Shed weathering/mold

guspage · February 2023

Hi all

Our shed has discoloured over winter. Not sure if it is mold or weathering, the wood still feels firm. Shed is a couple of years old, it came treated from the factory then I treated it at the end of summer 2022. Do you think it is mold or weathering and how would you go about fixing it. Some suggestions so far are a bleach scrub or a pressure washer. I've included pics of the discoloration and the stuff I used to treat the shed. Thanks in advance for any advice.

rowlandscastle444 · February 2023

My shed gets discoloured, along with the fence, regularly, and I treat them every other year. It's a lot of work, but it's worth it. I always use a stiff dry brush to remove much of the discoloration, then repaint. Never had a problem. Most of the discoloration I find is lower down, or on the north facing sides.

guspage · February 2023

@rowlandscastle444 do you use a fungicide too when you repaint the shed?

rowlandscastle444 · February 2023

I know that I will get criticised for this, but I use Ronseal One Coat Fence Paint - Forest Green!! Actually, it was my wife who said she preferred green to brown. I must admit it helps blend in with all the greens of plants, and is easier on the eye.
But as to whether or not it contains fungicide, I suspect not.

philippasmith2 · February 2023

If the wood was pressure treated, then a simple wood stain should be all that is required. Like any timber structure, regular cleaning and maintenance is necessary.
Is there adequate ventilation and have you checked the roof for leaks and the floor for rising damp ? All wood will eventually "weather" on the exterior - more noticeable on a wet/windy site.

rowlandscastle444 · February 2023

Just checked on the Ronseal webpage. It does NOT indicate that it contains fungicide. So, no, I don't use one.

guspage · February 2023

Hi @philippasmith2. Yes definitely enough ventilation. It is definitely a lot more pronounced on the sides of the shed that are more exposed. Perhaps it is just weathering, I was worried it might be mold. I'll definitely be cleaning and staining it again this (and every) summer.

rowlandscastle444 · February 2023

rowlandscastle444 said:

My shed gets discoloured, along with the fence, regularly, and I treat them every other year. It's a lot of work, but it's worth it. I always use a stiff dry brush to remove much of the discoloration, then repaint. Never had a problem. Most of the discoloration I find is lower down, or on the north facing sides.

MikeOxgreen · February 2023

Don't do anything until late Summer/early Autumn, the wood is too damp now.
By then the wood will have dried out, the Summer sun done its damage to the coating and you can rub down and re-coat in time for Winter and next year.

People think Winter damages wood protection, but it doesn't. It's the sun (UV) which breaks it down, then the rain gets in after.
Don't powerwash it!
I can't comment on what has happened as I don't recognise that stuff, know what the shed was treated with originally or what it was like before it was re-coated by you.
I would stick to a better known brand such as Sadolins perhaps in the future.

Always coat wood before it deteriorates, by the time it does it's too late.

bédé · February 2023

Eventually any stain or surface coating will weaken and let in UV, to bleach the wood, and damp to feed fungi. Only a good sanding will remove the discoloration. And at least an annual retreatment.

You could admit defeat and go for a less formal finish.

rowlandcastle's green is merely moss/mildew/mould on damp wood and can be scrubbed off, with bleach. The side that gets the sun will be drier. The gravel/soil is perhaps in contact with the wood and is best pulled back a bit to improve air circulation.

Shed weathering/mold

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