Double Garage design - East Sussex
Posted: Sun, 2019-Sep-29, 11:57
This is my first post to the Soundman 2020 - Studio Design Forum. Congratulations on building an amazing forum which I know will become an invaluable resource for countless people around the world. Thank you for sharing your time, skill and considerable experience with us Stuart!
My name is John and I’m developing a design to convert a double garage into a music practise room which can also be used to track instruments including drums and electric guitars. The building is in East Sussex, in the South East of England which has a temperate climate, is situated in a residential area, on a hill, amongst woodland and is detached from the house we live in. The garage is at the edge of a levelled area cut into the side of the hill and the South-Eastern aspect of the building is built into the earth to a height of 131cm (4’4”).
It sits on a 4” (10cm) concrete base and the internal dimensions are 4.85m x 4.98m (15’11” x 16’04”) - almost square! There is a half-hipped roof which is 4.46m (14’7”) at the highest internal point. The walls consist of a single tier of brick and are buttressed on 3 sides with breeze block columns (or piers), roughly at the centre point of each wall. There is a structural beam which runs from from the North-West wall to the South-East wall at a height of 2.24 M (7’4”). The North-West wall has an outward opening door and window and the South-West aspect has two large openings for the garage doors.
Although I have learned a great deal of very useful information from Rod Gervais and F. Alton Everest’s excellent books (as well as Soundman 2020) I have a great deal more to learn and I’m fully prepared to do this. Here is a brief outline of what I think I know about achieving my aim - I would be very grateful for any comments, criticism or suggestions if any of you have the (precious) time and inclination.
I have measured the ambient sound level in the area surrounding the garage at 35dB on a windless day and up to 68dB when to wind shakes nearby trees. Passing traffic sometimes elevates the level to 70dB and the occasional light aircraft passing nearby will give a reading of 55dB.
Typically, the loudest instruments I am going to record are drums (I tend to DI bass when recording) which I have measured peaking at up to 116 dB. Local noise regulations are non-specific when it comes to defining an actual level at which sound becomes a nuisance, but as we have neighbours at both sides (6m and 12 metres) I am aiming for a sound transmission reduction of 55dB or greater and while this is ambitious, transmission loss calculations suggests that it’s possible, so I’m optimistic that it can be achieved. I have a budget of £15,000 - £18,000 and intend to undertake as much of the work as I practically can (although I will not attempt any electrical work, fitting the HVAC system or acoustic windows or doors - I would rather pay experienced professionals to do those parts of the job).
I plan to build a single room within a room consisting of two leaves (where possible). The outer leaf will consist of the existing single tier, solid brick wall which will be sealed, up to a height of 221cm, then a combination of 18mm OSB and 12.5mm cement fibre board to meet a ceiling of similar construction, supported by the existing and some additional ceiling chords.
I commissioned a report from a structural engineer who advises that with the correct reinforcement to the chords and lowest beam, this is both possible and safe. This can be achieved by forming a ‘flitch beam' (i.e. adding a 10mm steel plate with two staggered rows of bolt holes, sandwiched between another identical beam and held together with M12 bolts).
The existing ceiling chords will be bolted to the joists with M12 bolts.
The South-West aspect of the building has two large “up and over” garage doors which will need immobilising, sealing and damping.Then the gaps will be framed with timber, insulated with rock wool and an inner wall of one layer of 12.5mm cement board and one layer of 18mm OSB with green ‘glue’ in between.
The inner leaf structure will be a conventional stud frame clad with one layer of 18mm OSB and one layer of 12.5mm cement fibre board with green ’glue’ in between to form the inner wall, anchored to the concrete floor with an air gap of at least 30 centimetres between the leaves, which will be loosely filled with rock wool.
The frame will need to be reinforced on either side of the main beam with two steel 152x89x16mm universal beams in order to support the inner ceiling in a single span. These will need to be pre-drilled in order to attach the connecting timbers.
The inner leaf ceiling will be built using an ‘inside - out” design. The ‘backbone’ will support timber framed modules which will be capped with one layer of 12.5mm cement board and one layer of 18mm OSB with green ‘glue’ in between.
The existing window will be replaced on the outer leaf with a fixed one, glazed with 21mm laminated glass and one on the inner leaf using 12mm glass, conforming as closely as possible to the design in chapter 5 of the second edition of Rod Gervais’s book. The existing door will be removed and two, triple sealed doors (similar to Rod’s “super door”) will be installed with closers.
I have spent a lot of time considering the ventilation requirements of the space and my calculations suggest that the the supply ventilation path should consist of a 200mm x 200mm outer louvre fixed to a plenum box and then approximately 75cm of 6”diameter round duct which will be connected (via a 6” sleeve) to an outer leaf silencer box made of 25mm MDF, lined with 25mm of duct liner, with a cross sectional area of 100 in² (645.16 cm²) throughout and incorporating 8 x 90 degree turns. This will penetrate the outer leaf and feed into another run of 6” round duct (approx 100cm) which will connect to a larger, inner leaf silencer, similar in design to the outer leaf silencer, but increased in size to allow a CSA of 144 in² (929 cm²). This will penetrate the inner leaf at head height, adjacent to the mini-split inner unit, via a deflection grill.
The exhaust ventilation path will be similar only in reverse, with the important difference that it will include an inline fan sized to provide the correct airflow pressure and velocity and powerful enough to cope with the static pressure in the ducts and silencers.
I know that the limited space will make acoustic treatment more difficult - I intend to put bass traps in the two windowless corners and attempt to create a variable acoustic using dual purpose absorber / reflectors which can be moved along wall mounted rails or used as free-standing units on the floor, depending on the desired environment.
