Dry rot or wet rot?

[johnmichaels]

So having lifted a floor board to take a look while fixing a loose board, I noticed a small amount of rot on the end of a couple of floor joists.

The ground is about 1 foot, or less, below the joists and is a bit wet. The water is just localised to this area, other areas of the sub floor are dry. Perhaps I have a leak, and I will be investigating and solving that, but does this look like wet or dry rot? The brown line coming out along the brick concerns me.

If it is just wet rot, I'll replace the timber myself. If it's dry rot, I'll need to get someone in.

I stuck a pen in the gap next to the edge and the joist and a browny powder came off the joist.

Thanks for any advice!

Images:

http://imgur.com/US1imv5
http://imgur.com/9qExADs
http://imgur.com/yPrP1x7

 

[skhudy]

tiny pictures, need to be bigger

 

[johnmichaels]

Corrected with links, cheers

 

[gregers]

going by the pics to me it looks like wet rot.

 

[ree]

As above, its wet rot.

You will have to cut back beyond all staining, and open up the pockets in the brickwork for ventilation. Slice a bit of brick off either side of the pocket.

Wrap the new joist tails in DPC material and clean the pockets with anti-fungal liquid.

Make sure all air bricks are sufficient and are cleaned out.

Dont leave any cellulose debris on the oversite.

Ref the standing water, check on the outside area for possible causes.

Crawl the whole subarea checking for similar conditions.

 

[johnmichaels]

Thanks for the comments and the advice on fixing the problem.

How old does this rot look to you? The reason I ask is that in the last couple of months we've had a problem with the central heating system losing pressure, and so now I'm wondering if there might be a subfloor leak of the central heating system.

However, to me the rot looks older than that. I live in an area that has a high water table, and the ground is pretty saturated at the moment with heavy rainfall recently, so the water could also be ground water...

 

[ree]

Its been coming on, most probably, since the joist tails were bricked into the pockets.

Are your joists sitting above the outside ground level? Do you have solid walls?

 

[johnmichaels]

I imagine the brick pockets have been there since the house was built in the 1950s. All joists in all rooms seem to be like this.

The joists are above outside ground level, however this is an internal wall (which separates the dining room and the kitchen).

All walls are solid brick.

 

[ree]

"All joists in all rooms " do you mean that the joists are tightly built in, or that they all have fungal damage?

Given that its an internal wall then it would appear that it doesn't have a DPC. Can you spot one? Can you spot a DPC on the outside walls?

Is this sub-floor internal area in the pic well ventilated?

 

[gregers]

is there any sign of a wallplate built into the wall aswell?
if so then this may well be rotton.
if not and the joist ends are all built in then you need to do the screwdriver test.
see how far you can push it in ooer missus if its really easy then your going to have to do repairs.
various options,cut back,sister new joist with bolts and knock out holes for the new joist ends.
or
before cutting back,inspect the oversite/footings,we used to knock off the middle half brick of the stepped footing and build a new sleeper wall with a wall plate,if you go down this route you will need to jack the floor up before cutting the joist ends build the wall etc and then when all is set lower the floor onto the new plate.

whatever route you decide to go down the surrounding area/s will need for peace of mind a liberal spraying of a fungicide solution.
also update any airbricks you have and add more if you can.

 

[johnmichaels]

ree - I meant all joist ends in all rooms sit in the wall, not that they're all rotten.

The house is a 1950s semi-detatched build. As far as I can tell the joists and floorboards are all original (or at least haven't been replaced in 10 years+).

All downstairs flooring has joists spanning the room, resting in holes in the walls (directly touching brick or resting on a cushion of slate), and also resting on sub floor walls evenly spaced across the sub floor. These walls are 'half-bricked' to let air flow through (don't know the technical term, sorry).

There is a DPC on the external walls, original by looks of it. I can't see a DPC on this internal wall, so I assume the bricks are soaking up ground water, hence this problem.

Ventilation is not great - I've just counted and there's only 4 air bricks round the whole house. But would this even help standing water?

My preferenced fix would be: Cut back the affected wood and attach new spans of wood (cutting back to the nearest subfloor wall for stability). Treat the new spans of wood with an anti-rot treatment, clean out the joist holes in the wall, and lay down some damp proof membrane in these holes.

Thanks guys for your help

 

[johnmichaels]

Just thinking about this some more - I hadn't considered the possibility that the joist doesn't end in this wall and maybe travel through the wall and out the other side, which would mean my proposed fix above wouldn't work. Is this likely, or would the other side of the wall start a new joist??

 

[skhudy]

Take a brick out next to the joist and check? Who knows what the builders did 60 years ago!

 

[ree]

Very doubtful that the joist runs on through the wall. To check, simply crawl around to the other side and look.

Its possible, that lacking a DPC, its rising damp but its irrelevant if you wrap the new joist tails in DPC material.

Its most important for the joisting to have lots of air bricks, and vents, supplying cross ventilation. Ventilation's effect on any standing water will be small.

"Honeycombed" is the term for half-bricked.