John Sayers' Recording Studio Design Forum

Hi again, Lucie. There's a rule here on the forum: "No pics means it didn't happen"! So post the pics already! I'm dying to see how it's going in there.

On the floor issue: the problem isn't so much how to finish the surface of the floor, but what to do about that empty space underneath. That's a resonant cavity, to some extent, and the floor is a "drum head" (if you think about it, it's just like a membrane stretched tight over a drum, except on larger scale.) It isn't going to isolate well like that, and adding more mass to it is not an option, since it is just a single leaf, governed by "mass law", which is not very useful.

The problem is that it will vibrate in sympathy with whatever is going on inside the room, as it isn't "damped" either, and if the inside is vibrating, then so is the outside. If the outside vibrates, well, then it is acting like a very large loudspeaker, transmitting the sound outside, which is what you don't want. The ideal thing would have been to have a concrete floor in there, by building the room directly on a concrete slab, but it's too late for that now, and it might not have been feasible anyway.

That's why Tom mentioned the grout: it's one way to sort of re-create the slab that you don't have. Of course, you would have to put some type of membrane between that and the underside of the floor, to prevent water from wicking up into the wood and rotting it, like you said, and you would also need to mix a waterproofing compound into the grout itself, to help it resist water. It's an interesting option, and should work if your builder can figure out how to do it right.

I'm still mulling it over, but I think one other possibility is to fill that cavity under the floor with mineral wool, then seal up all around the edges somehow, creating some kind of "skirt" from marine grade plywood, fiber-cement board, or something else that can handle a bit of bad weather. The idea is to seal it up both airtight and watertight, with plenty of mass on whatever you use to close the gaps. Mention that to your builder as "plan B", and see what he thinks.

OK, now for the inside floor itself: As that article you link to points out, the existing original floor is going to have air paths through it all over the place, and those need to be sealed. But once again, a simple coat of good paint will do that. Anything designed to seal the surface of wood, and last forever. So seal the existing surface with that, then put down a 2" layer of OC-703, or something equivalent, and a couple of layers of 5/8" OSB, plywood, MDF or something similar on top, screwed to each other (but not to the subfloor!), and leaving a gap all around the edge (5mm or so), such the wood does not touch the walls ANYWHERE. No contact. Fill that gap with some type of very flexible low density expansion joint compound. Stagger the seams (joints) between the two layers of OSB/MDF/plywood (in other words, the joints on the second layers must not line up with the joints on the first layer).

Seal that top surface with the same stuff you used on the original floor, then lay your laminate flooring on top of that, with whatever underlay that manufacturer recommends (provided that there is no air in it!).

Once again, the laminate flooring cannot touch the walls: it rests only on the floor, with a gap all around the edge of the room. Don't fill that gap with anything: leave it open. When you install the skirting board, the same rule applies: attach it to the walls this time, in the normal manner, but leave a small gap underneath it, so that it does not touch the floor. It will hide the edge of the floor, but without touching it. Just put some sort of shim under it while it is being nailed in place, then pull the shim out when it is done, leaving the empty gap where the shim was.

On the other flooring options you were thinking about: adding neoprene pads, framing and a deck is called "floating" your floor, and is rally hard to do right. Plus, it takes up a lot of height, and you don't HAVE any height to spare! The method I described above isn't really floating the floor: it's just decoupling it, to a certain extent. So it won't isolate completely, but combining that with the treatment underneath should be enough to get you a good level of isolation, and it takes up as little space as possible: a bit more than 3-1/2", depending on how thick your laminate is.

Yup! Carpet is NOT a good thing, acoustically, in a small room. It absorbs the wrong frequencies and doesn't touch the ones that do need treating. It makes your room sound worse, not better.

You are going to need something on the ceiling in any case, but it can be arranged thicker around the edges of the room, and not so thick in the center, to give you a bit more headroom where it matters. OR it could just be in the form of a "cloud" directly over the drum kit itself. But you do need plenty of acoustic absorption up there!

