthegame]

Hi mate

Just seen your pictures. Its hard to say what type of crack it is untill you hack some off and check the brickwork. If the brick work has craked then it could be structual. Or it could be two different services behind where the plasterer has not used eml (metal lath) get some one out to check this out. Come back and let us all know. Good luck