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Painting Wooden Shed: Ceiling Mould & Medium Wear Floor

Hi, have a customer’s shed to paint and need some advice on coatings. It’s currently bare wood, but a bit humid inside as you can see from the ceiling joists. So I need a system to keep that at bay. Customer has stressed that finish doesn’t need to be spectacular, he’s not bothered about having the wood sanded, for example, but he would like it to last! He also would like it in Pottere Clay 2 or nearest (a light Dulux grey, but not stuck on Dulux).

The floor is another issue. He would like it “varnished” in a dark colour (he mentioned mahogany, to hide the marks). Heaviest thing he has in there is lawnmower, but also kids bikes and general storage. To my thinking, it’s better to go a bit overboard on durability just so he’s not calling me in 12 months time saying it’s coming off. Again, bare wood that just needs a clean and light sand.

Suggestions please!

Hmm, reading through other posts perhaps Zinsser Perma White could be a good choice here?

The first step is to try and address the humidity and prevent this source of mould. Otherwise the Perma White, while designed to deal with the sort of surface you are presented with, is just a sticking plaster over the problem.

The floor issue to overcome, I would have thought is the scuff marks that are likely to occur from moving lawnmowers, not so much the adhesion and peeling. Be careful not to get drawn on providing a zero maintenance floor coating, because it will get black marks on it. Carpets are good for preventing that sort of abrasion.

Hi Andy. Spoke to cust today. She said their shed was put up during the heavy rain, but her hubbie has since put some vents in, and she tries to keep the windows open when she can. Not much more they can do, I guess? Belt and braces, use some multicide or bleach on it first?

Regards the floor, I did suggest to her today to consider having the floor black, so def no marks, and not a million miles from mahogany. If she went for this, can you recommend a suitable coating? I’m definitely not promising anything zero maintenance!

Thanks for your comments.

Bedec Acrylic, after knotting? Would I need a layer of coverstain??

I am guessing that a good vapour - open product would be needed on the shed walls (breathable/microporous) to combat the damp/codensation issues. I would worry slightly about the knots bleeding through paint especially with a light colour. I would definitely treat it with a fungicide first.

Paint:Sadolin Superdec is very vapour open although it for exterior use only (biocides and fungicides etc).
If you can persuade the customer to go with a stain, then Osmo are very good,'microporous’and based on natural oils. They have a product called HS - One coat which may suit. You can also use it internally as it has no biocides in it. You will not get a strong colour unless you go with their Natural Oil Woodstain - exterior only again. In both cases you can apply a clear preserver (Wood Protector)first to help with combating fungal issues etc.

Check with the customer first about using ‘exterior grade’ products inside and make him aware of the biocide issue.

Floor - again i would go with something like an Osmo Oil. They have a product called pitch Black (soon to be replaced) which would leave a pretty dark brown finish with just 1 coat. You can then apply a single coat of Osmo Polyx to which you can add a 2k hardener to give it a commercial grade finish.

I am sure there are other finishes similar, but theses are ones i have used and are familiar with. If you need any more info, please do get in touch.


Hi Ben, thanks for your post. Customer wants a colour on the walls and ceilings similar to Potters Clay 2, so I think the Zinsser is tintable and could be a good option there. Knotting twice with Zinsser BIN should be enough, I would have thought.

Out of interest, what fungicide do you use? I have some Dulux Multicide, but their instructions say to leave on for 24 hours then wash off. I love to follow instructions as much as the next man, but who has time for that?

Cust has also agreed to go for black on the floor so he won’t see marks too much.

Hi David,

No real preference for fungides, but i have just had a look at a few and it seems the 24hr thing is pretty standard. I guess you need to give the stuff time to work. If you dont it may come back to haunt you!

Hi, HG Mould Spray looks pretty good, their products are generally well-regarded, and technical sheet doesn’t say anything about 24 hrs.

I’m sure you’re right, but I do find it odd that some products have a long wait time and others don’t. Even technical sheets for some paints say to use diluted bleach, and I’m sure I’ve read somewhere that bleach doesn’t treat the root of the problem.

I should probably build in some time nonetheless. Think I’d need to undercoat in Coverstain first? Never used it, but hear it dries quickly.

Something that’s just occurred to me. Might be obvious to some, but I’ll ask anyway: if I used Coverstain, I was thinking I’d do the ceiling, walls and floor in one day, but now I’m wondering if I should be walking on a Coverstained floor while I put Permawhite on the ceiling and walls the day after?? I’d cover with a plastic-backed sheet, but would even that be a schoolboy error?? I’m in two minds whether to spec it or not…

Right, have some pics!

Before, during and after. Hoovered, washed with ammonia, light sand, Hoover again, primed with Coverstain then two coats of Bedec. Took two days in total, and that’s just the floor.

