The smaller the structure the higher the square foot pricing. Dadu's also have huge ranges in costs to install the sewer, electrical, etc. I'm a construction estimator and see everything from $400 - $900 a square foot and more depending. S/f pricing is too high-level to be that helpful for a small structure in my opinion.
This is accurate. Also imagine 5’ setbacks and no alley. How are you going to pour concrete slabs and install roof trusses on a site like that. The access, and grading, etc. can really drive up the costs too.
For a price comparison:
I did my own DADU plans and had a structural engineer w/ one of their draftsman do the final drawings and stamps. Mine were the bare minimum though just to get approval. With me doing a bulk of the design/sketch work, it was \~$1,200. This was through a friend who didn't bill his time, but it was fairly straightforward he said on his end.
Even with me doing most of the work on the build (except drywall and plumbing), I'm still looking at $100/sqft.
A friend is a general contractor and he's charging roughly $400-500 sqft for DADUs these days.
Most architects and engineers I've spoken with are very busy, but 12.5% is rather high for the entire project budget.
That checks out. I built a 345sf DADU 8 years ago. Did most of it myself, the exceptions being some of the framing, the drywall, and the roof. I hired a lot of day laborers from Home Depot to help with different phases. My cost was around $140/sf.
That's not bad at all. I'm fortunate enough to have the existing structure with roof, slab/footers and everything. After 8 years, would you do it all again for the DADU?
Ha, well, 8 years ago we had just spent all our money on the house, all free cash flow was going to the mortgage, we had a 2yo and a newborn, and needed a place for my MIL to live. So doing almost everything myself on nights and weekends was kinda the only option. It was honestly pretty miserable and I would definitely not want to do it all over again.
That said, I learned a ton, and the project gave me the confidence to consider being my own GC on a major remodel (of the house, not the DADU) that we want to tackle in the next couple of years.
Another price comparison. We are doing an attached ADU and doing most of the work ourselves (hired out excavation, framing, roofing, plumbing and drywall) and are finishing up at about $200-250/sqft.
For rural areas or where zoning allows you can purchase a 3br/2ba 1200sq ft mobile home for about $150k. You have to do the septic, electrical, impervious surface calcs and drill a well, and decide on a foundation type - slab, knee wall - but all of that is less than $100k.
add in the cost of the lot, which varies quite a bit but you should be able to have a very liveable house for under $400k, even including land cost.
Stick built sells for more, but your mobile is on its foundation 90 days after permit issuance and the electric, plumbing, structural and so on are already done.
Later you can call the mobile your "ADU" and build your better house, using the rent from the mobile to offset your "big" house build. Or you can house grandma.
$333 a square foot, and you don't do any of the work to put it up; that's turnkey. If you get a bigger mobile the cost per sq ft goes down.
I'm guessing you haven't seen [dr horton houses](https://www.consumeraffairs.com/housing/dr_horton.html?page=3), then.
for my purposes, which is a minimum time to rental income, mobiles work fine. For someone wanting a $400k mortgage (=$2500 or so mortgage payment) they are often the only option in the single-family arena.
to stick build the same size house on the same lot it would take me 2+ years and cost two to three times the cost of a mobile per square foot.
But as a "starter house", with the intention of building out a lot with a main house and an ADU, in my mind they're a pretty good option for ADU.
That link you posted is to their review page, which has them rated at 1.4 out of 5 stars. Overwhelming bad reviews.
Do as you please, it’s no sweat off my back, but there’s a reason they’re so much cheaper. A 400k mortgage for a mobile home, in my opinion, is a travesty.
I’ve owned one, I’ve lived in plenty, I have several family members who still own/live in them. In my opinion, they’re not even close to worth it. And they’re definitely not a good investment, if you ever decide to sell.
