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Advice before construction please.

Discussion in 'Home Cinema Building DIY' started by tykent, Apr 26, 2004.

  1. tykent

    tykent
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    Hello all.

    I am just about to start work on converting my detached garage to a dedicated Home Cinema room but thought I'd get some advice from all of you who have already started/completed the projects. ;)

    Here is the picture as the garage stands from outside.

    [​IMG]

    and currently the mess that is inside. (Bookcases aka DVD storage )
    [​IMG]

    My initial questions are should I really look at removing the roof and making it flatter. I was thinking it might suit the acoustices better sloped and the projector will be lower the further I move it back. I was kind of planing to stud, fill with rock wool and plaster board the walls. I was hoping to insulate the 8" roof joists and plaster board that too.

    Dimensions of the garage are: 6m long by 3m wide. Height 2.7 sloping to 2m.

    Currently I am looking at bricking up inside the Garage door and having a fixed screen of about 80" diag with a projector (prob the Sanyo Z2 subject to a demo). As you can see from my sig I have a number of speakers but still no AMP yet.

    Any advice at this early stage would be appreciated.
     
  2. fufna

    fufna
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    First of all you need to put a proper roof on it, I'd be inclined to try and keep the sloping aspect and step the floor so you can have tiered seating;)
     
  3. tykent

    tykent
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    I am awaiting a quote from a local builder to replace the roof. The current roof is watertight but it is corrogated asbestos sheeting. I did consider just running a few extra joints under the sheeting then filling the void under the roof with insulation material and screwing plaster board to the joists.

    I'm afriad the quote will be my projector and amp budget :(
     
  4. Nimby

    Nimby
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    Hi tykent

    If the roof isn't leaking then leave it in place. Probably over half the roofs here in in Denmark are corrugated asbestos/cement. They have a life of about 40-50 years before they get "woolly" and moss covered on the top surface. They still go on working well even if they aren't "pretty" any more. There's really no point in changing to a felted flat roof if that's what you had in mind.

    Keep your present sloping roof/new ceiling if you can. It will help to spread the bass troughs and peaks from the floor/ceiling surfaces and improve the sound quality.

    If you MUST change the roof covering I'd suggest you browse for <Onduline>. I've just built a similar sized workshop to your garage/HT room using Onduline for the roof. It will work down to low angles and is very light. It doesn't make a horrible row like steel sheeting when it rains either.

    When you start insulating the walls and ceiling remember a polythene DPM (Damp proof membrane) just under the plasterboard or plywood.

    The only slight worry about the project is the 2:1 ratio of length to width of your proposed HT room. It <might> pay to reduce the length slightly internally to achieve a better ratio that avoids obvious overlaps between eigentones. Which might cause bass boom.

    Nimby
     
  5. CoZMoSiS

    CoZMoSiS
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    That looks like a great project, i'm jealous ! Certainly i agree with the roof issue, leave the slope it'll help eliminate and lower frequency standing waves. Nimby makes a good point about the 2:1 ratio however, im thinking if its impractical to reduce the dimension then certainly consider some kind acoustic diffusion or absorption technique. http://www.auralex.com/ have some great products for this, tho i fear they are not the cheapest (ie: quite expensive).

    The most effective 'minimal' thing to do is to work out the seating and speaker placement, then get someone to move a mirror (whilst you are sitting in the viewing position) and put some absorption material for example in the place where you can see the speaker in the mirror on the wall. I'd personally be inclined to consider some kind of bass trap at the rear of the room if indeed it ended up a bit boomy.

    Bear in mind, im not suggesting what you should do, just trying to open your mind to options you may not have considered :)
     
  6. tykent

    tykent
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    This conversion business seems to get more and more complicated the more you get into it. I read somewhere else on this forum that you should not just lay a new floor on the existing concrete garage floor as moisture rises up through it and expels through the unsealed garage.

    As I will be effectively sealing the walls and ceiling I was wondering if I need to lay 3x2 across the floor and then lay floor board on top. This would allow me to replace some of the bricks under the newly raised floor with air bricks allowing moisture to escape. I could add a vapour barrier between the 3x2 and the floorboards.

    Just wondering what effect having a hollow floor as I could not fill it with insulation because of the air flow might make to the speakers, sub on it.

    Any advice please ?
     
  7. fufna

    fufna
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    You do indeed need to have air circulation between the two, as in almost all modern (past 120 years or so) house construction.

    Aside from blocking ventilation, anything you pack into the space between the two surfaces would act as a "wicking" agent to draw moisture into you lovely new floor!

    A good solution to stop boom is use heavy mass materials in the first place, ie build a heavy joisted floor.

    This is actually very easy, the only part that takes any real time is getting everything level and securely bedded to the walls.

    remember wood expands and contracts, so leave room for it to do so.
     
  8. fufna

    fufna
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    Another thing I forgot to mention is get your power sorted VERY early... try and get a dedicated spur from your unit out to a seperate consumer unit in the HC room, it's so worth the effort in the long run... and you can laugh at the sheep spending 80 odd quid on power cables when you have a cleaner supply in the first place:devil:

    Is there really no option of keeping the existing concrete floor?
    I made a point of laying a damp coursed concrete floor in my exterior cinema and have never regretted the effort.
     
  9. tykent

    tykent
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    Thanks for the replies fufna.

    I have already run a dedicated 10mm2 cable out to the garage from the consumer unit for a 32A ring main and 6A lighting circuit. The power currently just runs off a spur from the house.

    I will look into getting the concrete floor damp-proofed as you suggested. Not too sure on the processes myself but have a builder friend I can ask.

    I'm sure it will all be worth the effort in the end.
     
  10. fufna

    fufna
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    A concrete floor is a great base to start from if you can save it.

    A damp course is not too expensive if you do all of the prep work and making good yourself.

    It seems like you dont have any plaster work inside your building so a membrane wil probably not be required.

    with regards to the exterior power to the building, make sure it's armoured cable buried around 2 feet deep with warning tape at half depth. If these prerequisites are not met, the buildings inspector will cut your balls off!
     
  11. Nimby

    Nimby
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    fufna

    Just for clarity:

    Does the open trench with armoured cable in place have to be seen by the buildings inspector to get official approval?

    Nimby
     
  12. fufna

    fufna
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    I don't think so, but they have the right to ask to see it.

    You can also embed it in concrete if I remember rightly
     

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