Hi, I’m building a garden music practice room and have a question regarding ventilation, my space will be about 10 ft x 11 ft in size and about 7 ft ceiling height, I will be having a 4 ft wide French door and around a 2 ft x 1 ft wide window, both will be double glazed units, the room will come under permitted devolpmet but will be build as close to building regulations as possible to provide a stable environment for a piano etc…,

How much ventilation will this size room require? Would adding trickle vents to both the French door and the window be enough? Or should I add an extra wall vent or a powerd vent?
Thanks for any info given.

  • Adam

    To answer your question fully we would need a few more details from you relating to the method of construction you intend to use.

    Will it be bricks and mortar? A flat pack ‘shed’ type structure or a prefabricated piece from a supplier? What sort of foundation will it sit on? If it has a solid floor (slab) you should be ok with just the ventilation from the windows. If it is a suspended (wooden joists) floor then you will need air bricks in the brickwork base to allow enough ventilation to help prevent conditions ideal for rot and fungal growth.

    Will it be insulated? If you are planning to use it for music you may wish to look into acoustic insulation as well depending on how close the house and your neighbours are.

    If you can more clearly describe how you plan to construct the room we could give you better guidance.

    Rule of thumb though; modern regs only really require mechanical ventilation in rooms such as kitchens, utility rooms and bathrooms as they tend to have sources of heat and steam within them. Warm, moist air is what causes most problems for a house and so need removing via efficient means (vents). Most other rooms are sufficiently vented with trickle vents and general air flow (opening of windows and doors)

    As long as you don’t plan to take a bath in there before you practice you should be just fine with trickle vents. That said its easier (and cheaper) to add a vent at the construction stage than after the fact. You never know if you might change the use of the room in future so considering one at this stage might be wise.

  • andy p

    hi, thanks for your reply,
    here is some more info

    i am using a concrete slab as the foundation on top of which will be bolted a 3×2 timber frame
    with osb3 sheeting on the outside, breather membrane and then batons to attach the Finnish,
    insulation will be between stud work using 75mm acoustic rockwool RW3 over which a vapor barrier will be attached then 12mm plasterboard and skim.

  • Adam

    Thanks for the extra details Andy.

    Firstly I want to deal with the slab foundations. What damp proof membrane do you propose to use to prevent the timber frame from getting wet? Bolting the timber directly to the concrete will penetrate any DPM you may have in place. It might be advisable to construct your timber frame on a series of single brick "walls" which you can then place a DPM and then your timber frame onto. With timber especially, damp is your no1 enemy.

    The exterior sheeting with membrane sounds right. Be sure to overlap the membrane by the required amount. It will be clearly marked on the membrane. Do not be tempted to lessen the overlap to save yourself a few quid if it’s a close fit. You can buy the membranes in various roll sizes and widths. Do the math first to make sure you get what you need and remain cost effective. In this instance I would say that a quality membrane is very important. Tyvek is a recognised industry favourite.
    Remember to hang horizontally not vertically! You’ll need a second pair of hands at least to make this job a bit easier.

    Make sure your batons are at least 2×2 to allow roughly a 50mm airgap between the cladding and the osb.

    I’m a bit rusty with the internal vapour barrier. It depends on a few things like whether you are building your roof as a cold deck/warm deck and if you are using foil backed plasterboard or not. You’ll need to do some detective work on that one.

    Depending on how soundproof you want this room you may need to consider greater levels of acoustic damping. "Acoustic" rockwool talks the great talk but doesn’t walk the walk when it comes to loud noise I’m afraid. Density is king in these instances. Double plasterboard or a specialist foam wall covering are two possible ways of reducing noise transmission.

    Hope some of this is of use. There is lots of useful construction advice on the web for this sort of project if you hunt around for it. The best rule of thumb is that is cheaper to add something now if you think you may need it in future than retrospectively. You usually get a neater finish too.

    Good luck.

  • andy p

    Hi, regarding the dpm for the bolted frame I intend to use a liquid dpm such as black jack everbuild dpm or similar product as is seems ideal for the job.

    Regarding the roof I am aiming for a pent roof, is it nesesary to vent the roof space? I wasn’t sure if to fully fill with insulation, vapour barrier as before, the roof Finnish will be rubber EDPM over osb3 would this cause problems? I’m not up to speed on roofing requirements

    Thanks for the the help and information I will take everything into account with my planning.

  • Adam

    The blackjack will suffice as a dpm but be sure the structure overhangs the slab so you don’t drip onto the slab. Any sitting water will end up on top of the blackjack and be soaked up. The same is true of water that is blown under the building by the weather. Make sure your design is such that water is prevented from getting under the structure as much as possible or devise another way of getting the subframe off the slab.

    A pent roof will be fine. If you are planning to insulate and have a vapour barrier you should also have an air movement gap for ventilation purposes. Treat it the same as you would the walls so 50mm gap.

    The Epdm is fine for the roof covering. Is it being professionally fitted? If you are doing this job yourself then I would recommend also putting down the same breather membrane you used on the walls underneath it. This is a secondary means of protection in case the joints fail. Which they do. Don’t forget to lap the membrane over the roof edge and down over the first run on the walls.

    For ventilation purposes fit vented soffits to the roof overhang and you should be just fine. These are cheap and readily available in 4 or 5m lengths at your local building plastics specialist. Check your local industrial estate for one.

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