Mould or something horrible under floorboard

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I should leave your tiled vestibule where it is unless the floor seems soggy or bouncy under the weight of two people.

The first two new pics show:

possibly fungal infected joists at the extreme left and right.
The plates acting as a sleeper wall appears to be packed off the earth on timber.

All joists, flooring, packings and debris in the bay area should be disposed of.

All the rubble and debris at the front wall to be cleared out - in fact, wherever you encounter rubble or cellulose debris dispose of it.

The new vents should be located in the unobstructed joist bays.

The hearth pic:

the "flooring" appears to have been an off-cut of a flat pack panel or similar - resting on odds and ends.
The hearth appears fungal free and dry.
All wood debris should be removed.
All wood work/joists trimming the hearth should be isolated from masonry or earth contact.
At some future date, given that the hearth is redundant, it would pay to totally remove it and any brick fender wall, and joist and board across - this would give better underfloor ventilation.

By and large, things are looking much brighter esp at that rear wall. I'm glad for you both.
Take pics of everything, not for here but for your future reference.
 
as soon as i saw the 1st pic,you can tell theres been problems there before,
and as you say the builders havnt found anything else then at least you can breather just a tad now.
 
Sounds like none of your experts has a clue!
Looking at your pics it looks like the underfloor cavity is full of rubble dirt. Usually the cavity should be at least a foot or more to be effective. Air cannot circulate if it is full of rubble, remove it and ensure there is good flow under the whole void through your airbricks. Its a dirty job but you can do it yourself and it wont cost a penny. Choose a builder next time who gets rid of his rubble and doesnt sweep it under the floorboards.
 
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A further update....

In addition to the three damp and timber companies that have visited (details in previous post), we've had four more:

(4) Kenwoods. Said it was definitely dry rot. Thought the white whispy growth was salts. He was scaremongering... got to do it right, get a guarantee, otherwise it will just come back etc etc. He said he would half the living room area and the corridor. Haven't received quote yet.

(5) Timberwise. He said it was definitely Mine Rot (Fibroporia Vaillantii). Their report says:

Some flooring had been lifted to reveal a localised infection of mine rot (Fibroporia vaillantii), affecting the floor, joists and bearer plates. The probable cause for the infection is a lack of subfloor ventilation and timbers being in direct contact with damp sub-floor brickwork; the over site has no suitable isolation of timbers from brickwork.
The remaining floor area has the same problem (no isolation of timber bearer plates where brick piers are situated). The clients own builder should lower over site where feasible and install a suitable felt damp proof membrane. The fire place hearth also has built in timbers around and inside the damp affected hearth; client should remove or again isolate these timbers from masonry or brickwork.
Timberwise propose to remove excess over site to the front section of the front room where our works are to be carried out; remove loose brick piers and affected flooring, joists and bearer plates. New two course brick piers will be installed as necessary and dependent on site conditions will be cemented into place. The over site will be treated with a suitable fungicidal solution and newly treated flooring, joists and bearer plates installed, isolating from the brickwork with a suitable damp proof membrane.
Client should increase sub-floor ventilation by installing 1 new 225mm x 150mm air vent to the left hand side of the bay and a periscopic vent to right side of the bay as indicated on the sketch plan.

They've quoted:
Brick piers as specified £376.73 + vat
Spray treatment £207.54 + vat
Timber renewal £779.05 + vat
Removal of rubbish £209.58 + vat

(6) Rentokill. Wet rot. No need for chemicals. Just remove affected timbers, make sure wood is isolated from brickwork with damp proof membrane. (not trying to sell us anything hooray!)

(7) Peter Cox. Said he can’t properly diagnose it as the area has been tampered with (new skirtings added, floorboards been up a week etc). Said thinks it’s more likely wet rot than dry. Said (with an air of 'why am i wasting my time with you') we look like DIYers so just buy the chemicals and spray ourselves. They’d charge £400-500 just to spray.

Sooo 7 opinions in and the counts are:
Wet rot: 3
Dry rot: 2
Mine fungus: 2

What confusion!

Only 1 of the 7 thought the white whispy growth was dry rot, the rest thought it was more likely to be salts/resin from the new plaster. Also our friend checked the floorboards in room above and they were dry and fungus free. So we're going to hedge our bets here and not remove plaster. Also we made bigger holes in the chimeny breasts for vents and stuck our hands in - seems free of rubble downstairs and you can feel airflow in the upstairs room.

So for the floor area, the consensus seems to be remove the timber in affected area, clear the rubble and add more sub-floor ventilation. We are already over budget and want to do this as cheaply as possible, so we will use our builders who are still on site to do the work replacing timbers. The question is whether to treat with fungacide or not. A friend of a friend advised us to buy the wood treatment for £18 from Toolstation (protects from wet and dry rot and wood boring insects apparently) and paint the the timber ourselves. Can anyone advise on the effectiveness of this or whether we should fork out for a company to do it?

Another question I have relates to the issue of 'isolating' the sub-floor timber from the bricks, which a few people have recommended. From what I understand this means adding some kind of damp proof membrane between the bricks that lie underneath the wooden beam that supports the joists (sorry I don't know the correct terminology). Is that right? And does this need to be done throughout the whole room? I can see how this can be done in the area where we're replacing the timber anyway but not sure how we'd get the membrane in place in the rest of the room where we're not replacing anything. Any clarification appreciated!
 
Hi yes!
We still haven't made final decision re what to do. And waiting for quote from our builders.
Further advice and response to questions would be appreciated :)
 
In an early post you mentioned "black spot or condensation round the chimney breast". I didnt see any black spot, only the fluffy stuff and smears of plaster (skim?). Do you think that the reception room lacked ventilation, and heavy condensation was present?

Your sub-floor ventilation should flow freely thro from the front elevation to the rear elevation.

How many air bricks are now installed in the front elev? And the rear elev?

Any more info ref. why you have the sloping floors?

The flues need sweeping. None of your flues are connected.

Earlier the builder was a "shoddy builder", now you are waiting for "a quote from our builders". What is the builder quoting for?

You can spray or brush on some chemicals. All the rotted wood should be gone. Joists will rest on DPC's and be capped at bearings.

All wood must be isolated from contact with ground or brickwork.

Membranes to be laid where accessible or possible.
 
Charlottemclaughlin,

Further answers and advice was provided - now i'm just wondering what happened next?

AAMOI: there are quite a large number of DIY'ers following this thread and it would surely help them to be also informed how the story ended - or not?
 
Many thanks to everyone that gave advice on this problem. In the end we got our builders who were already on site to remove the rotten floorboards and sections of the joists. We cleared out the rubble and they put in new joist sections, and took floorboards from upstairs to replace the ones that were removed. We bought cuprinol 5* wood timber treatment from amazon and a garden sprayer and sprayed the wood. I bought some damp proof membrane and tried to explain that we needed to isolate the wood from the brickwork but I'm not sure they understood or did this correctly. We couldn't afford a D&T specialist to do the work and so we did the best we could with the resources we had. Only time will tell if the mould returns.... Fingers crossed
 

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