basic design/ advice for purpose built shed needed

Hi, Stumbled across this forum and have spent last few hours looking through but bit confused.. Getting an idea there is quite a bit I dont know! Picked up a few comments on 3 leaf worse than 2. Assuming this is amount of boards? Did I read more mass will not always work on low freq ? Can anyone point me to a basic spec ? Main objective is to play my drums and and have a bass player/sax in as well. I would like the room to double up for mixing as and when but main concern is to keep as quiet as possible for my neighbours. I live in middle of hove (brighton) In brief I have an overall floor plan of 5.2 mtrs x 3.2 mtrs to play with. I am approx 7 mtrs from neighbours houses. I will be building a shed from scratch (concrete base starting tom) in the bottom corner of my garden. The shed will be flanked on two sides with brick garden walls. These are the boundary walls so i will not actually be using them but perhaps they will help? I would like a window for day light . I have two double glazed units approx 2.6 x 0.5mtrs long 20 mm thick. I was going to go for brick outside skin then a plasterboard inner skin. Using the isolation metal strip thingys 1. Do I need to float the floor? Or is it waste of time as Im in my garden!!?? 2. I was going to go for brick outside skin. Correct? 3. I looked at using fire bricks for outer wall as they were the heaviest (densest) I could find or is there something else better ? 3. Roof sloped 2.5 mtr to 2.1. Should I follow that on the inside skin, as it seems your supposed to keep surfaces non parallel ? Sorry if this is a bit unexciting for you guys as I know your into the finer details ...

Going to reply to my own post ! I have just found this viewtopic.php?f=1&t=18270 so have this info now. Looks like I need to look at "room size ratio" and think ive saved some money regarding decoupling... if there is anything else any one can add about my original post then thank you in advance.

Hi "drumcato", and welcome! :)

Sorry if this is a bit unexciting for you guys as I know your into the finer details ...

Not at all! Big picture or fine details is all the same here! And this whole acoustics thing certainly can seem overwhelming the first time you take a close look.

Getting an idea there is quite a bit I dont know!

I've been studying this stuff for years, and I get the same feeling, so don't feel alone there! In fact, the more I learn, the more I realize that there's even more I don't know.... :)

Picked up a few comments on 3 leaf worse than 2. Assuming this is amount of boards?

Not really. I mean, yes, 3 leaf is worse than 2, without any doubt, but no, it's not about the number of boards: it is about the number of leaves. In acoustics, "leaf" is just a large, massive, rigid surface that presents a boundary to sound, with air next to it. A leaf might be made up of several thicknesses of boards, of the same or different type, but in direct contact with each other. For example, the inner-leaf of a room might consist of a layer of plywood, followed by a layer of drywall (plasterboard). So a "two-leaf wall" is one where there is an outer leaf (for example, the outer wall of your upcoming studio building), then an air gap, then an inner-leaf (the wall of the rehearsal room itself). In a typical house wall, the two "leaves" are both attached to the same stud frame, but in a studio wall, the leaves are "decoupled" from each other, meaning that there is something that prevents vibration on one leaf from being transmitted directly to the other leaf by direct mechanical connection. That "something" might be air, or it might be some type of resilient mounting (isolation mount). The term "leaf" also applies to ceilings and floors, not just walls.

Did I read more mass will not always work on low freq ?

Yes, no, maybe.... ! :) :shock: :? Not very helpful, I know. Put it this way: it's not so much the mass itself, as how you distribute the mass. The absolute best way of stopping sound is to simply put a barrier in front of it that is so massive (heavy) that the sound waves cannot make it vibrate. Sounds good on paper, but in practice you need an enormous amount of mass to do that, if you have it all on just one single leaf. If you do that, you are subjective to a law of physics know as "mass law", which is not very heartening. On the other hand, if you take a much smaller amount of mass and split it across two leaves separate by a spring, then you are no longer subject to mass law: you now have a resonant system, which is an entirely different beast: You can get much more isolation in certain frequencies with a "two-leaf system", at the expense of much less isolation in other frequencies (no free lunch!), but if you tune your frequency range carefully, it can cover all of the parts of the spectrum that need it, and leave the rest "uncovered", so to speak. That's the secret of a two-leaf system: It is a tuned system, that resonates at certain frequencies and resists resonating at all others. Tune it wisely, and you can use much less mass than you would need with a single leaf "mass-law" wall. So logically you'd think that if two-leaf is good, then three-leaf must be better, and four-leaf must be outta sight! Not true. Well, true, but not usefully so. While it is true that a 3-leaf wall offers even better isolation than a two-leaf, it only does so for a smaller part of the spectrum, at higher frequencies, and tuning it to cover the the audible spectrum is a lot harder: once again, you need more mass, and more space, to get the same effect as you could have got with a 2-leaf. So the basic rule is; two-leaf, only two-leaf, and nothing but two-leaf. Occasionally it is impossible to avoid a 3-leaf system, for reasons beyond simple acoustics, and there are methods of dealing with that, but with certain limitations.