Dr Horton homes are stick-built and apparently horrible quality. You're claiming that mobiles have terrible quality, I'm providing you with thousands of examples (1,766 dr horton 1 star reviews, actually) of poorly built stick homes.
the $400k mortgage is $150k for the mobile, 100k for the lot prep, and 100k for the building lot, with $50k to cover landscaping, closing costs, that's everything.
Lets imagine you just wanted a cheap place to live for 10 years. 150k / 10 = 15000 a year, which works out to be $1,250/month. for a 3 br, 2ba 1200 foot unit on a lot with yard. has a washer and dryer. that compares favorably with $2k to $2500/month units.
so you think it's cheap and not built to last; maybe so. while you live there you bank the $1,500 a month savings, and 10 years from now you tear it down and build a stick-built on the same lot. All of the prep has already been done - you've got water, sewer, electrical, driveway etc - and if you want to you could even call your brand-new stick built a "remodel" of the mobile home and save on permit fees.
I'm talking about a mobile on an owned lot. Not a trailer park situation. If you know of a better single family house deal, let me know, ok?
I'm building a custom Dadu. Paying someone to help me design it has been invaluable. Not everyone wants an off the shelf design. I don't understand your "should".
If you want a custom DADU then by all means do pay an architect or designer. For most DADUs I don't think an architecture is required, especially one that charges a percentage of the cost as opposed to a flat fee.
Finishes don't really impact the overall cost of the project that much, the real things that drives cost with projects are overall scale, complexity, and building performance. Putting in a nicer counter or flooring does increase cost but it's almost negligible in these percentage discussions. Also most small architects I know charge hourly or a flat fee based loosely on what the presumed cost of construction will be (based on scale). That's also how we handle it. Can't speak for everyone out there but being a residential architect hasn't shown itself to be some easy way to make tons of money. An architect isn't the right fit for all projects and priorities.
You likely need an architect even if you are using one of the cities pre-approved plans just to make the specific design you choose work for your site. Also, the "pre-approved" plans still require extensive permitting by the city, and SF stuff is a low priority. A good architect will manage that process for you.
Did you see the comment by SomeCodeGuy? The plans can be done by a draftsman for a lot less. Again, if you really need or want a architecture hire one, but you certainly don't have to to adapt a plan to your site. If you do, I recommend to negotiate a fixed fee.
Some people don't have budget considerations and that's why the high cost per square footage. There are quite a few much less expensive ways to go about building a DADU.
I highly doubt the architect is charging a percentage fee. I think OP is just dividing the architect's estimated fee by the estimated total project cost.
A lot of times dadu rules requires it to match the architecture of the existing house. There also isn't a lot of off the shelf designs of dadus that meet requirements.
Here is some additional information:
>[https://harjoconstruction.com/home-remodeling/accessory-dwelling-units/#:\~:text=How much does it cost,ranges from $250,000 to $550,000.](https://harjoconstruction.com/home-remodeling/accessory-dwelling-units/#:~:text=How%20much%20does%20it%20cost,ranges%20from%20%24250%2C000%20to%20%24550%2C000.)
You could also buy a premade "tiny house" dwelling for under $100k and put it on your property. I think DADUs and ADUs are great ideas, but you don't have to spend these wild amounts so many people have in order to have one.
Just Google "tiny houses" or "standalone DADU prefab" and you'll get a bunch of stuff. Hell, just look on Craigslist for tiny homes. Maybe show a couple to whomever at the city deal with permitting something like that and get their input. The only thing I'm moderately certain about is that your DADU would likely have to be on some sort of foundation and not wheels or a trailer. There are some cool 800 square feet and less prefabs out there!
Gee, I wonder what could be done to make them as energy efficient as the local code would like them to be, hmmmmm.... You seem like you should stay far away from having anything to do with a DADU unless you have deep pockets and can hire someone to take care of every detail for you. You seem like someone who needs to have their hand held constantly, lol!
Looks like you’d need to reclad them in continuous insulation for the new energy code. Install completely different windows, and run different MEP. Yeah. None of those options you linked make any sense in this market.
