Damp under my floor!

[theflyingpig]

Hi all, got to the musty smell today.....check out the growth under the floor 'joists'! Previous owners have tried to stop that moisture in its tracks -, thick plastic over the dirt and wrapped up the walls. No underfloor ventilation at all. Perfect breeding ground....

So, how to ventilate? The room is approx 400mm below the ground outside (driveway to side, slim roadside pavement to front)...
Walls are about a 500mm thick, probably stone though havent investigated yet....
Was looking at telescopic vents , but think the wall is too thick. Occurred to me I could make something similar out of plastic pipe - drill a couple of 40mm core holes through wall and use waste pipe to raise out of ground....
Anyone got a better idea?

 

[jacko555]

Nuke the site from orbit, its the only way to be sure.

Vents on opposing walls. Needs a breeze down there. Should the plastic go? What's the ground water level like? Maybe sump and pump if high.

 

[theflyingpig]

No problem with ground water, and yes, definitely removing the plastic!
It's how to do the vents I'm pondering....

 

[jeds]

Other than simply saying you need to ventilate, there's not enough info or context here to give a decent suggestion. A photo of the external front and rear would help. Maybe do a sketch of the section across the house - front to back - showing any obstacles, the external walls and what is on the outside.

 

[JohnD]

Is there a fireplace with a chimney?

How does the external ground level come to be higher than floor level?

How old is the house?

 

[tell80]

You appear, from the hazy pics, to have a serious infection of true dry rot.
Its not typically a DIY job to deal with the infection.

 

[theflyingpig]

Other than simply saying you need to ventilate, there's not enough info or context here to give a decent suggestion. A photo of the external front and rear would help. Maybe do a sketch of the section across the house - front to back - showing any obstacles, the external walls and what is on the outside.

thanks, I'll take some photos tomorrow

 

[theflyingpig]

You appear, from the hazy pics, to have a serious infection of true dry rot.
Its not typically a DIY job to deal with the infection.

I actually think the fungus is more likely 'wet rot'....it was spread right out underneath the plastic, covering probably 3 square metres. The only timber down there were the floor joists - treated timber and seemingly unharmed by the fungus, and the ancient chipoboard flooring, whcih was very soft and easy to break up. I'm going to spray the whole area.

 

[theflyingpig]

Is there a fireplace with a chimney?

How does the external ground level come to be higher than floor level?

How old is the house?

there is a fireplace and slender stack that goes as far as the loft. the house is perhaps 400 years old in it's oldest parts. it been added to gawd knows how many times...judging by the materials used this floor couldn't be more than perhaps 30 years old. I spent a few hours playing 'hunt the airbrick' this afternoon, but found nothing....though maybe one spot that there might once have been something...

I could feasibly raise the floor level by nearly 100mm - which would bring it to approx the same level as ground outside (not the 400mm I said in first post!

I'm wondering what total size of vent is required? The room is about 20 square metres.

 

[tell80]

OP,
Just curious, why do you think its more likely that you have wet rot?

 

[JohnD]

You could perhaps dig a pit or trench next to the wall and vent through there

You need vents on at least two sides of the house to get airflow, and the pit must be deeper on the outside so it does not fill up with rainwater and run into the house

Relevance of chimney is that in some cases you can put a vent pipe going down under the floor and venting up the chimney

If you use periscope vents they can be on the inside of the house if necessary

 

[theflyingpig]

OP,
Just curious, why do you think its more likely that you have wet rot?

It was really wet under the plastic, it didn't seem to have affected any masonry... It smelt strongly of mushrooms and earth... Everything I read and the images I found pointed to that.
You think otherwise?

 

[theflyingpig]

You could perhaps dig a pit or trench next to the wall and vent through there

You need vents on at least two sides of the house to get airflow, and the pit must be deeper on the outside so it does not fill up with rainwater and run into the house

Relevance of chimney is that in some cases you can put a vent pipe going down under the floor and venting up the chimney

If you use periscope vents they can be on the inside of the house if necessary

Thanks for input. I think periscopes are my best bet here. The room is on the corner of the house (the corner that never sees any sun)... It's roughly 5000 x 5000..... One vent on each wall or two??

 

[JohnD]

One vent every metre is not too many.

 

[Nige F]

You appear, from the hazy pics, t

yet again tell's computer fails - or his eyesight is going