Yes. No. The method I described above for your floor basically IS a drum riser, just made big enough to cover the entire floor. So yes you do need one, but you already have one if you do the floor like that! You don't have enough room height to add another one, in any case....

They look fine. Those will work great.

Yup! Floor to ceiling. That's the way.

no, not really. What matters is to get a large front face, hopefully around 30-something inches across, but as long as you can get 20-something inches you should be OK. The angle isn't that important, as that's just a broadband absorber, not tuned, so any angle is good.

Those aren't really bass traps, but rather just absorbers, to treat flutter echo and things like that. You will need those, but don't make them yet! In fact, I'd really, strongly, powerfully, forcefully suggest that you test the room before you put ANY treatment in! As soon as the room itself is done, I would really like to see how it is reacting acoustically, with nothing in it, in order to give you good suggestions on how to treat it.

This sounds really complicated, but is actually very simple. There's a program you can download for free, called "Room EQ Wizard" (or "REW" for short). It does everything for you. You just hook up your computer to a good speaker and microphone, and run the program. It puts out some strange sounds from the speaker, records the result back into the mic, analyses that, and then generates several different and very useful graphs showing the acoustics of the room. It saves a file with all the tests data in it, so if you e-mail me that data I can do the analysis, generate the graphs, and figure out what needs to be done to the room.

Then you can put in the first round of treatment, and test the room again, to see what else needs to be done. Based on that, we'll decide what types of panels, what size, and where to put them. The only thing is that you need to put the speaker and mic back in the exact same place each time you test the room: that is really, really important. So you need to measure where they are carefully, so you can get them back in the identical spot for each measurement.

It's not that hard to do, REW is great, and best of all FREE!

So please think about doing that! It would help a huge amount to get an idea of what is wrong with the room, and how to treat it to make it right.

OK, HVAC:
If you check the specs on the units you are considering, the key number for how much they can cool and heat is "BTU". For that size room, you'll probably need something capable of cooling around 9,000 BTU, but it would be good if you buy it from some place in your area that can figure that out more accurately, given your climate, and give you good advice on the cooling and heating capacity that you need for that size room, with a couple of people in it, and considering that someone will be playing drums, which is quite decent exercise.

There will also be another magic number in the specs: noise. Get the quietest unit that does the job. It's the indoor unit that you are most interested in. That's the one that you want to be as silent as possible.

And don't forget that, in addition to the mini-split itself, you still need ventilation! Mini-split units only cool/heat the air inside the room: they do not bring in fresh air, nor exhaust stale air. You need to install ducts, fans, and silencer boxes (mufflers) to do that.

By the way, the floor is the last thing you need to do: Get all the electrical and HVAC work done first, and only then do the floor. And last of all, the doors and seals.

It's great to see progress! Or rather to "hear" the progress! We can't see it yet, until you post those photos....


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Apologies on the delay in replying only Leigh has been having a rough time of it with his Crohns since I last posted (fingers crossed he's thankfully coming out the other side again now).

Above everything else to do with this build this problem with the floor is what we've been trying to focus our attention on as it seems as if it could potentially wreck the properties of the studio. We've been talking it through with our builder, and through them other builders that they've previously worked with or that they know online, and a structural engineer to try and found out what our best plan of attack might be. At the moment it seems like it's essentially coming down to two options:

1. We remove the majority of the wooden flooring, leaving enough to support the inner leaf, and also remove those joists that we can then get to. We completely seal the joists that we can't reach i.e. those directly under the inner and outer leaves and pour concrete into the now exposed majority of the void (with self-levelling screed). This would leave us with almost the entire void filled but surrounded by a couple of joists on each side. Into these remaining voids we'd introduce rockwool and seal so that it's both air-tight and water-tight as you suggested Stuart. Finally, a low brick wall would be built around the perimeter to help prevent further egress of sound.

2. This is the most radical and would only be undertaken if for some reason step 1. isn't workable! We lift the entire structure using a crane, remove the joists, prep the surface accordingly and lower the complete unit directly back onto the concrete base.