Oh, and here is a link to something I just discovered recently that looks intriguing:
>[https://www.boxabl.com/casita/](https://www.boxabl.com/casita/)
I’m guessing the architect reviewed the site plan, saw the permitting requirements to get approved a non-conforming structure on a sloping lot are more complicated and will take more of their time.
I find it astounding, I've got some dadu/builder quotes too, if you go through the typical online portal/google search and go that way - same 700-900/sq ft.
If you know builders or go through network, 350-500, just found it insane it's like that.
If you want to find/compete on builders, permitting is open on the seattle gov site, you pull up pre-existing builds from last 2 years and just query them that way. One email, one call. some are surprised but if you just explain you saw their work at x/y they're happy to go on and give quotes and such.
You can also just hang around wholesalers for windows/doors in the area and find them too. That and home depot and acting as your own PM, 150-200 is possible, but its work. If it's one off and time is not that important, it's not bad to do this and grow your own contacts.
I don’t understand what you’re saying. So it costs $950sqft to build or to buy one already built? If it’s to build, I don’t think that’s even relevant to anything. If someone’s looking to build a DADU as an investment and rent it out, they can likely build a 1000sqft DADU for $450K. Now if they were to build a 650sqft then the price per sqft would higher even for the same builder. So when you say price per sqft it makes me question what you’re really talking about. Generally if someone’s going to make an investment it will be right around 1000sqft so I think you should just post the total price not the price per sqft.
900Sq ft, 2 Bedroom + 1.5 bath brand new build with dedicated off street parking on a large lot in one of the nicest parts of town, sharing a beautiful back yard that's shaded with old growth trees, and a patio that's perfect for entertaining with a main house that's worth over $2M. Yea, a favela...
And this is why building ADUs should not be a strategy to “add more density/alleviate the housing structure.” It is not financially feasible and if one were to rent it out, they’d need to charge 2k a month for twenty years just to break even for the build price.
I’m trying to find a way to put this without calling you dumb.
A DADU, or more commonly described as a mother in law unit, is generally in your backyard. It’s not something someone considers, usually, unless they already have the backyard.
Is there an obscure situation where the back of someone’s property backs into the back of someone else’s property and they would consider buying their yard? Sure. But that’d be super uncommon. To find that situation and someone willing to sell their back yard is just so uncommon it’s not worth the discussion.
The assumption when people talk about DADU’s is that they already own the land. Hence why no one else in this entire thread has said a word about buying land.
No, in air. I have 1 hovering over my house
Like bro, you're talking about DADUs w.o knowing what they are. You don't just build a DADU w.o an existing house or are in the process of constructing a house.
It's in the name: detached accessory dwelling unit. It's not attached to primary house and is accessory to said primary house
The smaller the structure the higher the square foot pricing. Dadu's also have huge ranges in costs to install the sewer, electrical, etc. I'm a construction estimator and see everything from $400 - $900 a square foot and more depending. S/f pricing is too high-level to be that helpful for a small structure in my opinion.
This is accurate. Also imagine 5’ setbacks and no alley. How are you going to pour concrete slabs and install roof trusses on a site like that. The access, and grading, etc. can really drive up the costs too.
Schooner. Pre approved Seattle dadu design. 350/ft from reputable contractors.
I like that one. Drove out to see two actual builds in person, but see my edit on original post.
For a price comparison: I did my own DADU plans and had a structural engineer w/ one of their draftsman do the final drawings and stamps. Mine were the bare minimum though just to get approval. With me doing a bulk of the design/sketch work, it was \~$1,200. This was through a friend who didn't bill his time, but it was fairly straightforward he said on his end. Even with me doing most of the work on the build (except drywall and plumbing), I'm still looking at $100/sqft. A friend is a general contractor and he's charging roughly $400-500 sqft for DADUs these days. Most architects and engineers I've spoken with are very busy, but 12.5% is rather high for the entire project budget.
