Stopping everything from rusting.

Hi, my workshop is a pre-fab concrete garage with asbestos roof.
I am having problems with everything rusting. I have a small heater to try and up the temperature slightly, but I’m losing all the heat. I’m going to seal the gaps between the asbestos and walls with expanding foam. I’m wondering if insulating the roof with 2” sheet will help a lot, or will that be a pointless exercise?

Thanks.

Your roof will be leaking nearly all of the heat and have the biggest temperature differential. Insulate the underside of that and your rusting problems will be severely diminished.

I know this isn't going to help much, but I had one of those garages at a previous house and it was the worst thing I've come across for stuff rusting.

Possibly making an insulated ceiling and insulating the walls may help a bit, in effect creating an insulated inner box that you can heat / de-humidify more easily.

Rob

asbestos roof. Any insulation will improve matters.

small heater How small and what is the energy source? Any fuel-burning heaters would produce some water.

losing all the heat You are not alone. Every building loses exactly all the heat put into it - sooner or later. The trick is to slow down that heat loss.

Insulation, draught-proofing, dehumidifying and some warmth is necessary to.avoid the condensation which is causing the rusting. Consider the value of your machines and decide whether you wish to ‘lose’ them when deciding on how much to invest in preserving them. My capital costs were quite high, but the running costs are acceptable and low. The running costs would already have cost more if the insulation and draught-proofing were not indtalled.🙂

My heavily insulated, draught-proofed workshop now has a Chinese Diesel air Heater to help keep the contents, as well as the space, warm. The desiccant dehumidifier is currently only running one hour (on the low setting of 375W) during the E7 period and the CDH is run for while I am in residence, or for a little longer (I set it to run for as long as I think necessary when I vacate the workshop).

The insulation was all secondhand (as were the non-working dehumidifiers I bought and repaired) and the oil I am burning was purchased some time ago. The CDH runs from an old battery which is permanently connected to a float charger.

Asbestos roofs leak heat and it cause condensation to collect there and drip. Insulation is the thing to do either replace the roof or install an insulation layer below the existing roof. We had one similar at work and that also leaked under the wall when it rained as well. We had to lift the sections and seal under each panel, replace the roof with an insulated metal corrugated sheet type and then sheeted the inside walls with indulation and ply wood.

David

If you block the ventilation gaps with spray foam the roof will run with condensation.

If the slab extends outside the walls the rain will come under the walls.

8 x 4 sheets of foam are not expensive, Wikes sell it for £11 a sheet 25mm thick, sealing the roof off with it will not be pointless. However, most of the damp comes from the floor so applying a big sheet of membrane and then screeding over it will be needed.

Sealing things up too well hampers ventilation

My sealed garage is like a barn with the wind whistling through the big doorframe top and bottom

10 years now and no issues

My current newer warmer type house has had condensation issues in the past but we learnt to ventilate during the daytime and these issues disappeared

No condensation issues in the tenements of my childhood either, because the wind whistled right through those damned places

When I work in the garage in winter I'm wrapped up for the outdoors, if it's too cold to start with I do cleaning work to warm up properly, hoovering etc

Edited By Ady1 on 04/12/2022 17:24:13

There have been quite a few threads in the past on this subject. Try the search option on the hme page, not the one on this page.
The condensation dripping off the roof will soak into fiberglass type insulation so bear that in mind. Ideally you want inside>waterproof layer>insulation>drip catcher>ventilated air gap for condensation to leave> roof sheets. therefore it may be better to put in the insulation as a continuous layer below the rafters rather than between. Any gap in the waterproof layer allows moist air to pass either from inside or outside depending on season. It is important not to let the insulation get damp or it just sits there absorbing your heat to evaporate the water.

As a stop gap cover all machines with a cotton not synthetic sheet (jumble sale) and if available a blanket over that. Not plastic sheet which sweats. This catches the dew which does actually form even inside a building.
Make a box or shed within a shed for all small tools, or a cabinet or shelves to gather things into a smaller space, insulated if possible, and heat just that.
If you can spare the headroom, at least for this winter, a few pieces or 8x4ft OSB will make a 'room' leaving say1 ft clearance above. This will give you space to put an insulating layer on top and in this case I would put a plastic sheet over that insulation to catch the drips off the roof.
Apply diluted clear Waxoyle to all stock material and tools thinned with white spirit so it dries to a slightly tacky wax. It is much nicer to handle than oil. You can treat the whole lathe too as ail will wash it off bits that need oil.

