Frank - I  think of the "no comps" argument requires more research.  Maybe in the neighborhood/just beyond/the market as a whole. Desirability/Appeal come to mind.  Is there someone in your office you can ask for help?  You have provided a lot of information but more is needed.  

Hard to give any specific help without images. Are you saying they have a two story house with contemporary kitchen, the additions are not visibile or wierd floor plan and exterior looks like a house built in the 1980's???  You can't legally call it 1980's - did you check the permits?

Frankly, you need to hook up with an experienced agent from your office.

bed bath sqft and condition CMA is where I wouldd start for a baseline

Comp it against the rest of the homes in the area then make an adjustment for it's main part's age.  If the plumbing and electrical are all new and good, then functional obsolescence is less of an issue.

Is the older part of the home out of date or dilapidated?  Probably not.

Use the comps you have and make adjustments where needed.

I had to take on many such properties here in the rural State of ND. It all depends on how much work you are willing to put into it.

Time to talk to your broker for guidance. 

Without seeing the property and neighborhood it's difficult to answer your question. When I first started I would ask other agents and the office manager for assistance.

Sometimes you have to ask for help. Your managing broker or friendly appraiser is a good start

Could depend on the quailty and design of all the additions and upgrades. I wouldn't worry about what year it was built.

you should have some assistance and guidance from your broker/owner/manager, or who ever is training you.... you would be wise to take some basic training courses through your real estate board or state association of Realtors.... a back to basics course...

I'd look at houses that were about the same size and + or - based on features. The way you said the original building is still attached makes me think it doesn't look like one house? That might make it worth less.

As others have said, someone from your office/area would have to help. There are a lot of factors that are important in doing a CMA (specific location, house style, amount of land, etc) that are location specific.

Good luck!

Frank,

I agree with Michael Jacobs .  Talk to your broker.  A

Carefully make the needed adjustments. The market will determine the actual value.

Despite all the information you provided there is not enough information to provide a meaningful response. 

Get help from someone who understands how to make adjustments to the subject property - much like an appraiser does. 

I can't help you here... don't know enough about the market there, the neighborhoods, no pictures, etc. If you're having a problem get an appraiser.

If you are trying to list the house advise the seller it would be a good idea to just pay for an appraisal.

I don't think I would worry about the year built. Sounds like a discussion with your broker is warranted!

Michael Jacobs has given you some great advice, along with several others. All real estate is local, so go to your broker or call an appraiser to get true market value!

Call 2 or 3 local appraisers.  Ask how they would approach the situation.

Square footage is only one aspect to look for and I would lean toward functional obsolescence as a main detractor of value with a home having this many renovations. It's not so much the age of the home but it's design. Can it compete?

This is actually what you are being paid for. Who needs a realtor if the house was the same as all others sold?

Now, be aware, appraisers are lazy and will fall into the same 'no comps' trap you have fallen into and undervalue the property. Having the house appraised and having completed your real estate agent CMA, you will SEE all the arguments that will be presented by those who what to undervalue your clients house. Now that you can SEE their playbook, it will be easier to justify the true value. Always stay focuses on the tangible assets of this house and never fall into the 'whose comps are better' nonsense.

Your analysis is three fold:
1. Make a true assessment of the tangible assets of the property. This may include deduction for low ceilings and obsolescence if applicable,
2. Adjust baseline (SP/SF) to reflect adjustments. If SF is 15% +/_ of recent solds apply inversion.
3. Embed modified appraisal waiver.

Lastly, the owners time-line will dictate the actual list price. Be prepared, all the other agents will say, 'Too high," "Too low" and those without a clue will chant 'raise the bar.'  The appraisers will also do the same.

The true value of real estate is what a willing buyer and seller agree upon. Your job is to present the promise of transformation to the buyer and they will do whatever is needed.

in the difficult situation you describe, you must PROTECT the seller. Every mistake you allow devalues the product. Do not, Do Not, DO NOT take the house off the market until you negotiate a purchase offer meeting ALL the preconditions. Consider value adding inclusions with the sale of the house that can be easily extracted for negotiation purposes.

If you continue using the real estate agent traditional CMA approach you will simply dig yourself into a deeper hole. And it is from this hole you must pull the other agents who also can not JUSTIFY the value.

That is now your job. Help them justify the value.  This is where tools like CIS Score and JoistApp are indispensable.

If you can't figure this out maybe this is not for you.

What's the condition of the old part of the home?  Does any of the surrounding homes (comps) have additions? When reading your questions, it looks like this is the only home with a section built in 1959 and the rest of surrounding homes (comps) are newer.  I think it's very hard to give an opinion without seeing the house and the surrounding homes in the neighborhood.  Also I'm assuming they had a permit everytime they added an addition.  I would ask my broker or tell the seller that it's better to have the home appraised by an appraiser.  Best of luck!

Do square footage. I can't believe that you think the 'original part of the 1959 house' is confusing. In fact, the seller could have made a monster that will not be easily sold with all these different wings. 

2006 means it needs another renovation.

sf adjust- replacement cost in here $100-150/sf. 

If the interior of existing home is modern there is no adjustment on condition. 

However, it is valid to duduct on age say $30-50K with few lenders question you.

One can also throw in a newer similar size home by extending the distance showing your analysis is accurate. 

I have had very unique properties with little to no comps, and have called an appraiser to do a value appraisal.

It's hard to say without seeing all the properties and depends on the quality of the upgrades and how harmoniously all the additions blend in. You need to seek local advice.

 Good luck, Frank. You have gotten lots of good suggestions here on how to tackle your challenging CMA.

You need the help of your broker or another experienced agent to do this properly.

I would highly recommend you take an appraisal class which will help you understand how to make the adjustments for unique properties that don't fit with the available comps. 

Definitely speak with your broker - I don't know your specific area and what the average adjustments would be, the location of the property and so much more!