Should I build a basement ADU?
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Mechanicsburg, PA · Member since 2013 · 3k+ posts · 2k+ votes
1y@Bob Ross There are 3 different aspects to consider. One is legal around here some local governments don't allow ADU at all, some have restrictions like the ADU can only be rented to a relative like a "mother in law suite", one local rule is that it must be attached to the primary dwelling, and some areas have few if any restrictions.
Second issue is "basement" units or even basement bedrooms. Most codes require egress windows in all basement bedrooms and all basement units. Not a problem if your basement is above grade. But if your basement is below grade, constructing an egress window is costly. By definition an egress window must allow free passage through the window, when opened for a fire fighter fully equipped including with air tank. There are requirements for the size of the opening as well as the maximum window sill height. (must be low enough that a child could climb without a stool or ladder inside.) Most basement windows are way too small and way to high to meet code.
The third issue involves return on investment. I've bought and sold over 1,000 properties for my own inventory and have NEVER finished a basement. I've owned properties that had basements finished by prior owners. Standard Appraisal requirements are that basement square footage is NOT to be counted in the building square footage if any part of the basement is below grade. If on 3 side the basement is fully above grade and on the 4th side is even only 1 foot below grade the basement finished space is not added to the square footage of the building. While the footage is NOT added, there is value added for finished space below grade. In reality basements are often dark, musty, moldy, damp and water prone, which makes them less desirable to the buying public. imho, be cautious on how much you spend, because your return on investment of below grade space may be less than you expect.
9 Replies
I can’t give you a Boston specific answer. In Las Vegas it can be called a mother-in-law suite or as DR Horton advertises it a “Next Gen Suite”. They charge an extra $30k. But it’s still a single home with the total beds/baths. This is all assuming the suite gets its own entrance. If it can have its own laundry that’s another bonus.
You can either put a regular door between them if you don’t plan to rent it out. Otherwise you either put a door with two locks one on each side (like a hotel suite), two doors each with a lock on their side, or if money is tight just a lock on the suite’s side.
Ps. Make sure it’s allowed. Many people have posted about buying homes where a second kitchen was added and they had to tear it out.
- Member since 2019 · 14 posts · 13 votes1y
Check with zoning first, for example in my town they didn’t allow a shower in my basement bathroom because they thought i was gonna rent out the space on a single family.
- Mechanicsburg, PA · Member since 2013 · 3k+ posts · 2k+ votes1y
@Bob Ross There are 3 different aspects to consider. One is legal around here some local governments don't allow ADU at all, some have restrictions like the ADU can only be rented to a relative like a "mother in law suite", one local rule is that it must be attached to the primary dwelling, and some areas have few if any restrictions.
Second issue is "basement" units or even basement bedrooms. Most codes require egress windows in all basement bedrooms and all basement units. Not a problem if your basement is above grade. But if your basement is below grade, constructing an egress window is costly. By definition an egress window must allow free passage through the window, when opened for a fire fighter fully equipped including with air tank. There are requirements for the size of the opening as well as the maximum window sill height. (must be low enough that a child could climb without a stool or ladder inside.) Most basement windows are way too small and way to high to meet code.
The third issue involves return on investment. I've bought and sold over 1,000 properties for my own inventory and have NEVER finished a basement. I've owned properties that had basements finished by prior owners. Standard Appraisal requirements are that basement square footage is NOT to be counted in the building square footage if any part of the basement is below grade. If on 3 side the basement is fully above grade and on the 4th side is even only 1 foot below grade the basement finished space is not added to the square footage of the building. While the footage is NOT added, there is value added for finished space below grade. In reality basements are often dark, musty, moldy, damp and water prone, which makes them less desirable to the buying public. imho, be cautious on how much you spend, because your return on investment of below grade space may be less than you expect.
- Member since 2024 · 222 posts · 161 votes1y
It can work and I personally have done it. Like any investment it's important to determine if it pencils, the market potential, legality in your area, and consider your long term goals for a property. You have a number of things to consider in your due diligence.
What makes financial sense to you may be different than anyone else. You alone know the sandbox you play in. If it's outside that box you really must determine if you really want to expand your box or leave it alone.
Well, a law just passed here inMA making them completely legal. Also my basement is a walkout so it is partially out of ground. I don't think it would be super costly. It's just. Does having e legal rentable space make the home more valuable than simply just finishing it?
- 1yTheresa HarrisPro MemberMember since 2019 · 15k+ posts · 11k+ votes
Find out what you need to do to make a legal suite. In areas where the cost of living is higher, the suites can be a good selling point (often called a mortgage helper). Make sure whatever you do, if the next owner doesn't want it as a separate suite, it can easily be converted back.
- 1yLien VuongBusiness MemberReal Estate Agent · Boston, MA · Member since 2018 · 2k+ posts · 1k+ votes
ADU designation definitely makes it more valuable as you're able to rent it out separately from your home. That's plausible in every zip code today for a single family home and I think it's worthwhile for you to execute.
The Elle Group5152 Reviews - Investor · Medford · Member since 2019 · 12 posts · 7 votes10mo
We built a detached carriage house/studio in our backyard in 2007. Architect did a nice job, 450 sqft, used the loft space as an office and the kids used the main area as an art studio. It served as workshop, furniture restoration, etc. no bathroom, no shower, no kitchen. Electric heat, a minisplit, and a sub-panel. In 2013 we thought, " why not stick a bathroom in there and make it into a place we could Airbnb? So we did. 9 years of very solid rental income. Then, a few years back, a code enforcement official from the town came knocking, someone in the neighborhood 'complained.' We were told to delist from Airbnb, remove the bed. Each day we didnt comply would be a $1k fine. We took the bed out and the place taken down from Airbnb that afternoon! They came back to make sure. Did not have to rip out the bathroom fortunately. Then the state of MA ADU legislation arrived and we thought, great! Back in business. Not so fast. Needs to pass a HERS rating and needs a kitchen and needs to have a hookup for an EV. Did not pass the HERS rating (Home Energy Rating System?). So we use it to hang out and store stuff. Retrofitting to pass HERS would be costly, as would adding a kitchen in a way that makes sense for us. Never regretted doing it, but all posters are correct. Investigate, talk to the local bldg department, do your research. The additional income will be nice if the place is done well and in a desirable location. Good luck.
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