Expert: Roger Zona - 10/22/2009

Question
QUESTION: I am considering buying a house and putting an addition on it as an alternative to building one from the ground up. My goal is to create a house that has a comfortable and functional second unit, either to rent out, let family stay in when visiting, or let a potentially needy mother in law live in until her death.

I have several questions. What are the advantages/disadvantages of buying then adding as contrast to just building a two unit building?
How do the permits for each way of doing it differ? If I add, the concrete foundation of the main house will be solid all around. Do I need to open it up to give it access to the addition's foundation? How is old concrete attached to new concrete? Thank you!

ANSWER: Hi Austin,

You pose a common problem - live with the old or create the new.

Regarding the existing - the 1st question is - is the existing house well built?  Does it meet all the latest code conditions?  Is there adequate electrical service available?  Will an additional septic system be required?  Did you have it inspected by a certified home inspector?  Will the addition comply with zoning - are you allowed to create a "duplex"?  Will the investment be justified for future sale?  Will the neighborhood keep its appearance?  (Lots of questions!)

Building a new home allows you to make all your own selections of products from the landscaping to the door knob.  It also allows you to create a floor plan that suits your needs (so you don't have to adapt to an older plan).  A "mother-in-law" suite can be part of the design and also converted to a rental apartment later. (I was an Architect in the past but I still keep up with current trends.)

Frankly I like the idea of a totally new home.  You can select the lot, orient the building to be as "green" as possible, and use newer and better building products.  The building permit process is about the same - plans must be prepared, a survey taken, and, for the addition to the old an inspection to determine if the existing needs to be updated.

As for the foundation question - No the two areas do not need to be open to each other.  The home would be considered a duplex and the only thing common to the entire building is the separating wall - which must be fire rated from the foundation thru the roof.  As for connecting the two, the old foundation must be opened up and the waterproofing removed from where the new walls will attach.  Then the old surface should receive a bonding agent to assure proper adhesion.  I would recommend that reinforcing rod be installed at the connection point.  Using a 24" #5 rod (1/2" in diameter) drill four 5/8" holes at least 8" deep into the old wall at each point.  Epoxy the re-rod into the holes and allow the rods to be cast into the new concrete - at least 16".

I hope this has been helpful.

Roger
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---------- FOLLOW-UP ----------

QUESTION: Mr. Zona - That answer was very helpful. Thank you. As always, a great answer begs more questions. For a duplex built with wood I Joist floors, I assume 5/8 inch drywall on both sides of the separating interior fire wall creates the fire protection, but how does the wood I Joist structure create the fire protection at the I Joist level of the structure? Do the I Joists have to terminate into rim joist(over a concrete wall), then another rim joist snugged to it, then new I Joist extend from the snugged rim Joist? Or In other words, do rim joists create the fire wall in the floor?

One of the reasons I am considering adding to an existing structure is to have a place to live, that is a very short "commute" to the new structure while I am building the new structure. It sounds like there is a chance the existing structure will have to be updated, and updating it will make it unlivable. What do you think? Are there legal issues with living in the old while building the new?


It also sounds like all utilities will have to be updated, including the septic. Is it true the only way to "update" an existing septic is to outright replace it?

Is there a way to estimate the costs of installing brand new electrical service for new construction - new transformer on the ground and all? My phone calls to electric utilities tell me these utilities don't want to directly answer the "how much" question until just before they begin installing it and it is time to pay the bill.

Thank you Mr Zona for your help!

ANSWER: Hello Again Austin:

I fully expected you would have more questions - but that's what I'm here for!  I could be a little more precise if I knew what area you live in.

Your fire proofing assumptions may be correct but you must check with your local building department.  Talk to someone in "plan review" and find out what the codes require.  They vary from place to place.  I live in Florida and every city on the east coast has modified the standard state code.  Not a fun experience but very worthwhile.

The only legal issue you may have to contend with is the total disruption of your life while you live in the construction area.  I've had clients who insisted on staying in their home while I remodeled it but nerves got on edge and tempers flair!!

As for updating a structure - in my area if the improvements exceed 50% of the space and/or value of the home, then the entire home must be updated.  As for a septic tank, often a second system can be added for the new bath and kitchen areas but they must not be too close to a well, if you have one.  Check with you local health dept.  They are the ones that usually issue a septic permit.

New service from the electrical company usually is not a big cost.  The main cost is the new disconnect and distribution panel.  Since the home may be considered a duplex, you can ask for separate service for the addition.  (This applies to a water and gas connection also.)

When adding on to an existing house it is a good idea to have an Architect prepare your plans.  He can save you costs depending on how the new roof line connects, matching design so the house doesn't look like it "grew like topsy" - in other words, good curb appeal may cost a little more but it gets returned with a quicker sale.

Suggestion - for your own peace of mind - make as many product and finish selections as you can before starting construction.  In other words, do a little research.  Too often a customer waits until a builder asks for a decision and then they are rushed and often would have made a different choice.  Start a scrap book.  Make a list of all the things you have to select - especially for color or style.  Then visit your local Lowe's or Home Depot and check prices and make comparisons.  For example:  Front door - single, double, with or without sidelights, with or without glass, size, finish, hardware, threshold, hinges.  Windows - what style (single hung, double hung, horizontal sliding, awning, panoramic), high wind resistance, clear or tinted glass, single glazing or thermo, frame of wood or aluminum or vinyl, color of frame, color of screening, ----  and the list goes on.  Believe me it will make your life much easier.

Good luck

Roger
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---------- FOLLOW-UP ----------

QUESTION: Hi Again Mr. Zona -

Thanks for the wonderful help. I am looking at Colorado Springs. I'm looking at the Pikes Peak Regional Building Department. I'm using the latest version of Softplan. Would I have to buy a new electrical transformer for electrical service? Is there a way to estimate that cost?

Thanks again - Austin

Answer
Hi Again Austin,

You picked a beautiful area - if you can tolerate the winters!!  I can't anymore so I have a summer place in North Carolina as well as a cottage in northern Michigan.  I don't miss the snow and ice at all.

Now to your question.  I'm guessing you need a transformer because your home will be beyond an available power supply.  If you do get a generator large enough to power all your electrical needs - hot water, air conditioning, heat, lights, refrigeration, etc. - you should consider one of the larger gas or propane powered generators.  I have one on my Florida home because of hurricanes but it is not large enough to power everything at once.  I mainly wanted it for cooking and refrigeration during a power outage.  

A full size generator will cost $12,000 to $15,000 plus the cost of a large propane tank.  They are rather expensive to operate considering the price of propane today.  If you are only concerned about a generator to use while building, a gas fired one can be bought for about $600 or you can rent one.  Also, if you have electrical power near by you should find out what the cost is to bring a service line to your property.  Then you can have a "temporary power" pole set by your electrician which will be metered while you build.

Yes, Softplan is a good program.

Good Luck

Roger
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