Can anyone point me to a basic spec ?

I could, but you'd probably be prim material for the mad house within about ten minutes! :) Are you SURE you want it?... ?

Main objective is to play my drums and and have a bass player/sax in as well. I would like the room to double up for mixing as and when but main concern is to keep as quiet as possible for my neighbours.

Drums are the hardest of all instruments to isolate, for two reasons: 1) They are the loudest of all, easily hitting 115 dB, and more. 2) They put put a large amount of that energy in the low end of the spectrum, which is the hardest to isolate anyway. It's actually not hard to isolate 115 dB if it is all above 10 kHz. Piece of cake. But isolating 115 dB when it is all below 1kHz is a very, very different game. Next to impossible. Fortunately, drums do spread it around the spectrum a bit, but is is still notoriously hard to isolate drums. It would be good if you could put real numbers to your goals here: define exactly how many decibels of isolation you need. That's the key to getting this right. You can't take "not loud enough to annoy neighbors" and plug that into the equations! You need a real-world number.

I will be building a shed from scratch (concrete base

Excellent! A clean build from the ground up is your best bet here, since you can do everything right form the start, and are not subject to limitations of existing structures. And yes, a concrete slab-on-grade is your absolute best friend, the ideal place to start, if you want high levels of isolation.

The shed will be flanked on two sides with brick garden walls. These are the boundary walls so i will not actually be using them but perhaps they will help?

They might... or might not. If they happen to act as third leaves, .... ! :)

I would like a window for day light .

That makes things a lot harder. It is fairly easy to construct a room that will get you 80 dB of isolation, but as soon as you have to put a door in it, your job got much harder. And if you have to put a window in as well, it got harder again. Those are "discontinuities" in the leaves, and reduce isolation. Doors are worse, as they have to open and close, but widows are pretty bad too.

I have two double glazed units approx 2.6 x 0.5mtrs long 20 mm thick.

sorry, but those are no good. Sell them, put the money in the bank for a while, until you have the design in place, then use that to buy the type of glass you will need. Think about this: each of those windows is a two-leaf system. Put them together and you have a 4-leaf system :shock: :!: Double-glazing is OK for typical house noise and even some types of road noise, but totally useless for studios. The glass is way too thin, and the leaves are way to close to be of any use for low frequency isolation.

I was going to go for brick outside skin then a plasterboard inner skin. Using the isolation metal strip thingys

Brick outer-leaf is great: lots of mass. Plasterboard inner leaf is also great: if done right. But you don't need the "isolation metal strip thingys" (more commonly called "resilient channel" :) ) if you build your inner leaf properly, on a decoupled frame. Resilient channel (a.k.a. "RC") is meant for a different purpose, and you don't need it.

1. Do I need to float the floor? Or is it waste of time as Im in my garden!!??

Probably not. This should answer your question: viewtopic.php?f=2&t=8173 Very few studios need a floating floor, and doing it right is complicated and expensive. Ignore the garbage you see on YouTube about guys "floating" their floors with 2x4s on bits of rubber.... :lol:

2. I was going to go for brick outside skin. Correct?

Yes, but seal it well! After mass, the next most important thing you need for isolation, is air-tight seals everywhere. Both leaves must be hermetically sealed. Brick is porous.... So is mortar. So the inside surface of that leaf must be sealed totally airtight. Here's a thread of a studio build that is currently in progress (very close to completion), of a guy who did something very similar to what you are planning: viewtopic.php?f=10&t=17575 Well worth the read!

3. I looked at using fire bricks for outer wall as they were the heaviest (densest) I could find or is there something else better ?