On the other hand, my fully insulated workshop has no ventilation whatever and I don't suffer any rusting issues.

The main thing to do is reduce the temperature differential to a minimum. If you can't do that, do your best and stay ventilated.

As many will know i built a fully insulated fridge panel type garage /workshop. I still have the dehumidifier running through the winter months. I get about a litre of water out every 3 or 4 days. Probably coming through the concrete base.

At my previous house i insulated the garage door with polystyrene panels , which helped. A friend had a company in who fully spray lined the garage with insulation. That was toasty warm, but probably very expensive.

Brother in law had a concrete garage with wriggly asbestos roof. He bought large sheets of poly insulation from the.. builders merchants. He did all the roof & the concrete walls. The walls he then oversheeted with ply . It worked well.

Edit... I still spray coat some cutters & other tools with the shield stuff but i guess these days it is banned. 

Steve.

Edited By Steviegtr on 04/12/2022 20:59:31

Edited By Steviegtr on 04/12/2022 21:00:27

Edited By Steviegtr on 04/12/2022 21:01:16

My workshop is single skin brick with concrete flag floor. I sealed my base with mastic asphalt, not a job you can do yourself, but you finish up with an impervious flat clean finish. However, my base didn't go under the walls, so rain couldn't get under, not sure what the effect would be. For the walls I built an inside out shed, 3*2 framework with insulation between and lined with sheet material. Don't forget vapour barrier between cladding and insulation. The roof is another issue for which I don't offer a solution. With profiled steel roofing you can get panels with a thin layer of insulation bonded on, this keeps the wet air away from the cold steel and is supposed to stop condensation, but it would be a major undertaking to replace your roof.

Workshop before that was a draughty precast garage, I couldn't stop condensation either. Ventilation didn't help if the weather changed from cold and dry to warm and wet the wet air got in and condensed on the cold machines. I sort of controlled rust by spraying everything with Duck Oil, but it is very messy.

Wooden shed. Roof, walls and door all completely covered with roofing felt to keep rain off wooden structure, so waterproof. 3 ply sheets on interior walls. Void stuffed with loft insulation. Roof lined with polystyrene panels glued in place with overlapping joints. Tubular heater +thermostat + timer on lathe. Timed off during the daylight hours. Lathe covered with thin plastic sheet. Mill 1 covered with thick plastic sheet and home made low wattage heater on drip tray. Heater is 4 old style bulbs wired in series on protective box. On 24/7 except when mill in use. Mill 2 covered with thick plastic sheet, no heater. Tools and work left on bench with thin plastic sheet cover, no heater. Tools on open shelves around mill and lathe, no cover or heater. It's that tubular heater that warms the whole workshop with its heat gradually escaping from under the plastic cover. Comfortably warm upon unlocking anytime next day. Concrete floor sealed with black sealant jollop, covered with scrap sheets of hardboard with old redundant car mats. Wooden walled shed stands on brick walls, 3 courses. Felt overlaps brick wall base. Windows boarded up. Small wooden frame around inside of door, to which 3 ply glued and screwed and voids stuffed with loft insulation. System works well, just a bugger getting from house to workshop and back in wet/freezing cold. Yes, it does get cold down 'sarf' in Brighton! Shed size, 10 x 8ft, so fairly small volume. Max/min thermometer to keep check on temperature variation.  Humidity gauge to  get some idea of air condition. Got dehumidifier to remove moisture but never use it. Others have said plastic sweats but not if low heating keeps the dew point high enough.

Edited By DMB on 04/12/2022 22:47:39

Edited By DMB on 04/12/2022 22:52:11

Edited By DMB on 04/12/2022 22:55:19

My old workshop was the same type of construction: a 1950s pre-fabricated concrete garage with an asbestos roof, concrete floor and wooden doors. IT suffered from chronic condensation. I gave up trying to do anything with it and replaced it with a wooden garage.

The new building sits on beams on the old garage base and has its own wooden floor. The floor has a sheet of polythene on to stop draughts and is covered with rubber jigsaw matting. The walls have tin-foil bubble wrap stapled on them, covered with chipboard. The roof is just the standard timber with no insulation.

It is unheated and I do not use a dehumidifier.

It was not an expensive garage as my budget was limited, but I no longer have any damp or condensation on tools, the lathe or the Austin Seven that is in pieces in there and it is a much nicer place in which to "work".

If you can afford it, and put up with the upheaval, I would seriously consider spending your money on a replacement building, rather than trying to sort out the existing structure.