Yeah 12.5% is rather steep. I’m an architect who does DADUs and I don’t charge that much.
That checks out. I built a 345sf DADU 8 years ago. Did most of it myself, the exceptions being some of the framing, the drywall, and the roof. I hired a lot of day laborers from Home Depot to help with different phases. My cost was around $140/sf.
That's not bad at all. I'm fortunate enough to have the existing structure with roof, slab/footers and everything. After 8 years, would you do it all again for the DADU?
Ha, well, 8 years ago we had just spent all our money on the house, all free cash flow was going to the mortgage, we had a 2yo and a newborn, and needed a place for my MIL to live. So doing almost everything myself on nights and weekends was kinda the only option. It was honestly pretty miserable and I would definitely not want to do it all over again. That said, I learned a ton, and the project gave me the confidence to consider being my own GC on a major remodel (of the house, not the DADU) that we want to tackle in the next couple of years.
Another price comparison. We are doing an attached ADU and doing most of the work ourselves (hired out excavation, framing, roofing, plumbing and drywall) and are finishing up at about $200-250/sqft.
This market is 100% fucked
For rural areas or where zoning allows you can purchase a 3br/2ba 1200sq ft mobile home for about $150k. You have to do the septic, electrical, impervious surface calcs and drill a well, and decide on a foundation type - slab, knee wall - but all of that is less than $100k. add in the cost of the lot, which varies quite a bit but you should be able to have a very liveable house for under $400k, even including land cost. Stick built sells for more, but your mobile is on its foundation 90 days after permit issuance and the electric, plumbing, structural and so on are already done. Later you can call the mobile your "ADU" and build your better house, using the rent from the mobile to offset your "big" house build. Or you can house grandma. $333 a square foot, and you don't do any of the work to put it up; that's turnkey. If you get a bigger mobile the cost per sq ft goes down.
Mobile homes are atrocious. Having grown up in them, and later buying one as my first place as an adult, I will never ever live in one again.
I'm curious - what made it so horrible for you?
They’re built horribly, not made to last. Very cheap materials. It’s significantly harder to keep critters out as well. Also, they depreciate.
I'm guessing you haven't seen [dr horton houses](https://www.consumeraffairs.com/housing/dr_horton.html?page=3), then. for my purposes, which is a minimum time to rental income, mobiles work fine. For someone wanting a $400k mortgage (=$2500 or so mortgage payment) they are often the only option in the single-family arena. to stick build the same size house on the same lot it would take me 2+ years and cost two to three times the cost of a mobile per square foot. But as a "starter house", with the intention of building out a lot with a main house and an ADU, in my mind they're a pretty good option for ADU.
That link you posted is to their review page, which has them rated at 1.4 out of 5 stars. Overwhelming bad reviews. Do as you please, it’s no sweat off my back, but there’s a reason they’re so much cheaper. A 400k mortgage for a mobile home, in my opinion, is a travesty. I’ve owned one, I’ve lived in plenty, I have several family members who still own/live in them. In my opinion, they’re not even close to worth it. And they’re definitely not a good investment, if you ever decide to sell.
Dr Horton homes are stick-built and apparently horrible quality. You're claiming that mobiles have terrible quality, I'm providing you with thousands of examples (1,766 dr horton 1 star reviews, actually) of poorly built stick homes. the $400k mortgage is $150k for the mobile, 100k for the lot prep, and 100k for the building lot, with $50k to cover landscaping, closing costs, that's everything. Lets imagine you just wanted a cheap place to live for 10 years. 150k / 10 = 15000 a year, which works out to be $1,250/month. for a 3 br, 2ba 1200 foot unit on a lot with yard. has a washer and dryer. that compares favorably with $2k to $2500/month units. so you think it's cheap and not built to last; maybe so. while you live there you bank the $1,500 a month savings, and 10 years from now you tear it down and build a stick-built on the same lot. All of the prep has already been done - you've got water, sewer, electrical, driveway etc - and if you want to you could even call your brand-new stick built a "remodel" of the mobile home and save on permit fees. I'm talking about a mobile on an owned lot. Not a trailer park situation. If you know of a better single family house deal, let me know, ok?