Although the second option sounds expensive, we can hire a crane for £200+strapping however it apparently comes with the most risk: as the internal leaf is entirely disconnected from the outer, if the unit were to twist whilst being lifted it could prove disastrous for the structural integrity of the inner room.

The first option is also potentially susceptible to this problem (albeit on a far lesser scale) when we cut away the flooring however, apparently there's a way of securing the perimeter of wooden floorboards that remain directly to the existing concrete base with a series of huge bolts (that's what we've been told anyway!). Putting these in would hopefully lessen the chances of any flex or movement in either structure while we're working on the flooring.

None of the above is at all fixed in stone though as we're still looking into it but option 1 does seem to be the likeliest contender!

I have to admit I was labouring under the misapprehension that the HVAC system included fans to put in and take out air! In which case we're currently a bit stumped about what type of fans to go for but I'm sure a few hours of Googling will help! Hopefully there's an "off the shelf" fan plus baffle solution I can find that will suit our build.

Stuart, that is incredibly kind of you to offer to calculate what treatment we'd need, thank you so much! Once we get this flooring/void issue sorted we'll definitely be using that software!

And I promise I'll post up some more pics! I'm currently writing this on our iPad rather than on the computer (as it's somewhat late over here in the UK ) so I don't have them to hand but I'd love you guys to see how it now looks with a coat of paint on!

Once again, genuine thanks to you Stuart and to those who have commented on this thread, it really means a lot and it's comforting to know that we're not on our own with this build!

Lucie.

Lucie, I'm not at all convinced that you need to go to such extremes as you mention: Yes, they both are options, but there may well be other, less complicated, less risky options. This whole floor issue is a bit beyond my comfort zone, so I'd really suggest that maybe you should contact one of the real top experts here, such as John himself, or Rod Gervais, or Andre, and ask for their professional advice on what to do. Yes, they'll probably charge you a fee for their services, but I think it would be money well spent. They might tell you that one of the suggestions you have seen here on the forum is good enough, or they might tell you that one of the two suggestions that your contractors came up with is the best bet (cutting the floor / pumping concrete / lifting with a crane), or they might have a totally different perspective, but they are they guys who design and build studios for a living, and have lots of experience dealing with this type of issue. They will know what to do. Unfortunately you went a bit too far a bit too fast, and didn't give us much feedback or chance to check what you were doing, so things have already been done that probably should have waited. The floor really should have been designed properly before you started building the walls, and so should the HVAC. But I also totally understand your need to get this studio done fast, so your haste is understandable. Fortunately, I'm sure there are solutions, and that the final outcome will be good.

Anyway, from my personal point of view, I would point out that your floor only needs to be as good as the rest of the structure, in terms of isolation. Or rather, it only needs to be as good as the weakest link, which I suspect will be your door. At a very rough guess, your walls are probably going to get you isolation in the mid 50's (maybe 60-something, if you got lucky and they did a great job on the build). But you haven't mentioned what your plans are for the the door, and that's the key here. Getting 60 dB of isolation from a door is not easy. Let's say that you go with double (back to back) heavy solid core doors on separate frames with good seals, and together that get you 45 dB of isolation. If that's the case, then it would make no sense to decide on a plan for the floor that gets you 70 dB of isolation! You'd be wasting time, effort and money on that. Rather, just settle for something that gets you a bit better than 45 dB. (Sound is like water: it takes the easiest path out. So if your "easiest path" is the doors, then that's where sound like "leak" out, totally ignoring the great floor and walls.)

Anyway, that's my thoughts (for what they are worth), but I really think you should send one of the top experts a PM, give them a link to this thread, and ask if they could take a look and then offer their professional advice on what to do. The fee they they charge will be worthwhile, and their involvement will save you the stress and heartache of not knowing what to do with the floor. That peace-of-mind alone is probably worth their fee!


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Adding to my post above, I just noticed this comment while re-reading yours:

It shouldn't be entirely disconnected! The sole plates (bottom plates) of the inner-leaf stud walls should have been firmly nailed to the floor. I hope they were not left just "floating". So there should be some structural integrity there. But lifting the whole thing with a crane... Hmmmm....


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.