Does this look like dry rot?

[KDMcM]

Hi.

I've recently lifted the carpet which the previous owner installed in my house. To my surprise, there were some really nice looking floorboards. My wife would like them sanded and varnished.

Unfortunately, I found some spindly arms apparently growing up between some boards. At a glance, they look a little like beansprouts, but on closer inspection, they're more like cotton wool, but a lot tougher.

They look organic, but I don't know. They don't look like any of the other dry rot photos I've seen on Google. The green you see is simply remnants of the underlay. The white bits are the worrying part.

(Click photos below.)



The floorboards are on the ground floor. There's about 10 inch clearance between the boards and the ground. there is a vent installed in the floor (venting into the room) but only one, and it's at the far end of the room (appx 6m away).

Has anyone seen this kind of formation before? Should I be concerned? Is it fungal? Can I treat it?

I had read that (if it is dry rot) it can be killed by the absence of moisture. Would an additional vent at the opposite end of the room help?

Many thanks!

 

[vinn]

First glance says its all remnants of underlay but to be a more sure and to have a look at the sub-area why not lift a couple of boards - I can see a screw, and a nail, face fixing the boards to a joist.

Is the vent you mention venting above the floor into the room - or below the floor into the sub-area ie. its an air brick?

How do you know there's only 10" of crawl space?

Is the external ground level below the DPC?

 

[KDMcM]

First glance says its all remnants of underlay

I really don't think so. Those beansprouty bits are properly wedged between the boards and not similar to the (sort of rubbery) underlay which had been there.

but to be a more sure and to have a look at the sub-area why not lift a couple of boards - I can see a screw, and a nail, face fixing the boards to a joist.

Trying to minimise the damage. Yes, this screw is attaching the board to a joist, but the board hasn't been cut / lifted. it may have been a squeaky one and someone has put a screw in to fix it. I'll try not to lift them unless alarm bells ring!

Is the vent you mention venting above the floor into the room - or below the floor into the sub-area ie. its an air brick?

I think air bricks normally vent the underfloor to the outside? The vent I have is in the floor, allowing air to pass between the underfloor and the room.

How do you know there's only 10" of crawl space?

Long story. It looks like the room used to be two, separated by double doors. On either side of these doors was a brick pier. These piers were demolished at some point and the brick made level with the flooring. I've chiselled away the levelling, in the hopes of replacing it with some pieces of T&G. In doing so, I can see the ground. Granted, my "excavation" is about 2m away from the offending "growth"!

Is the external ground level below the DPC?

Yes, external ground level is appx 3 bricks below DPC.

Thanks for your time and patience.

 

[vinn]

Your house, your call but the best practice would be to lift boards on both sides of the knock through.
Why, because you may have non-ventilated compartments under the floor(s) in both room(s). Lack of ventilation allows condensation & condensation is grounds for rot.

No matter the results of the dry rot investigation it pays long term to provide through ventilation from one side of the house to the other, & to know the state of the sub-area joisting esp. where the joist tails sit in wall pockets.

Lifting boards near to joist bearing/external walls is best & easiest.

All surface exposed fixing heads will have to be sunk or removed before any sanding takes place.

The separate issue of the masonry between the wood floors can be dealt with later if you want?

 

[KDMcM]

Your house, your call but the best practice would be to lift boards on both sides of the knock through.

Personally, I would have done. Previous owner did this job. There's a number of erm... "DIY styles" here. Some good, some bad.

Why, because you may have non-ventilated compartments under the floor(s) in both room(s). Lack of ventilation allows condensation & condensation is grounds for rot.

Naturally. Sod it. I think I'd prefer another scar in the floor rather than me foot going through it one day!

No matter the results of the dry rot investigation it pays long term to provide through ventilation from one side of the house to the other, & to know the state of the sub-area joisting esp. where the joist tails sit in wall pockets.

I can't imagine why there's only a vent at one end. My last house had the underfloor vented to the outside at both ends.

Lifting boards near to joist bearing/external walls is best & easiest.All surface exposed fixing heads will have to be sunk or removed before any sanding takes place.

Yeah, done floors before. I'll take the screws out and nail them and sink the heads.

The separate issue of the masonry between the wood floors can be dealt with later if you want?

Would love to hear any tips - at the moment, spouse has decided to make a bit of a feature of them.

 

[endecotp]

I think it's some sort of string-like material that has been stuffed into the gap between the boards for draughtproofing.
It's not dry rot.

 

[KDMcM]

I think it's some sort of string-like material that has been stuffed into the gap between the boards for draughtproofing.

That was my first thought, and it IS predominant in the bigger gaps. But it just looks like cotton. It looks ... organic, or something.

It's not dry rot.

I'd like for you to be right!

 

[ajstoneservices]

I'd like for you to be right!

He is.

 

[Seafarer1966]

If you have a good cross flow of air underneath your floor boards you won't get dry rot.

Dry rot is a fungus and the spores thrive in still air i.e. where there is no breeze at all. The more air bricks the better.

The item looks like man made fibres.

 

[KDMcM]

Funny you should mention tropical fish. The previous owner had several tanks at this end of the room. I'm pretty one was leaky because one of the electrical socket back-boxes is rusty. I wonder if some moisture hasn't crept under the floor. There's no staining. I hope I'm just being paranoid.

 

[theprinceofdarkness]

I would hope its home made caulking to seal the gaps between the boards. From memory, dry rot has cracks across the grain in the affected area, not like this at all. I was going to mention caulking the boards. I have not seen any ready made stuff, Its got to be flexible, not too white and needs to accommadate gaps from, .5 to 6mm and if its easy to use, ... I was thinking of cotton wool soaked in a dilute PVA glue, left to go tacky then knifed in. Knot holes must be dealt with as individuals. Sounds as though your under floor ventilation could do with improving and at the same time underfloor insulation should be installed. It is turning into quite a project!
Frank

 

[Seafarer1966]

Now that I have looked at your photos again I am pretty sure that the green stuff is underlay that has been glued down. I had a hell of a job on my hands and knees scraping the same stuff off one of my floors where a carpet fitter had been over enthusiastic with the spray adhesive.

 

[Diver Fred]

The white bits look like plant roots. As the adjacent floor board is screwed down lift the board and properly investigate.

 

[KDMcM]

From memory, dry rot has cracks across the grain in the affected area, not like this at all.

I think that's only after it has absorbed all the moisture.

I was going to mention caulking the boards. I have not seen any ready made stuff, Its got to be flexible, not too white and needs to accommadate gaps from, .5 to 6mm and if its easy to use, ... I was thinking of cotton wool soaked in a dilute PVA glue, left to go tacky then knifed in.

When I did this last time, I made papier mache with brown cardboard soaked in PVA. It worked really well.

It is turning into quite a project!

Tell me about it. Same with all DIY...

 

[KDMcM]

Now that I have looked at your photos again I am pretty sure that the green stuff is underlay that has been glued down.

Per my original post, so am I.