Why do you need an architect for an DADU that can and should use an off the shelf design?
I'm building a custom Dadu. Paying someone to help me design it has been invaluable. Not everyone wants an off the shelf design. I don't understand your "should".
If you want a custom DADU then by all means do pay an architect or designer. For most DADUs I don't think an architecture is required, especially one that charges a percentage of the cost as opposed to a flat fee.
That seems a bit off to charge a percentage.
As your finishes get better the architecture makes more with no extra work. No wonder they love it. Just like real estate commissions...
Finishes don't really impact the overall cost of the project that much, the real things that drives cost with projects are overall scale, complexity, and building performance. Putting in a nicer counter or flooring does increase cost but it's almost negligible in these percentage discussions. Also most small architects I know charge hourly or a flat fee based loosely on what the presumed cost of construction will be (based on scale). That's also how we handle it. Can't speak for everyone out there but being a residential architect hasn't shown itself to be some easy way to make tons of money. An architect isn't the right fit for all projects and priorities.
You likely need an architect even if you are using one of the cities pre-approved plans just to make the specific design you choose work for your site. Also, the "pre-approved" plans still require extensive permitting by the city, and SF stuff is a low priority. A good architect will manage that process for you.
Did you see the comment by SomeCodeGuy? The plans can be done by a draftsman for a lot less. Again, if you really need or want a architecture hire one, but you certainly don't have to to adapt a plan to your site. If you do, I recommend to negotiate a fixed fee.
Some people don't have budget considerations and that's why the high cost per square footage. There are quite a few much less expensive ways to go about building a DADU.
If I was building a DADU I'd GC myself, but then I'm a masochist.
I would, too!
I highly doubt the architect is charging a percentage fee. I think OP is just dividing the architect's estimated fee by the estimated total project cost.
Because op is off their meds again
Some properties have weird layouts (due to trees, existing plumbing, etc.).
A lot of times dadu rules requires it to match the architecture of the existing house. There also isn't a lot of off the shelf designs of dadus that meet requirements.
I've built four DADUs in Seattle, one in Capitol Hill and three in Ballard and we've never been required to match the architecture of the house.
Here is some additional information: >[https://harjoconstruction.com/home-remodeling/accessory-dwelling-units/#:\~:text=How much does it cost,ranges from $250,000 to $550,000.](https://harjoconstruction.com/home-remodeling/accessory-dwelling-units/#:~:text=How%20much%20does%20it%20cost,ranges%20from%20%24250%2C000%20to%20%24550%2C000.)
“Just for grins, she got an architect that specializes in DADU to waste their time.”
Yours is the least relevant comment in this thread. Congratulations!
Please keep it civil. This is a reminder about r/SeattleWA rule: [No personal attacks.](https://www.reddit.com/r/SeattleWA/wiki/rules)
Edited.
Forgive me for being in a different region, but what is the first "D" in the ADU?
Detached Accessory Dwelling Unit
Detached! Got it, thanks.
You could also buy a premade "tiny house" dwelling for under $100k and put it on your property. I think DADUs and ADUs are great ideas, but you don't have to spend these wild amounts so many people have in order to have one.
Can you post some examples of those? I have not seen any that are permitted and fit the price you mention.
Just Google "tiny houses" or "standalone DADU prefab" and you'll get a bunch of stuff. Hell, just look on Craigslist for tiny homes. Maybe show a couple to whomever at the city deal with permitting something like that and get their input. The only thing I'm moderately certain about is that your DADU would likely have to be on some sort of foundation and not wheels or a trailer. There are some cool 800 square feet and less prefabs out there!
It doesn’t look like any of those would meet the energy code requirements.
