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    • CommentAuthormcdaddy
    • CommentTimeSep 13th 2016
    I’m looking to make some modest improvements to my garage - one of several similar units in terrace array of garages all of which share a flat roof. The units were probably build in the 80s, are pretty utilitarian & sit in the grounds of the block of flats in which we live.

    The idea is to improve the watertight-ness, minimise the risk of dampness/ condensation, & make the unit bug/rodent free so it can be a genuinely versatile storage space. Ideally we’d like to store clothes, bedding & other delicate items there - albeit we may still require to vacuum seal these.

    The fabric of the building is pretty unsophisticated:

    • Concrete floor
    • Concrete walls panels bolted together - which will be party walls with neighbours
    • Corrugated flat roof (metal)
    • Hormann Up & Over Garage Door (poorly fitting & probably the only major source of water ingress currently)

    I’m at the early stages of deciding what to do, but I see the following as necessary:

    • Seal the walls, and the floor to stop moisture ingress
    • Install new or add secondary door to stop water ingress & improve security
    • Insulate the back wall ceiling and door (the party walls may not require this as the unit is in the middle of the terrace.)
    • Add some sort of passive ventilation roof cowl/ breather vent with insect mesh
    • Dryline walls with product like fermacell with its high racking strength which will allow me to knock up shelving easily.

    There’s no power to the garages, & although I’d like to get a little grid lighting system going, (possibly also running a small fan) I’m conscious that batteries require a separate housing, & then there’s all the battery mgt issues, etc. It may be easier to take a handheld florescent tube lamp down with me if it’s in the hours of darkness

    So my questions:

    Are my plans sufficient to give the improvements we want in terms of water tight/bug tight & are there any simple idiot proof, off grid systems we could use to power a few lights and possibly a fan?

    Thanks in anticipation for any advice.
    • CommentAuthorgyrogear
    • CommentTimeSep 13th 2016
    Why not just use watertight/airtight containers, and leave the structure alone - would cost much less...

    • CommentTimeSep 13th 2016
    Posted By: mcdaddyminimise the risk of dampness/ condensation

    Heating is pretty much required to do that, in conjunction with other measures. Or possibly a dehumidifier.
    • CommentAuthortony
    • CommentTimeSep 13th 2016
    only ventilation would be needed to keep damp, condensation and mould away

    Crucially do not touch the walls floor or ceiling and it will all be OK so long as there is good ventilation and no leaking gutters, roof or flowing in under door.

    I used a single garage just like that as a store for loads of left over and recycled building materials for 19 years, no sign of mould on wood or plasterboard, cardboard bid absorb some moisture but remained unharmed, my roof did drip from time to time too.

    Sealing up and allowing changes in temperature could result in little black, white and multicoloured dots of disappointment
    We found that much of the dampness in our concrete panel garage was from rain/snow blowing through small gaps under the door and at the eaves. Once water is inside, the floor does not slope enough to drain it out, and the only way to dry it out again is leave the door open on sunny days - insecure. Sealing the eaves has helped, sometime I will add rubber strips round the door.

    Not seen any sign of damp coming through walls or floor, i am not planning to seal line or insulate them.

    There is a band of concrete sealing where the wall panels stand on the floor, check if this cracked. The base should be slightly raised above surrounding ground, clear any debris leaves etc that spoil this.

    Have heard of water condensation on inside metal roof, ours has a layer of roof membrane underneath the metal and this is never damp.

    I considered adding a polycarbonate greenhouse/conservatory panel into the roof to get solar heat in, not got round to it yet.

    Got some motion sensitive solar security lights, these would be great for garage.
    • CommentAuthormcdaddy
    • CommentTimeSep 14th 2016
    The consensus appears to be less is more… & as the unit is part of a scheme with, party walls on either side & no power, it makes no sense in me making this a highend garage.

    Tony, the idea of adding insulation to the back, front & ceiling surfaces is to ensure moisture doesn’t condense out onto these areas, say when there’s a sudden drop in the outdoor temp, against the air inside which may still be warm but cooling. Perhaps this is irrelevant if ventilation is good?