There is some difference: common red brick runs about 2000 kg/m3, fire brick is around 2400, and "chrome brick" (no idea what that is!) is about 2800. But any of those will do. That's good density, no matter which way you look at it.

3. Roof sloped 2.5 mtr to 2.1. Should I follow that on the inside skin, as it seems your supposed to keep surfaces non parallel ?

Non-parallel is a myth. Partly. Sometimes. Once again, not a very useful answer! Like floated floors, "non-parallel" is a buzz word bandied around by folks who often don't have a clue what they are talking about, and assume that it must always be necessary because they saw it in photos or a book some place... There are reasons why you might not want parallel walls in a room, such as an RFZ design in a control room, for example, or to eliminate flutter echo. But there are other ways of eliminating flutter echo. Non-parallel can be good, but is not a "written in stone" rule about studios. You can do a normal rectangular room quite successfully, if you want, or you can splay your walls and angle your ceiling if you want, also quite successfully. The key is in how the room is designed, and how it is treated. It is a useful tool in the designer's tool box, provided that it is used for a good acoustical reason, and done correctly. So that's my long, convoluted way of saying "No, you don't need to angle your ceiling, unless there is a specific design concept that you plan to use, and that requires it".

Looks like I need to look at "room size ratio"

Room ratios are important too. But you don't need to go nuts over them! Just get away from the bad ones, get close to one of the good ones, and call it a day. - Stuart -

THANK YOU THANK YOU THANK YOU :D :D Thanks for taking the time for a detailed reply .. First time on a forum , I must remember to return some expertise to the net if I get the chance ! apologies for shouting below i am trying to make sure you can see my reply to your reply. hope that makes sense :) Quote: Can anyone point me to a basic spec ? I could, but you'd probably be prim material for the mad house within about ten minutes! Are you SURE you want it?... ? YES PLEASE! Quote: Main objective is to play my drums and and have a bass player/sax in as well. I would like the room to double up for mixing as and when but main concern is to keep as quiet as possible for my neighbours. Drums are the hardest of all instruments to isolate, for two reasons: 1) They are the loudest of all, easily hitting 115 dB, and more. 2) They put put a large amount of that energy in the low end of the spectrum, which is the hardest to isolate anyway. It's actually not hard to isolate 115 dB if it is all above 10 kHz. Piece of cake. But isolating 115 dB when it is all below 1kHz is a very, very different game. Next to impossible. Fortunately, drums do spread it around the spectrum a bit, but is is still notoriously hard to isolate drums. It would be good if you could put real numbers to your goals here: define exactly how many decibels of isolation you need. That's the key to getting this right. You can't take "not loud enough to annoy neighbors" and plug that into the equations! You need a real-world number. CAN I SAY BETWEEN 100 - 115DB REDUCTION ?? say £5000 uk pounds budget Quote: The shed will be flanked on two sides with brick garden walls. These are the boundary walls so i will not actually be using them but perhaps they will help? They might... or might not. If they happen to act as third leaves, .... ! THE BRICK GARDEN WALLS ARE 150MM AWAY FROM THE OUTER NEW BUILD SHED WALLS AND 3000MM SHORTER IN HEIGHT ill post up a basic sketch up plan when i get the time but if you get time let us know your thoughts. [quote]Quote: I would like a window for day light That makes things a lot harder. It is fairly easy to construct a room that will get you 80 dB of isolation, but as soon as you have to put a door in it, your job got much harder. And if you have to put a window in as well, it got harder again. Those are "discontinuities" in the leaves, and reduce isolation. Doors are worse, as they have to open and close, but widows are pretty bad too. A BASIC SPEC COULD BE HANDY HERE AS I NEED TO BUILD THE DOORS /WINDOWS (OR AT LEAST HAVE OPENINGS IN THE BRICK WORK AND KNOW WHAT SIZE TO HAVE THEM) [quote] I have two double glazed units approx 2.6 x 0.5mtrs long 20 mm thick. sorry, but those are no good. Sell them, put the money in the bank for a while, until you have the design in place, then use that to buy the type of glass you will need. Think about this: each of those windows is a two-leaf system. Put them together and you have a 4-leaf system Double-glazing is OK for typical house noise and even some types of road noise, but totally useless for studios. The glass is way too thin, and the leaves are way to close to be of any use for low frequency isolation. OK FAIR ENOUGH !! :wink: Quote: I was going to go for brick outside skin then a plasterboard inner skin. Using the isolation metal strip thingys Brick outer-leaf is great: lots of mass. Plasterboard inner leaf is also great: if done right. But you don't need the "isolation metal strip thingys" (more commonly called "resilient channel" ) if you build your inner leaf properly, on a decoupled frame. Resilient channel (a.k.a. "RC") is meant for a different purpose, and you don't need it. COOL OK BETTER TO GO FOR INNER LEAF "PROPERLY MADE" ASSUMING THATS TWO BOARDS WITH GREEN GLUE WITH WELL SEALED EDGES. 3/4 /5 BOARDS BETTER FOR ACHIEVING THE HIGHER ISOLATION FOR DRUMS?? :shot: 3. Roof sloped 2.5 mtr to 2.1. Should I follow that on the inside skin, as it seems your supposed to keep surfaces non parallel ? Non-parallel is a myth. Partly. Sometimes. Once again, not a very useful answer! Like floated floors, "non-parallel" is a buzz word bandied around by folks who often don't have a clue what they are talking about, and assume that it must always be necessary because they saw it in photos or a book some place... There are reasons why you might not want parallel walls in a room, such as an RFZ design in a control room, for example, or to eliminate flutter echo. But there are other ways of eliminating flutter echo. Non-parallel can be good, but is not a "written in stone" rule about studios. You can do a normal rectangular room quite successfully, if you want, or you can splay your walls and angle your ceiling if you want, also quite successfully. The key is in how the room is designed, and how it is treated. It is a useful tool in the designer's tool box, provided that it is used for a good acoustical reason, and done correctly. So that's my long, convoluted way of saying "No, you don't need to angle your ceiling, unless there is a specific design concept that you plan to use, and that requires it". I WOULD LIKE IT SLOPED AS PREFER LOOK BUT WHATEVER WORKS BEST! LASTLY ON THIS ROOF POINT, I COULD PUT A LOAD OF SOIL ON TOP AS WELL TO INCREASE MASS ( A SEEDUM ECO FRIENDLY STYLE THING) I suppose my next thought is how the roof will be constructed ? I read the post you sent me to on your last reply http://www.johnlsayers.com/phpBB2/viewt ... 10&t=17575 where it goes into 3 leaf because of his tin roof... I can have a grass roof (seedum etc) so in a sense a roof of two plywood sheets with a dpc on top and then soil or concrete tiles ??? The inner leaf will have walls and ceiling made up of 2 boards green glued together and attached to 4x2 timber studs. An air gap of say 100 mm? Where would the insulation go or specifically which leaf to attach to? Thanks again....bed calling ! (Ive notified myself about replys now, so sorry if i seemed rude in not saying thanks before) cheers Andy