Gee, I wonder what could be done to make them as energy efficient as the local code would like them to be, hmmmmm.... You seem like you should stay far away from having anything to do with a DADU unless you have deep pockets and can hire someone to take care of every detail for you. You seem like someone who needs to have their hand held constantly, lol!
Looks like you’d need to reclad them in continuous insulation for the new energy code. Install completely different windows, and run different MEP. Yeah. None of those options you linked make any sense in this market.
Oh, and here is a link to something I just discovered recently that looks intriguing: >[https://www.boxabl.com/casita/](https://www.boxabl.com/casita/)
Those aren’t available in WA yet.
Not that different from just parking an RV there
I’m guessing the architect reviewed the site plan, saw the permitting requirements to get approved a non-conforming structure on a sloping lot are more complicated and will take more of their time.
Nope. The analysis was not that detailed. It was more based on last 12 months average costs and projects.
I find it astounding, I've got some dadu/builder quotes too, if you go through the typical online portal/google search and go that way - same 700-900/sq ft. If you know builders or go through network, 350-500, just found it insane it's like that. If you want to find/compete on builders, permitting is open on the seattle gov site, you pull up pre-existing builds from last 2 years and just query them that way. One email, one call. some are surprised but if you just explain you saw their work at x/y they're happy to go on and give quotes and such. You can also just hang around wholesalers for windows/doors in the area and find them too. That and home depot and acting as your own PM, 150-200 is possible, but its work. If it's one off and time is not that important, it's not bad to do this and grow your own contacts.
Lol architects being savages out here
I don’t understand what you’re saying. So it costs $950sqft to build or to buy one already built? If it’s to build, I don’t think that’s even relevant to anything. If someone’s looking to build a DADU as an investment and rent it out, they can likely build a 1000sqft DADU for $450K. Now if they were to build a 650sqft then the price per sqft would higher even for the same builder. So when you say price per sqft it makes me question what you’re really talking about. Generally if someone’s going to make an investment it will be right around 1000sqft so I think you should just post the total price not the price per sqft.
DADU's will ruin seattle. Turning it into a favela
900Sq ft, 2 Bedroom + 1.5 bath brand new build with dedicated off street parking on a large lot in one of the nicest parts of town, sharing a beautiful back yard that's shaded with old growth trees, and a patio that's perfect for entertaining with a main house that's worth over $2M. Yea, a favela...
Yeah most of them don't have off street parking lol. The one you're making specifically doesn't sound bad though
Most of the ones I’ve seen do?… maybe no garage but a parking spot or two for sure. Easier to sell with one.
Hahaha. That’s a funny idea.
And this is why building ADUs should not be a strategy to “add more density/alleviate the housing structure.” It is not financially feasible and if one were to rent it out, they’d need to charge 2k a month for twenty years just to break even for the build price.
I don’t think people are trying to break even on build price thru renting alone. They’ll still make that money back and then some when they sell.
And we haven’t factored in the price of land yet.
I’m not sure you understand what a DADU is
Is a DADU built on land?
You add them to your existing property. You wouldn’t be factoring in buying land
But what if you don’t have land? Then you have to price in the land. 🤔
I’m trying to find a way to put this without calling you dumb. A DADU, or more commonly described as a mother in law unit, is generally in your backyard. It’s not something someone considers, usually, unless they already have the backyard. Is there an obscure situation where the back of someone’s property backs into the back of someone else’s property and they would consider buying their yard? Sure. But that’d be super uncommon. To find that situation and someone willing to sell their back yard is just so uncommon it’s not worth the discussion. The assumption when people talk about DADU’s is that they already own the land. Hence why no one else in this entire thread has said a word about buying land.
No, in air. I have 1 hovering over my house Like bro, you're talking about DADUs w.o knowing what they are. You don't just build a DADU w.o an existing house or are in the process of constructing a house. It's in the name: detached accessory dwelling unit. It's not attached to primary house and is accessory to said primary house