Dry rot....how fast does it rot wood?

[tucomaluco]

We live in a 1925 semi-detached house and in 2023 found that a leaky down pipe appeared to have caused the front door frame and window sill to rot. In August 2023, we repaired the leak and had part of the frame cut away and replaced. Roll forward 18 months and earlier this year we noticed the paint cracking on the inside sill and a joint on the outside. We removed the internal sill and to our horror found the new sill and frame had partly rotted away again! In one corner and showed signs of tendrils of what looks like dry rot. We have removed a small section of plaster and I can see tendrils in some of the mortar joints. Some of these go quite deep. Additionally I scraped off some white mushroom like mould from the side of the frame abutting the brickwork. I am pretty astonished about the speed of the rot in the new wood. In 18 months it has rotted a good 3 inches into the frame. So it looks like the water penetration is not just from the down pipe. Can anyone confirm whether the pictures show dry rot? (Note that the carpenter used fix and foam so a lot of the white u see is the foam not fungus - its the tendrils and the wood that are a worry)

 

[Lacan07]

I wouldn't necessarily worry about what kind of rot it is (Matt is the resident expert), the important thing is its still damp in that area. Are the walls breathable, what kind of floor do you have?

Modern wood is garbage compared to the stuff they used to build your house so I'm not surprised your 2023 fix rotted so quickly.

 

[tucomaluco]

Exterior walls are the original rough rendered/painted. It was re painted with Sandtex around 5 years ago. Wooden floor which also had rot along the same corner which we discovered in 2022 and treated and replaced rotten timber. The carpenter who replaced the frame said it was hard wood and would last for years! The stuff that came out was like balsa wood. I'll never listen to a tradesperson again!! We need to get to the bottom of the damp source. How do you find a decent person to do a survey without trying to rip you off?

 

[Matt Green]

It's certainly a brown rot and probably dry rot (Serpula lacrymans), given the speed of growth. This is why new timber should always be isolated from surrounding masonry when repairing timber after any fungal outbreak.

The wall may well be drying down post-downpipe repair, especially as it is rendered. Expose as much of the surrounding masonry as much as you can for as long as you can stand to allow it to dry and replace any timber isolating it with a DPM, slate, or similar.


M.

 

[tucomaluco]

It's certainly a brown rot and probably dry rot (Serpula lacrymans), given the speed of growth. This is why new timber should always be isolated from surrounding masonry when repairing timber after any fungal outbreak.

The wall may well be drying down post-downpipe repair, especially as it is rendered. Expose as much of the surrounding masonry as much as you can for as long as you can stand to allow it to dry and replace any timber isolating it with a DPM, slate, or similar.


M.

Thanks Matt. Great advice. We have removed the plaster so we can get a better view of what's going on and the main part of the sill is in the wall by a good 4-5 inches and on top of the brick work with no barrier other that foam filler (not sure about why they used this...not breathable AFAIK). Also the side of the frame has 1-2 cm gap and was touching at one point...again no barrier. I am prepared to leave it to dry out for months if necessary as I really want to stop this spreading!! Now to find a good joiner who can splice in new frame. I miss my Dad at these times. He was a joiner until he retired in 2000. Sadly no longer with us