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Coupling to existing garage ceiling Vs. Creating triple leaf?
Old 1 week ago
Gear Head
Coupling to existing garage ceiling Vs. Creating triple leaf?

The garage I'm going to be insulating has a large-ish roofspace which is great for storage but complicates the insulation somewhat. I've attached some plans; the garage is internally 7m by 3.7m by 2.44m.

My current plan of room-within-a-room-ing includes a floating floor and insulated walls with an air gap to the existing cavity brick walls of the garage; I'm also planning to put a ceiling on my room-within-a-room in order to get more uniform insulation and fully decouple it from the existing garage structure.

The issues this raises are (1) fiddly arrangement of building a hatch into this roof directly below the existing hatch so that the roofspace storage space is still accessible, (2) losing too much height in the room between new floor & ceiling and (3) concerns about triple(or more)-leafing my ceiling.

On (3), which seems to be the really concerning one, the new ceiling/existing 'drop' ceiling could be like the STC57/63 examples in the leaf example picture if I removed the lower layer of ply attached to the existing beams and added insulation to both on top of the new ceiling and under the existing ceiling (between the beams).

Which would seem fine except that there's obviously a roofspace above that bordered by a roof, meaning another space and another border...which seems like a triple leaf system. Obviously I want to avoid that, but the only other option is not putting a ceiling on my room-within-a-room and instead using the existing 'drop' ceiling as the ceiling for the new room...which means coupling it to the garage. Which seems like the worse option, right?

My budget here is about £2,000 and it's looking like I'm going to blow past it in materials (never mind getting workers in to help with wiring/some of the construction), so I seem to be choosing between these two options.

Appreciate any help/advice and apologies for the probably-too-scattered post earlier in the week; I have several concerns but should probably deal with them one-by-one.
Attached Thumbnails
Coupling to existing garage ceiling Vs. Creating triple leaf?-garage-plan-_2.jpg   Coupling to existing garage ceiling Vs. Creating triple leaf?-garage-plan-studio-_2.jpg   Coupling to existing garage ceiling Vs. Creating triple leaf?-double-leaf-insulation-wall.png  
Old 6 days ago
Lives for gear
By drop ceiling you mean a grid/T bar type drop ceiling with fiberglass tiles? If so I would just take it out...maybe pics would help here.
Old 4 days ago
Gear Head
By drop ceiling you mean a grid/T bar type drop ceiling with fiberglass tiles? If so I would just take it out...maybe pics would help here.
That's my bad Ryan, sorry, I'll take some pictures when I'm round again later today.

I think it's fairly easy to visualise though, in the meantime - the previous owners created a storage/roofspace by laying ply boards on top of the ceiling beams.

They then boxed the beams in by screwing ply boards to the underside of the beams. So when you're inside the garage there just appears to be a flat ply ceiling, with the beams concealed between the two layers on top and below them.

My initial thought was to just lift the top layer, fill the gap with insulation, and then re-fix the top layer. But the more I read old threads and other resources here the more I realised I'd have;

(new ceiling)-->(insulation)-->(air gap)-->(under-beam ply)-->(insulation)-->(over-beam ply)

Which is a triple-leaf system to my (untrained) eye. Then I realised that even if I removed the under-beam ply, there's still the air gap in the roofspace itself and the outer roof of the garage so...

EDIT: slightly unrelated, but I've just had a read through your studio build thread, wow. Way above my pay grade (audio & construction wise) but I hope the build is being finished off(?) nicely. Hope the ankle is healed up as well - a friend of mine had a very similar break when we were hiking over the summer and he's still in a cast. And while most of what you're doing is waaaay above where I'm at (as I said), the point about lighting for studio videos, IG stuff etc. was a really good take-away for me, thanks.

Last edited by Raoul153; 4 days ago at 10:42 AM..
Old 4 days ago
Lives for gear
Ok gotcha-

Are there vents in the actual roof of the garage? In a place with as much moisture as Ireland, I think there probably should be...Either turtle head vents or a ridge vent etc?

Also with the gabled roof, I'm assuming the roof framing is trusses? Is the plywood that is on top of the trusses' bottom chord a complete layer that could be screwed down and made air tight?

It's my understanding that if the roof has vents and the ply sitting on top of chords isn't a continuous sealed mass layer, it won't truly count as a leaf. Here is a post from Rod on this subject-

What is your isolation target?

And thanks! Yeah we're almost done- I'll post another update here soon. And yeah the ankle is healing up pretty well. I still don't have full range of motion back but it's pretty close. I can't wait to actually get in the new space...
Old 1 day ago
Gear Head
Yeah, there's a ridge vent (and the eaves aren't sealed tight against the outside in any case), we are an unfortunately moist peoples on this island.

The framing is trusses, and I could go over the ply 'floor' of the roofspace and screw down anything that isn't fixed down / seal joins up with caulk, aye.

Thanks for that link! Seems the easiest way to do things so I guess I'll go with that.

For an isolation target (which should've been in the OP, doh ), I'm planning to hold rehearsals in here so 50-60dB would be fantastic as I'd hope that would keep the neighbours sweet for evenings. From that link (which roughly agrees with the research I've been doing) you seem to be able to approach 60STC with a brick wall and 16mm plasterboard - if I render the wall and add at least another layer of plasterboard I'd ideally be looking that boosted a little as well.

Looking forward to seeing your finished posts; like I was saying there, reading things that that reminds me that there's levels to this **** - or at least it highlights that idea better than the abstract of Abbey Road or whatever does. Seeing someone posting this huge, involved, basically industrial-level build on a forum where I'm asking for advice on a garage conversion

Should also mention that the late reply is a function of also trying to organise moving into the house this garage belongs to...unfortunately building this studio isn't the only task...

Last edited by Raoul153; 1 day ago at 08:05 PM..
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