That is disgusting and that your husband allows that kind of crap screams "shit parent" to me. 

Yes, you have every right to go nuclear about nastiness like that in your home. 

It sounds like everything in there is ruined and disgusting anyway, so you could go on with the status quo.  However, I don't think it is unreasonable to expect linens to be washed and a room to be "reset" once every couple years (major gag just thinking of the filth!), even in a skid's room.

What did your husband say when you raised it? 

Most important,  do you have a firm understanding with your husband that Backstabber/Powersulk is OUT at 18 when she finishes high school? That's where I'd spend my time and effort - making sure that happens. 

I'd start making little comments alluding to a smell in the house. then I'd ramp it up until I reached the  point of "hon, we need to do something about that smell coming out of your little poopsiekin's lair. Even the dogs are starting to gag near it." 

I had 5 kids living here and now that they are adults, 4 of them have moved back for various periods with spouses, kids and pets.  I did not and still do not clean for them  (DS and DIL are here often for her medical appts).

I know they had crappy rooms and I know when some lived here as adults, it was sub-par.  I've always had so much other stuff on my plate, I just haven't had the bandwidth to beat my head against this wall.  Plus, frankly, I didn't want to know more about their private habits.  Back in the day, I sometimes hired cleaning help to shovel out.

Did it or does it matter?  As adults, they are all living decently.  As each moved out, I cleaned anyway for the next use of the room.

My experience was that age 18 was no magic date.  I'd hate to see you disappointed if you're counting on big changes then.  Good luck.

That poor lizard. 

Killjoy's room was like that and I didn't care, I couldn't smell anything bad coming from there. I was annoyed that we ran out of certain dishes though, when the policy was no eating upstairs. I got my dishes back when she moved out.

My mother was certifiably insane, but she got a few things right. One of them was "You are responsible for cleaning your own room. It can be messy, but not a biohazard." This means no pet vomit, pet crap, stinky hamster cage, rotting food, spilled drinks. or 2 week old dirty laundry. 

I would suggest enacting these rules. If you are worried about your mattress in there, you can strip the bed and wash the sheets, but leave them in a folded pile on the bed. This way she can get used to putting her own sheets on the bed. Otherwise, I'd let her stew in her own juices. My sd's never left old food in their rooms, and generally kept them clean - except they wouldn't empty their trash (old tissues, maxi pads) and they wouldn't wash their sheets -EVER. The current ones are a year old. The ones at the old house were 3 years old. Gross! I would tell them it helps to prevent allergies if you wash your pillowcases and sheets regularly, but they'd rather be lazy and complain. 

I'd say, once the grossness starts to affect you or your home or your furniture - then its time for them to them to get to cleaning!

If these things were happening in my home, I'd be single. I grew up in poverty but one thing my momma said was, poor don't make us dirty. She kept a clean home and yard and we had chores and were expected to help keep OUR home clean. In my adult life, I raised two kids and their rooms were kept clean, and they both maintained their rooms as they got older. When DHs kids started coming here, that was one of the FEW rules they were to maintain...cleanliness. 

My personal opinion....this is my (ours) house, you having a private bedroom is a privilege.  Act like it. I have no problems going into bedrooms of MY HOME to clean when it's not to my standards. If you don't want me in the room, then make sure when I open the door for "clean check" that is IS CLEAN.

I'm probably the odd ball with this mindset but I don't care. I simply cannot live in nastiness, not to mention the pests that kind of living brings into the home. 

EDIT: I'm not talking about kids being messy as in leaving clothes, toys, books on the floor. My kids were free to be kids but with limits on uncleanliness. No one in this home slept on sheets for two years without washing  them. Or left dishes in their rooms long enough for mold to build up. Wow. I can't even comprehend those things.

I am a clean freak but I managed to raise a messy kid.

