I am likely to be made redundant shortly and am looking to upgrade my 6.1m x 3.8m x 2.2/2.3m (internal size) workshop in Scotland to be able to spend more time furniture building, potentially to kick off a new venture should I end up unemployed for a period. I have various power tools and would like to avoid disturbing my neighbours – there are 6 other houses within ~30m, and the closest bedroom is about 8m away. I would like to be able to work in the evenings as well as during the day and after 8ish there is a suburban background noise of ~40dBA with odd cars passing. I’m thinking if I stick to less than ~50dB I should avoid neighbourly disputes.
I used a £20 sound meter and got the following sound levels inside:
o Mitre saw Bosch GCM 8 SJL, 105dBA cutting with 48 tooth cross cut blade (reasonably sharp)
o Table saw Axminster TS 200 with general purpose blade (not very sharp), 95dBA cutting
o Vacuum, Nilfisk Aero 26-21, 76dBA
o Dust extractor, Axminster FM300 2HP, 87dBA
o Router, Dewalt DW 625 with 19mm straight cutter, 101dBA cutting (99.5 on max speed not cutting and 93 on half speed not cutting)
o Planer thicknesser, SIP 01454, 112dBA cutting 120x20mm larch, 105dBA cutting 45x45 pine
At present, I’m getting an average TL of 26dBA measured outside my garage door, 35 dBA outside the French doors/windows, and 45dBA round the back of the workshop.
I am targeting around 55dB TL to bring my loudest tools down to reasonable levels (ignoring the particularly loud planer thicknesser measurement - seems like I need a new quieter tool there
)I’m willing to spend up to ~£2k, although less is of course preferable.
I constructed my workshop around 2 years ago without really planning for soundproofing or reading this forum (oops). It has the following construction:
• Walls:
o Waney edge 22mm overlap cladding
o 25mm battens
o Breather membrane
o C16 4x2 stud frame at 400mm centres filled with 100mm fibreglass insulation
o Internal 11mm OSB3
• Roof
o 1.2mm EPDM membrane
o 11mm OSB3
o 8x2 joists at 400mm centres with 100mm fibreglass on room side and 100mm ventilation space on roof side connected to soffit vents
o Internal plasterboard 12.5mm
• Other features
o 2-off 800mm x 900mm double glazed hardwood windows
o A pair of wooden French doors, 1980mm x 1540mm with full height standard double glazing, a mortice lock and compression seals which could be better in places
o A thin (<10mm thk) electric roller garage door
My initial plan is effectively a room in a room, which would be mostly self-built. I’ve priced up materials at about £1850 for the below (got a few free fire doors which helped) and would lose ~100mm wall thickness all round. I value natural light, hence have kept windows and doors in this plan.
• Remove the roller garage door and replace with a wall to roughly match existing – I may want to add a set of sealed double fire doors here to give me outfeed for the tools when required and easier access for long boards, but I know sealing doors is time consuming and tricky
• Remove existing electrical outlets and plug gaps
• Add a layer of 12.5mm plasterboard to all existing internal wall/ceiling surfaces
• Build an internal stud wall using 38x68 CLS at 400 centres with 1 set of noggins and a 12mm gap to the wall surface
• Use 60x30x3 steel rectangular tube at 600 centres supported on stud wall with 12mm gap to the ceiling
• Fill with 50mm fibreglass insulation
• Line internally with 12.5mm plasterboard and tape and fill
• Add a pair of internal 30min fire doors with 10mm toughened glass panels to give me double French doors. Use Norsound 710 seals with a rebate all round to avoid tricky threshold seals
• Seal the existing openable windows closed, plug the vents with sealant and add 10mm toughened glass panel to internal wall window opening
• Surface mounted electrics to avoid penetrations through the plasterboard
• If necessary, add 2-off vents ~4-6” diameter with internal and external silencer boxes along the lines of a basic design I saw by Greg on this forum (18mm mdf baffles for internal, 18mm osb baffles plus larch clad for external and using 19mm/25mm Armaflex lining). Use a small inline fan on the exhaust to keep air moving.
My questions are:
1. Regarding frequency measurement, is this useful/valid data? Would you agree with my assertion about the sounds being mainly high frequency?
2. Does this plan seem like overkill to achieve my aims given that my existing walls seem to be only ~10dB away from my target?
a. Could I get away with just adding secondary FD30 fire doors, 10mm secondary glazing, replacing the garage door with wall and adding 2 sheets of internal 12.5mm plasterboard all round? I’m not too keen on resilient bar in the walls since it’ll stop me mounting cabinets and racks etc. If I assume current wall mass around 20kg/m2 then using the mass law for 2200Hz gives me my measured wall TL of ~45dBA. If I increase mass to 36kg/m2 (2 sheets of regular plasterboard), then I seem to only get another 5dB TL at the same frequency, so doesn’t seem like this will achieve the target if my approach is right. I'm assuming I've effectively got a single leaf, since my outer cladding etc is not sealed.
b. Would the addition of green glue and putty fillers for electrical outlets make this work? (I think I could do this for around £1500 in materials including £500 of green glue) – this would also save about 75mm of space all around and should be less work, so is quite appealing if I had confidence in would work
3. Is the standard 4mm/4mm double glazing on existing doors/windows a problem with regards triple leaf at the frequencies I'm interested in?
4. Does 10mm toughened glass for an internal leaf seem about right?
5. Would stiff steel ceiling members compromise soundproofing by transferring vibration easily? If so, would it be worthwhile trying to damp these with some kind of stick on membrane (tecsound or similar?)
6. Are there other options I should think about?