Does photo show that green algae/(mold) under deck has spread to house floor?

[Plupp 290759]

Hello.

see photos grateful for help/input.
have had the house for over 10 years.
can the green be washed away with vinegar or weed vinegar considering that the beams under the house have become green? shouldn't these floor beams/boards be pressure impregnated?
The decking boards under the deck in the foundation suddenly all really green with algae or mold. ?
Boards, beams
that create the house's floor underneath when you look up -seem to have become a little green too. see photo.
how is this possible?
how can the house become green underneath when you look at the floorboards/panels under the house?

the deck has been there for over 10 years. I wash it every year with vinegar for algae, but suddenly everything under the deck turned green.
the house stands on higher pillars so the wind can ventilate under the house.

 

[1977bjorn]

Looks like completely normal algae/moss. Apparently, you have the right conditions for it to thrive there. It's not mold! I wouldn't worry.

I would never have the energy to do the following, but if you really want to...

If you can access it from underneath, you can wash it off with decking cleaner. Let it dry. Then treat with iron sulfate mixed in water (note, it will stain the wood gray, so if you spray it, there's a risk of discoloration on the top side). This will prevent growth for a longer period, hard to say how long, but algae/moss don't like iron.

 

[Plupp 290759]

Looks like regular algae/moss. You apparently have the right conditions for it to thrive there. It’s not mold! I wouldn't worry.

I would never have had the energy to do the following, but if you really want to...

If you have access underneath, you can wash it away with deck cleaner. Let it dry. Then treat with iron sulfate mixed in water (note, it will stain the wood gray, so if you spray it on, there’s a risk of discoloration on the top side). This will prevent growth for a longer period, hard to say how long, but algae/moss doesn't like iron.

reply from me:

Thanks! Shouldn't the wood be pressure-treated?
I have cleaned with vinegar on top of the deck, which removes green algae directly,
but I've never tried iron sulfate - what type of sprayer is used, or do you apply
the iron sulfate with a brush?

 

[1977bjorn]

reply from me:

thanks! shouldn't the wood be pressure-treated?
I've washed the top of the deck with vinegar, which removes green algae directly,
but I've never tried iron sulfate - what type of sprayer is used or is iron sulfate applied with a brush?

so, I've never washed my decking from underneath. It was just a tip based on the fact that iron sulfate and algae don't go well together. You can clearly see that your own treatment has run down and dissolved the deposits in some places. You can apply iron sulfate mixture with a regular pressure sprayer from Biltema. If it mists out, there's a risk you'll get the mixture in places you don't want it. Brushing works well too.

As mentioned, not something I would personally spend time on.

It looks like the support beams are pressure-treated, yes. That doesn't seem to prevent algae from attacking. However, pressure-treated wood, depending on its classification, should last a long time anyway, even if exposed to moisture.

I cut away a piece of our deck this summer due to renovation. It looked really rough on the surface. In the saw cut, it was extra clear that it was just the surface that was rough. Far from needing to be discarded in other words.

 

[Stefan1972]

Let it be, it sounds like you're worrying unnecessarily as it's not about any mold that can spread. Additionally, pressure treatment is a method to make the wood last a bit longer. It does not prevent moss, algae, or mold for that matter from growing on it. What you're showing in those pictures is completely normal, and it probably looks the same on the underside of many decks and similar structures exposed to moisture.

 

[Plupp 290759]

So, I have never washed my deck underneath. It was just a tip based on the fact that iron sulfate and algae don't mix well. You can clearly see that your own treatment has run down and dissolved the deposits in some places. You can apply an iron sulfate mixture with a regular pressure sprayer from Biltema. If it sprays out, there is a risk that you get the mixture in places where you don't want it. Brushing works well too.

As I said, nothing I would personally spend time on.

They appear to be pressure-treated beams, yes. It doesn't seem to prevent algae from attacking. However, pressure-treated wood, depending on classification, should still last a long time, even if exposed to moisture.

Reply to your post:
I am so happy and grateful for your answer - I'm just about to try to get someone to remove the entire deck on pillars that go around the whole house - tear down the stuff. We homeowners often have a poor economy... Do you mean that because I did as everyone suggested, washing with weed vinegar from Biltema in a jug to remove green algae on top of the decking (great quick result), this may have run down between the deck boards to the underneath and created problems? As you said, they might have poor pressure treatment.

I cut away a part of our deck this summer due to remodeling. It looked really worn on the surface. In the sawcut, you could see extra clearly that it was just the surface that was worn. Far from needing to be discarded, in other words