She was a messy kid, messy teen and is a messy adult. Not filthy per se just messy. World doesn't end. The way she manages it now, they have a cleaning lady every other  week. It makes a big difference. People find their ways to manage their lives. Llo I was sure my DD would remain messy and she did. But their house looks nice. So that's that. They'll find the way. They enjoy other things in life more than cleaning 

of course if there are bugs crawling outside her door and it smells it's bio hazard. That might need to be cleaned out. By your DH if she refuses 

Aging out isn't a real concept. Even if they move out, they are still your kids. That doesn't change when they turn 18. Most 16-year old kids have no exact plans for what happens after school: local college, out of town, work, army. Too early for definite plans 

I had a bad situation in OSDs room (she was then 12/13 but it started back when she was 11 in our former residence). Basically she was allowed to do what she wanted - ultimate issue was with DH.

BUT that said, once it started to effect me, as in I could smell her room with the door closed while I was on the way to the laundry room, that's when I went in and discovered dirty dishes and utensils, cups/glasses - many moldy. All over the place AND trash everywhere. Her dresser was empty but for more dirty dishes and trash. There was moldy rotting food in containers in her closet, in bags, UNDER a shelf. Her sheets were horrendous (months and months w/out washing).

So I simply gave an ultimatum that if the room wasn't sufficiently cleaned up by X date then I would go in and clean it up myself and no one else then had a say. We have rats in the vicinity, mice, and of course ants and other bugs. NOPE. Not in my home. And I will not live with or around filth. I had to discuss this ONLY with DH - HE got the ultimatum. He did not make sure OSD understood or even talk with her about it. Total avoidance. So I trash bagged everything that wasn't in a reasonable place or looked filthy. I did not clean up her sheets or vacuum. I think I took somewhere between 4-6 bags to the garage, which, per my convo with DH was to be gone through by the two of them and properly sorted - HA!  Didn't happen. She started using those as her personal storage area. So I trashed it all. Eff them. And I did it one more time. And I didn't give two XX's any longer. Still don't regret it.

There is a difference between messy (OK) and filthy (not OK).

Your solution is simple. No WiFi password until her room is cleaned.  I'd also find the pet a new home.  That's ridiculous.  
 

I have a dust allergy and I might close off a room during a cold spell but it still gets dusty and works it's way into the heating system and eventually affects me.  My bd13 knows this and knows I will take the electronics if her room gets out of control.  She has the last of the carpet in the house.  
 

I really think you have a case, and I would suggest this as a father daughter project .  Make the reward for getting it done attractive to both of them. Write your expectations out, a checklist maybe, so they can understand and achieve your goals.  
 

I do wonder just how much more of this crap you can take.  It seems as if you are living below yourself.   

Spawn clean. Regardless of what flavor of spawn or whose spawn they may be.

They get age appropriate chores that they perform. Period. Dot.

These are not compensated nor are they punishment. They are the spawn's contribution to the home and family.

No discussion, no debate. They do it, or they learn the conneciton between poor decisions and escalating abject misery.

It is called... parenting. Or at least a part of parenting.

If we had disrespected our home the way your StepSpawn has, we would have learn the fine trade skills of flooring, carpentry, spackling, painting, laundry, furniture repair, laundry skills, cleaning skills, organizational skills, etc... Our parents would have been so pissed about that disrespect to the home they provided that we would have been restoring the entire structure, the grounds, etc... as an abject lesson in the consequences of idiocy.

Time for daddy to get his heat out of his own ass and put his boot up the ass of his failed family spawn.

Grrr.

I am angry for you.

Make your Spring activity supervising DH and the nasty SD as they restore your home.

Sorry you deal with this Clove. I shut the skids doors too and think hmmm is it time to address the stank room?? I can't understand how some of these young adults/ late teens do not care about their linen? I love the feeling of going into bed with fresh sheets and it's gross knowing all the sweat/dead skin/bacteria live on your linen when you don't wash them.