    WillinABZ, yes the door requires replacing with something which is more water tight & we may look at the eaves – but I guess that can reduce the ventilation too much. Will have to see…

    Perhaps the answer to maintaining a controlled environment in the garage lies in a box of vermiculite & calcium chloride. Don’t know if anyone saw the press story on this today…apparently it can be used as a sort of thermal store & moisture absorber....

    • CommentAuthortony
    • CommentTimeSep 14th 2016
    I would still say that ventilation is more important than insulation in this case and cannot see a reason to insulate, only possibility is a sarking layer under the roof.
    • CommentAuthorskyewright
    • CommentTimeSep 14th 2016
    Posted By: mcdaddy
    WillinABZ, yes the door requires replacing with something which is more water tight & we may look at the eaves – but I guess that can reduce the ventilation too much. Will have to see…

    For ventilation you want moving air, not the mix of air + water mix that a random leak or gap under a door might produce.

    So, it may be that you end up sealing in places, then making holes in other, better, places (and perhaps having a baffle or hood over the intentional hole, if driving rain is a possibility)?

    As has been said many times with regard to other projects, seal then ventilate?
    • CommentAuthormcdaddy
    • CommentTimeSep 14th 2016
    Thanks guys
    • CommentAuthorGreenfish
    • CommentTimeSep 14th 2016
    only ventilation would be needed to keep damp, condensation and mould away

    I have to question if that is true for all climates. In the warm but damp deep southwest (where as I type my MVHR vented rooms are RH = 77% at 21C), the drafty but water-tight garage managed to grow a coat of black velvet mould on the underside of the MDF shelves over last winter, and all cardboard was soggy. It is vented well enough, but that just makes it as damp inside as the air is out. Also there is bound to be still areas where the drafts don't pass.

    Keep water out for sure, maybe create a warm storage box for things that need minimal temp regulation (e.g. paint that doesn't want to freeze), and do keep things in sealed boxes
    • CommentTimeSep 14th 2016
    Posted By: tonyonly ventilation would be needed to keep damp, condensation and mould away

    That'll be why you never see condensation outside then.
    ''That'll be why you never see condensation outside then.''

    Dew to the lack of water vapour, I suppose...
    • CommentAuthorgyrogear
    • CommentTimeSep 14th 2016
    humidity being relative anyhow...

    I agree with Tony, here on the sunny East coast we only get condensation on lightweight surfaces (grass cars windows) which radiate to the night sky and chill rapidly below air dewpoint. None of those in our concrete garage, except for the steel roof, which is lined inside. Plenty of dry unheated buildings around.

    I have lived in the balmy West and do understand everything staying damp there.

    The problem with the garage door is the raindrops blow against it, and run to its bottom edge, where the wind whips them straight off under the door. Or they make a puddle on the floor then the wind blows that under. Sealing the bottom edge of the door against a threshold should fix this.

    The structure is far from airtight so I don't worry about insufficient ventilation, but could add rain-shielded bug-proof grilles if needed.
    • CommentTimeSep 14th 2016
    Well, I've put clothes in a garage in the eastern part of the country and they've suffered, as did books except in a slightly heated room. Note that garage roofs see the night sky and are generally pretty lightweight. And as we've established in many threads, there are only two effective ways to dispel excess relative humidity. So I know where I would put my money.
    • CommentAuthorDave_07968
    • CommentTimeSep 15th 2016
    Our garage has a door to the back garden at the opposite end from the up and over, and both have big gaps ensuring plenty of airflow, yet the garage itself is fairly damp. Anything on the floor will rot out / go mouldy unless placed on plastic, and some tools rust up even when stored off the ground!
    Just to update that we fitted rubber strip to the bottom edge of the garage door, but not to the sides/top. Has made a huge improvement over this last winter, the garage is much less humid inside. As expected, the rain that used to blow in under the door must have been the main source of damp.
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