Hi again, Couple more thoughts 1. Regards window - I could make a heavy shutter to put over window, particularly in the evening when neighbors are home and dark most of the time anyway ... 2. Would it be worth building the second door ( into the second leaf) into the actual room a little? in a sense creating a larger air gap between the two doors when closed. Like a small porchway. 3. I could use bricks instead of plaster board for the second leaf if it would help the low frequencies as I think Im most paranoid about the bass guitar notes ,bass drum etc swamping the garden/getting through to neighbors. Although to be fair the amount of time its sunny in the uk most of my neighbors will be inside ! I want a fairly flat sound with a little life for my bands to play off but def not too lively as playing/rehearsing in a live situation things can sound good to quickly ( in my opinion) Thanks

Hi again heres my spec on two jpegs ... i really need some air intake/conditioning (what do you guys do and how !!??) I can change anything to some degree .. please let me know if I am going in the right direction. The height of roof is going to be 2.5 mtrs high on the long side of the shed (next to garden wall ) going down to 2.1 mtr on the window wall... Is air gap ok ? can i get away with smaller bearing in mind my optimistic isolation objective... 110 db!!! (or as close as poss) Should i put more board on inside of my new brick wall? I will have a band in there a lot so drums,sax,guitar ,vocal, double bass amplified.

I replied to this in your other thread, here, I think: viewtopic.php?f=1&t=18421 Let me know if there's something I didn't cover there. That's why it is better to keep all your posts together in one thread. :) - Stuart -