Ironwood Builders, thank you. The flat roof actually created the problem that we have to remedy...that is, inside leak. Unfortunately I was on my own when the house was designed and built so I wasn't as involved as should have been. My husband was a builder in his previous life so I lucked out on that count! Want to keep cost down but have somethong that will blend with house style. Talked with 4Seasons Sunrooms but they cost equal to stick built of same footprint. Hence, my thought that a 'vestibule' would suffice. I.e. approx 6 x 8 space. Will have to talk to architect. Thx again for your insight!

I actually like the lines of the house, unless you're dead set on changing the look completely, I would just redo the flat portion properly to resolve the leak. I suspect that the problem lies in the roofing materials and installation.........the problem with most residential roofers is they try to use residential products on roof like this that weren't designed or intended for an extreme low pitch and that's what you've got from the appearance of the picture. The key is the product itself, the installation and the flashing tie into to the metal roof.........I would suggest an SBS Modified Bitumen membrane, something like a Siplast Pardadine 20/30......some pictures of the transition of the flat roof area to the rest of the roof would be helpful........

Appreciate your comment! Builder was concerned from the get-go about all the roof angles coming together and how snow load and freeze-thaw would affect it. A membrane was installed because of the 2-1/2 / 12 pitch. Had some rough winters and was never able to keep snow from building up where flat roof met cupola (right side as you look at photo). Since it needs to be repaired I want to add an entry/vestibule that will soften the transition from house to outdoors. Door faces southwest....cold in winter, hot in summer.....and buggy! Have been trying to come up with an idea that will not break the bank but will also not ruin the look of the house. BTW, have been enjoying reading your comments on some of the other discussions.......home design and construction is not for the faint of heart :)

If you add a new square entry vestibule in front of existing front door, with lower than existing -- say 24" high "side walls" and all carefully framed (broken up into narrow and wide) asymmetrical colored aluminum framed matching glass elements and move entry door out but not include existing window above (drop out top window / use elsewhere in new scheme), you will be able to leave the element of the flat roof that is so important to your architecture now, but get some forward slope onto it where it drops over new front door with shallow hip framed side roofs over a new 8 - 10 ' square front entry vestibule. The roof element will start in exactly the same place, and have no impact on the cupola this way, but it will have a slight forward slope and be built about two feet wider than it is now, so snow that gets underneath will only blow in to the hip roof below, not set in on the sides.

You won't lose much Frank Lloyd Wright style, but gain a mudroom / sunroom space big enough for a pair of chairs and bistro table on one side to enjoy that flowering redbud! I recommend you could use the stone trim on the rest of the house below the glass to help tie it together and differentiate it from existing elements that step back - you might even drop the ceiling in the vestibule to 6" lower than existing ceilings so it feels like you have arrived / have high ceilings when you step into the main house. This would help the new side hip roof on the new solarium come in under existing hips but above existing window line . . . and then go and take a look at how Susan Susanka uses interior wood trells trim at ceiling height to make interior transitions - the not so big house book - you might like the result better after all inside too as you gain back your entry area space in the main room.

Gorgeous house - love the flat roof element, but even Frank's homes had practical problems!

That is a crazy cool house and it would be a shame to change it's character. I have a thought that might work I'm pretty sure it would look good. Do a curved/arched roof over that section. It would not interfere with the cupola. I would have a drawing done before you do anything though.

It is a very nice house. And it's too bad the flat roof made it's way into the final design. So you can attempt to address the situation or you can follow Frank Gehry's maxim that, "All great architecture leaks."

Easiest fix that I can see right now is to extend the cupola shape across to create the new vestibule that you are looking for. Make it the same width as the flat roof - so that there is a step in the wall at the cupola - and then draw that shape straight out. This makes for an incredible 1.5 storey entry that could have as much glass as you like in it. It also would compensate for any loss of light that might come from losing the two cupola windows. Although I doubt that they are significant.

Have a look at the attached. It's a basic model, but illustrates the point. I left the shape of the flat roof on the new right side wall so you can visualize things a bit better.

And here is another with a lower entry that is then stepped up at the existing wall plane.

Curved roof...

and the last one.