I think when the skids are of age I'm designating them a wash basket each and placing it infront of their doors and say 'it's linen wash day'. If they want to live in our house and capable of washing their own linen then they can live by our house rules. If they don't I'll tell DH they can't sleep under our roof until they clean their rooms/wash their linen. Go back to BMs sty if you want to live like a pig.

That was how I was brought up. My parents expected me to do my washing and linen and keep my room in a clean state. If I didn't live up to these house hold expectations then I would be looking to move out basically. It taught me how to respect my parents and also myself. 
 

What's hard for us steps is having this expectation backed up by our DHs. If they don't back us up with this then skids are just going to not listen to us and live like pigs. I can't count how many times I used to nag the skids about picking up after themselves. I see their shoes, dirty socks, plates, rubbish, ect on our lounge and I want to clean it asap. Now I throw their shoes and dirty socks out in the hallway right where DH has to step over it. I nag DH now about their dishes and make it his issue which he hates and he tells them off. 
 

Goodluck with the dragons den, lazy teenagers are the worst and I'm dreading having to be firm about the same thing in the future. 

My experience with SD (now 18) I guess would be considered hard-ass right out of the gate. From the minute we bought this house and started living together as "one big happy family" (HA!) I set ground rules. Her bed was to be made every morning and her stuff was to stay in her room and not be strewed all over hte house. Each year as she got older more and more was expected. At first I did her laundry. Then I expected her to do it. I would clean her bathroom. Then she had to start cleaning it herself. 

I made her wash her sheets. Allthough she still only did them like twice a year. With 8 sleepevers a month that equaled every 7 weeks of her sleeping on them they would get cleaned (I do our sheets once every week) 

My attitude was always - My house. My rules. I was lucky inthat DH feels like me and like a neat clean house. 

I believe in things being "sanitary".. but they don't have to be "neat".  So.. a little dust.. fine..  pile of clothes she picks through. fine. she doesn't make her bed.. fine.

Plates with food and glasses half full of soda/juice? not fine.  Animal cages not kept in a healthy state for their residents? not fine.  Unwashed sheets longer than 30 days of residential use (this is fairly extreme. I think10 days if more reasonable for fairly regular use.. or less) or piles of dirty clothes where the smell permeates to outside her room.. Not Fine.

But.. is she expected and does she know how to use the washer? does she have more than one set of sheets.. so she can strip the bed.. make it.. and wash the sheets that were on the bed?  (timing.. she may not have time to go through the whole cycle.).

And.. consequences should be fairly appropriate.. if she is neglecting the cage.. that animal finds a new home.  If she can't keep her room clear of dirty dishes.. she loses permission to eat or drink in her room.  She loses ability to go to friend's house.. use internet.. if her bed isn't stripped and washed.. or if the stench of unwashed clothes comes out of the room.

BUT.. these are not your issues to deal with.. they are her father's.. he needs to care enough about his home..

and.. to be clear... while you are both paying for the home.. he technically is the one whose side is payingfor his daughter.. if you are subsidizing HIM.. that is not her fault.. she is reliant on her father to support her.. she owes you no gratitude for putting a roof over her head.. that is her father's responsibility.. and he should be thanking  you

Yeah we can't expect kids to be grateful for us housing them. That's just a given that they are provided with the place to live. But if you feel you spend too much like buying her things for her room and buying her food and you feel it's too much and you resent it, I'd bring it up with your husband and he'd need to pay for these things. But other than that as a minor child that's where she lives and she doesn't owe gratitude for that. Where else would she live? Its parental obligation to house and feed their children.
 

 But your DH should help more around the house and be grateful when you do things for SD and he should demand she does this or that. Maybe not necessarilly scribbung and declutering cupboards but she needs to be responsible for her room, her pets, her laundry and things like dishes, take trash out etc Dad needs to tell her and if she doesn't listen he needs to deal with it. Not you. Same like it used to be with her grades. Not for you to worry about. Her dad. If he doesn't care, well why would SD care?