Of course, now everything’s gone back in cust asks how long to finish ceiling and walls…

Hows this project going? Floor looks too good to walk on now :slight_smile:

It’s going well thanks Andy.

Customer asked me to spend a day on the ceiling and walls. He’d undercoated in Coverstain. I spent 4.5 hours yesterday just getting one coat on. Really thought I’d be able to put two on in one day. Just goes to show how long things take (and why I struggle with pricing sometimes!).

Customer did buy my recommended products though, so walls and ceilings are in Zinsser Exterior PermaWhite tinted to gray. First coat went on really nice actually, it wasn’t as thick as I was expecting. Second coat even better. I wouldn’t have thought shed would take up 5 litres, but it has done best part of.

I do love that floor, it’s really one of the first things I’ve done where I’ve had the substrate from new and been able to recommend some higher-end product and the customer has not gone out and bought his own crappy floor paint.

Clearly, I need to find some richer customers!

On the pricing Andy, do you have a formula for doing insides by the sq m2?

Looks like you are doing a super job. Once you have done a few you could pitch yourself as the local expert, seriously. Blokes and their sheds… man caves… Good customers are ones that value you what you do and pay accordingly for that value. Over time, I am sure you will see how some “rich folks” value their super workers, not :frowning:

formula for pricing is based on timings for each stage of a task averaged out and then converted to m2 or lin m for labour hours, and m2 and lin m for material costs. It has to be YOUR timings though. Work in your costs per m2 or lin m for labour and material, add your profit and thats your rate. If I told you £3/m2 for 2 x emulsioning walls, it should work out comfortable for you, it might put you in the hole though if you dont measure right, or it is a fiddly bathroom and you don’t allow for the lin m cuts.

I used to work as a professional estimator and the companies we priced up for really didn’t know their timings, just hoped that the pricing book rates we gave them were somewhere close to what they could produce.

I was talking to a contractor he reckoned on £1m contracts he either made £50k, broke even or lost £50k, go figure. Know your numbers and you are half way home.

Andy thanks for your comments, I will reflect on them.

While I do that, I wonder what you’d price this at, very roughly? Not asking you to spend any time on it, just ballpark if you can. Cust has just moved in, half their stuff is in their loft, walls and woodwork are generally in good condition. She wants a gold standard job and has mentioned using Little Greene. I have an idea for myself, but I’d be very interested to hear a rough figure for labour and materials from you. Whole house.

House itself, not garage, is 171sqm. I’d really like to get it…

If she’s looking for a “Gold Standard Job” and as you say your estimating is a bit bronzed, I would suggest a day or hourly rate, with materials supplied at cost! Clients is happy as they get materials at book sheet and is overwhelmed at your transparency. You could give her an estimated timescale of how long the job will take. Dont fall in to the trap of under pricing to get the work, its a mugs game.
People pay good money for Gold!

Thanks Russ. I wasn’t sure about your advice at first, but I did speak to her on Friday. Gave her the figure I had in mind, but said we could also work on a day rate basis so if it was less time then she’d pay less. Offered to supply her paints at cost (though if she went LG they don’t offer a discount anyway AFAIK, but I may well call them about that…). She didn’t sound too offended. She does want her work starting soon, and will speak to her husband about the price.

Out of interest, if she did go for Little Greene, is there any reason I couldn’t suggest say using Dulux for her ceilings to keep the cost down? Is there anything amazing about LG shirting? Their calculator says that for 2 coats on 171sqm I’d need 27litres. That’s about £500.

As a rule, if you or the client are specifying Little Greene, why not just use it? The acrylic matt is a premium paint, so you get ease of use, and high opacity - but having said that,you have found a chink in Little Greene armour.

I have seen reports on Shirting, that it is the least good at covering.

For a cheaper equivalent possible 3 coats, why not look at Leyland matt, they would get the colours close, something which Dulux aren’t famous for. Or ask Holmans for an exact match in Manor Coatings matt emulsion.

But otherwise, if LG or any paint is specced, that is the bar that everyone should work to. If it is a Little Greene colour at the core of the spec, then that is different and you can tell clients that the paint choice can widens to those who can supply an appropriate finish AND the exact colour match.

I know you want to do things right, but as a general statement, what you don’t want to be caught in the middle of is a client paying £60 a gallon for LG and seeing Leyland on site, and you haven’t forewarned them or explained why. You say it is for a better finish on the ceiling, but all they might see is you making you an extra £20/gallon on their account.

Going beyond that, F&B were saying that there are a few too many instances of painters taking empty F&B tins along to jobs and decanting cheaper paint into the tin. That is where it gets fraudulent. The lines can get blurred and very easily a short cut or a “practical” substitute can literally become a crime!