Garage build - Need solution for large air gap

Hi......first post. Thanks for reading. This is a room in room build. My question is regarding the foundation wall rise (starts lower left in pic). Once the new wall is upright im left with a 4" gap between the existing wall and the new one. Obviously the large air gap is desirable, but how would I fill the space? I would need truckloads of insulation. Thing is isolation is really important on this wall because the next house is max 12' away. Any suggestions? thanks!

Please read the forum RULES (stickies) that can be found at this link: viewforum.php?f=17 Then make certain that this is reviewed: viewtopic.php?f=2&t=3231 Please correct your initial post to conform with these rules and guidelines. Many here will not only NOT help while waiting in respect for owners and other better qualified persons to proceed, but will simply ignore these type of posts completely. You may want to immediately ask "what is it that I have missed". Most often it is as simple as including your geographical location in your profile. It might be that you have not included your budget! Trust me in that the more you know the better others can help you and that the answer to that question is in the forum rules linked page. Until then, good luck,

Sure, no problem. Not underestimating the obvious hard work and expertise within these posts and apologies for being vague, but it's been hard to plan the rest of the build without solving my initial problem. Im confident ill end up spending in excess of $7,000 when all is said and done. For what its worth, I attached my poor excuse for a rendering just so you know where Im at. Needless to say I'll need to develop better SketchUp skills. This is a room I will use primarily for guitar overdubs and mixing. No worries, though......Ill search around the forum a little on this one and post later when I'm more organized. Thanks for the links to the forum guidelines. :)

Once the new wall is upright im left with a 4" gap between the existing wall and the new one. Obviously the large air gap is desirable, but how would I fill the space? I would need truckloads of insulation.

You don't need to fill it completely! Yes, doing so will increase the level of isolation, and not putting in any at all will decrease the isolation drastically, but as long as you have a few inches of isolation in there, you'll get good isolation (provided that you do the entire design and build right, of course! :) ) - Stuart -

I to have that small lip / slip of concrete in my garage build as well. My "lip" is located on the wall that leads to back of the garage facing the neighbors house. I'm doing a two-leaf system room within a room build...so....I knocked out the inner drywall and placing R13 in the existing frame, then building a new frame right next to the end of the "lip" and filling that with R13. I will take pictures of it when I get home after work if it will help you out. Also keep in mind this is my first studio build, while I have been researching this website for months before I decided to correctly build my studio, I hope you can find this information useful.

Idealmind: Thanks! Pictures would be very helpful when convenient. Feels like perhaps I'm overthinking it, but it will be good to see what you've done. Much appreciated.

Just checking in with you man! how are things going??

Hey! I had 2 obstacles to overcome before any framing can be done: 1. relocated hot water heater to exterior of the house (outdoor rated tankless) 2. rerouted my soft water tank to the same location on the exterior of the house. The room is very small, so I needed to free up as much space as possible. Both those jobs are done and Im ready to start framing. Im sure there a few holes to shoot in my design. Open items at this point: 1) Door-layered MDF or solid core pre-fab? the opening is only 2'9" so custom fit may be necessary. I've been reading the door threads which have been very informative. 2) Filling for the 4" air gap between the new wall and existing. (the long wall with the 3" foundation rise)

In a small room you want to maximize the floorspace. In your build, is it a requirement that this wall assembly be constructed as you are posting? Why is the door diagonal to the walls...is that a requirement? You really want to remove that element if it is at all possible...it is that important and I still have no idea what you want to use this room for, but know this for a fact, it is small room and needs an adjustment.

Ok, I forgot the most important element of the existing space which should explain why the lane is required and why I put the door at a 45............ You can see Ive added the existing door that leads from the garage into the house. By placing the studio door at an angle I feel like I am maximizing floorspace as you mentioned, but that doesnt mean I've done that effectively. I only have my instinct to work with. The door at the bottom left leads to a narrow side yard. The neighbors house is no more than 12' away, so needless to say, sufficient isolation is required if my 100W is ever up past 3 (inevitable). Also, on the back wall on the right side is a soffit containing a plumbing manifold, hence the jog in the wall. Worst comes to worst I can tear out the drywall and still access the manifold if I have a problem down the road. Would be fairly invasive, but Im not that worried about it as long as Im not blocking anything with a stud or limiting access in any way. I took the lower photo from the main area of the garage facing the "annex" space where I'll be framing in the room. In the far left corner where the wall drywall is torn out is where the water heater used to sit. Ill be using the room for tracking (close mic and direct) guitars, bass etc. and light mixing. Because of my admittedly pointless floor-plan I've pretty much ruled out desirable acoustics. More or less a gloried practice space with recording facilities (better than nothing, right?). How Im treating the inside of the room after the framing is up?........no plan yet. Yikes. If anything the size of the room makes the project more affordable from a budget standpoint. Ill be spending less for better materials and more amenities vs. building a larger room. Tons of available spots on the electrical panel......adding circuits will be a breeze. But yes, it is a tiny room. It should be cozy, but not too cramped when 2 or 3 people are inside. Thanks for checking this out. Kyle