Regards,

James.

Edited By James Alford on 05/12/2022 07:49:41

Edited By James Alford on 05/12/2022 07:50:01

Edited By James Alford on 05/12/2022 07:50:36

Edited By James Alford on 05/12/2022 07:53:40

There is something call ‘controlled ventilation’. Much better than uncontrolled draughts.

I sorted that problem (mainly) by screeding the garage floor.

I’m like Pete, there is no ventilation (so no draughts). Humidity is kept under control by use of a dehumidifier.

I wouldn’t consider anything less than 50mm of insulation - mine is now all 100mm or more - although there are some 25mm sheets amongst the mix.

But any insulation helps - it is a balance of cost and effort versus energy requirement reduction in the longer term.

As I see it, the basic mechanism is that warm air holds more water vapour than cold air. The warmer the air, the more water vapour it can hold. Therefore when warmer air is cooled or meets a colder area, it cannot hold all the water vapour any more, so it will condense out. If the colder area is an air mass, you will get fog and clouds. If the colder area is a surface, water vapour will condense onto that, which is how dew forms on your grass. If a surface contains iron, rust can form. Rust needs water, oxygen and iron to form. 

So, to prevent rust, you can ensure your machines are always warmer than the surrounding air - only needs to be a degree warmer.

Or, ensure the air is dry and contains no water vapour.

Or prevent oxygen touching the iron by applying a barrier; e.g. oil, machine wax etc.

A garage made from concrete or similar building materials will wick water through from the outside or the ground. Houses are constructed with damp proof membranes on top of any floor or wall foundation that is in contact with the ground. In addition, houses have a cavity wall, i.e. a double wall with a ventilated gap between them. This gap prevents water from the outside wicking all the way into the inner wall and making that damp. Many garages though, are built without any damp proof membranes and have single-leaf brick or concrete walls. These garages will always potentially be damp, and any iron in them will rust unless it is kept above the dew point and/or the air is constantly dried or warm air is ventilated out.

Wood does not conduct heat or cold as much and does not wick water, (unless it is completely saturated).

This is why those old single leaf pre-fab concrete and asbestos garages are such rust traps, and a car in there will rust more than if it is left outside on the driveway. During the day the air in the garage warms and absorbs moisture from the walls and floor. At night the temperature drops and that moisture condenses out onto the now cold walls and floor, and also onto the car or machines in there - which didn't warm up as much as much as the air did. (The same car on the driveway is constantly very well ventilated). So those old garages either need to be well ventilated and kept as cold as the outside air, or constantly heated, or sealed and constantly dried.

Or build inner walls with a vapour barrier or gap, as many have recommended - to prevent the moisture wicking through to the inside - and insulate to retain a certain air temperature inside.

Edited By John Doe 2 on 05/12/2022 13:10:03

I was wondering if the concrete itself make things worse from a chemical point of view. I'm no chemist so maybe someone with a little more knowledge may like to comment. What I have found is that concrete carbonates by reaction with CO2 in the presence of moisture and produces Sodium biCarbonate which is described as an acid salt so maybe the dampness and the moisture in an enclosed concrete building is better at promoting corrosion due to it's chemical nature than neutral pH dampness. If that is the case then a coating of paint to seal the surface of the concrete walls and floor could help. We need a tame chemist really.

regards Martin

Fortunately I have never had to use such a garage. It appears to be impossible to insulate.

A dumb suggestion: Why not erect a wooden shed within the garage? The garage will keep the worst of the weather off the shed and the shed can be insulated properly.

JA

Martin
Sodium Bicarbonate forms an alkaline solution.
Keith

Don't worry about the heating, just cover the tools in a blanket. It's rapid temperature changes that causes moisture to form on tools and machines, hence the rust. Cold tools in warm air is asking for trouble; the dew point won't be far away.

My Grandfathers ML7 was kept in a completely unheater workshop in the side of an earth bank, with a polycarbonate roof. Not a spot of rust on it or any other tools, an old wool blanket (not plastic, it needs to breathe) draped over it.

I should have said Calcium Bicarbonate which ranges from 6.3 to 10.25 according to the carbonate species (so I’m told by looking it up) so it seems at least possible to generate a mildly acidic vapour. Carbonation of concrete certainly reduces it’s pH to the extent that reinforcing steel work begins to corrode according to the literature.
regards Martin

Edited By Martin Kyte on 05/12/2022 20:04:44