I’m sure there is much I have overlooked in this and other areas, any thoughts on how to improve my design will be gratefully received and valued.
Thank you for reading this post and best wishes. John.
My name is John and I’m developing a design to convert a double garage into a music practise room which can also be used to track instruments including drums and electric guitars. The building is in East Sussex, in the South East of England which has a temperate climate, is situated in a residential area, on a hill, amongst woodland and is detached from the house we live in. The garage is at the edge of a levelled area cut into the side of the hill and the South-Eastern aspect of the building is built into the earth to a height of 131cm (4’4”).
It sits on a 4” (10cm) concrete base and the internal dimensions are 4.85m x 4.98m (15’11” x 16’04”) - almost square! There is a half-hipped roof which is 4.46m (14’7”) at the highest internal point. The walls consist of a single tier of brick and are buttressed on 3 sides with breeze block columns (or piers), roughly at the centre point of each wall. There is a structural beam which runs from from the North-West wall to the South-East wall at a height of 2.24 M (7’4”). The North-West wall has an outward opening door and window and the South-West aspect has two large openings for the garage doors.
Although I have learned a great deal of very useful information from Rod Gervais and F. Alton Everest’s excellent books (as well as Soundman 2020) I have a great deal more to learn and I’m fully prepared to do this. Here is a brief outline of what I think I know about achieving my aim - I would be very grateful for any comments, criticism or suggestions if any of you have the (precious) time and inclination.
I have measured the ambient sound level in the area surrounding the garage at 35dB on a windless day and up to 68dB when to wind shakes nearby trees. Passing traffic sometimes elevates the level to 70dB and the occasional light aircraft passing nearby will give a reading of 55dB.
Typically, the loudest instruments I am going to record are drums (I tend to DI bass when recording) which I have measured peaking at up to 116 dB. Local noise regulations are non-specific when it comes to defining an actual level at which sound becomes a nuisance, but as we have neighbours at both sides (6m and 12 metres) I am aiming for a sound transmission reduction of 55dB or greater and while this is ambitious, transmission loss calculations suggests that it’s possible, so I’m optimistic that it can be achieved. I have a budget of £15,000 - £18,000 and intend to undertake as much of the work as I practically can (although I will not attempt any electrical work, fitting the HVAC system or acoustic windows or doors - I would rather pay experienced professionals to do those parts of the job).
I plan to build a single room within a room consisting of two leaves (where possible). The outer leaf will consist of the existing single tier, solid brick wall which will be sealed, up to a height of 221cm, then a combination of 18mm OSB and 12.5mm cement fibre board to meet a ceiling of similar construction, supported by the existing and some additional ceiling chords.
I commissioned a report from a structural engineer who advises that with the correct reinforcement to the chords and lowest beam, this is both possible and safe. This can be achieved by forming a ‘flitch beam' (i.e. adding a 10mm steel plate with two staggered rows of bolt holes, sandwiched between another identical beam and held together with M12 bolts).
The existing ceiling chords will be bolted to the joists with M12 bolts.
The South-West aspect of the building has two large “up and over” garage doors which will need immobilising, sealing and damping.Then the gaps will be framed with timber, insulated with rock wool and an inner wall of one layer of 12.5mm cement board and one layer of 18mm OSB with green ‘glue’ in between.
The inner leaf structure will be a conventional stud frame clad with one layer of 18mm OSB and one layer of 12.5mm cement fibre board with green ’glue’ in between to form the inner wall, anchored to the concrete floor with an air gap of at least 30 centimetres between the leaves, which will be loosely filled with rock wool.
The frame will need to be reinforced on either side of the main beam with two steel 152x89x16mm universal beams in order to support the inner ceiling in a single span. These will need to be pre-drilled in order to attach the connecting timbers.
The inner leaf ceiling will be built using an ‘inside - out” design. The ‘backbone’ will support timber framed modules which will be capped with one layer of 12.5mm cement board and one layer of 18mm OSB with green ‘glue’ in between.
The existing window will be replaced on the outer leaf with a fixed one, glazed with 21mm laminated glass and one on the inner leaf using 12mm glass, conforming as closely as possible to the design in chapter 5 of the second edition of Rod Gervais’s book. The existing door will be removed and two, triple sealed doors (similar to Rod’s “super door”) will be installed with closers.
I have spent a lot of time considering the ventilation requirements of the space and my calculations suggest that the the supply ventilation path should consist of a 200mm x 200mm outer louvre fixed to a plenum box and then approximately 75cm of 6”diameter round duct which will be connected (via a 6” sleeve) to an outer leaf silencer box made of 25mm MDF, lined with 25mm of duct liner, with a cross sectional area of 100 in² (645.16 cm²) throughout and incorporating 8 x 90 degree turns. This will penetrate the outer leaf and feed into another run of 6” round duct (approx 100cm) which will connect to a larger, inner leaf silencer, similar in design to the outer leaf silencer, but increased in size to allow a CSA of 144 in² (929 cm²). This will penetrate the inner leaf at head height, adjacent to the mini-split inner unit, via a deflection grill.
The exhaust ventilation path will be similar only in reverse, with the important difference that it will include an inline fan sized to provide the correct airflow pressure and velocity and powerful enough to cope with the static pressure in the ducts and silencers.
I know that the limited space will make acoustic treatment more difficult - I intend to put bass traps in the two windowless corners and attempt to create a variable acoustic using dual purpose absorber / reflectors which can be moved along wall mounted rails or used as free-standing units on the floor, depending on the desired environment.
I’m sure there is much I have overlooked in this and other areas, any thoughts on how to improve my design will be gratefully received and valued.
Thank you for reading this post and best wishes. John.