I forgot to mention last night, the chap I use for the SAP and the under floor calculations runs his business as a add on to his main job with his wife. His main job is a Building Inspector for a North London borough and the issue he did kick round his office pre the calculations. If any body wants to use him, please email me for detail.

Sounds like a major conflict of interests!

Are you serious?

Edit: Sorry ST, no mocking intended, I'm just laughing at the thought of them being transparent. Old cynic that I am.

But this is a perfect example of why BCO's should not be able to prepare material they themselves [or their colleagues] are going to vet. BS 13788 -2002
clearly identifies several 'important physical phenomena' not accounted for. See point [b] above. So either the Building Inspector doesn't know this, or he is ignoring it, or he is relaxing the Part C requirement. Whichever it is, those preparing such material should have no say in the application outcome.

It may even be illegal else it would not be a sackable offence.

Furthermore, as far as I know Building Control cannot be sued for damages resulting from Building requirement decisions [other than the obvious common law ones]

Very informative and, for us, relevant discussion as we are also considering exactly this for a bungalow with solid concrete walls and suspended floors, currently with a ventilated-to-exterior underfloor volume, with clean, apparently dry, concrete screed as base about 300 mm below joists. Pumping in EPS is attractive idea if you don't have to lift all the floor boards to install a vapour barrier that might well be imperfectly fitted and easily damaged.

In the above posts, with EPS bead filled, now non-ventilated, sub-floor space, surely there is an increased risk of condensation, particularly at the exterior wall, because the EPS is internally insulating this wall so it is colder and this cold surface will give an ideal surface for condensation as a result of moist warm internal air reaching the cold area. So then perhaps you could get mould and spores coming back into the house migrating through the bead.

johnuready, do your engineer's calcs take the edge condition into account? Or are the calcs just for the general ground area of the space? In the other thread VH says monitoring says it all is dry in actual installed situations so maybe all is okay. EWI would surely help situation by helping to keep the wall warm.

Has anyone done the THERM and wufi modelling on the edge condition?

BS EN ISO 13788 does not take account of the 'important physical phenomena' present in such structures as this [See my post above]

EN 15026 has a wider scope of assessmnet. See http://www.wufi.de/index_e.html but even wufi is one dimensional. It doesn't seem to be able to model the edge condition sugested by Paul in Dublin. I guess thats why he suggested combining it with THERM? Is that right Paul?

Edit: You have to click on the EN 15026 tab on the above link

Here it is removed

Another area where there is a joist adjacent to a wall. Note the proximity to a vent. Though there are no vents at the opposite end of the floor. So no through ventilation

So how does anyone considering filling ther floor void with polystyrene beads know whether any of these horrors exist in their floors?

And have you considered the consequential effect of raising the temperature of any such timber containing wet rot?

Yep, I agree and that's really the point - there are lots of them around. And how do you know whether the one you are going to infil is one of them without invasive examination?

Even if you do examine them, can you really predict with certainty what will happen when you raise the temperature of a damp/wet timber bearer against a cold wall. Or one on a cold damp stub supporting wall. The theory says there is greater a risk of condensation - the timber gets warmer and the masonry gets colder. If you get the right moisture content in the timber then the floor could be riddled with dry rot in no time.

Hi Tom, I'm not sure what you mean. Are you saying that the timber needs to fall below the dewpoint for rot to occur? Because it's not just about condensation, there are other causes of moisture build up in floors, and these can be interdependent.

The conditions needed for dry rot are at least 25 % moisture content and a temperature above 16 degrees. http://www.waltersforensic.com/articles/civil_engineering/vol1-no9.htm What invariably stops this from happening in timber floors is ventilation. This was insufficient in my pics above

I don't see how you can say this cannot happen where a floor void is filled. Specifically the two locations I mentioned above : Wall plates on stub and external walls; and where a joist is adjact to a wall.

and where do empty fag packets end up on building sites??

Yes! but Mike George's photos mostly show joist end rot which seems to indicate that the wall is damp, if it was rot due to condensation on the joists then shouldn't the rot be on the bottom of the joists where the condensation occured?

Posted By: fostertomI'm thinking of a 70s rendered cav wall bungalow with voids, which we're EWIing and airtighting. Think I can guarantee that dry even without disturbing carpeted and kitchen-fitted floors for inspection, let alone u'floor insulation access. In that case, instead of the 'EWI down to found' approach, we'll just take it down to GL, at least on the sides where it stands well above GL, and fill the u'floor voids with Leca. Maybe some 'wing' Leca round the other 2 sides.

How are you planning on installing that Tom?

Posted By: Viking HouseYes! but Mike George's photos mostly show joist end rot which seems to indicate that the wall is damp, if it was rot due to condensation on the joists then shouldn't the rot be on the bottom of the joists where the condensation occured?

Hi Viking. Yes I agree that the wall is damp. That's part of my opposition to this approach. How can you know whether the existing floor has wet rot in joist ends and/or bearers without invasive investigation, which I'm presuming you don't do?

Also there is evidence of condensation, the rot is where you would expect for this to be the case. ie, where the timber is closest to the cold masonry, both on the underside of the joists, and on the ends adjacent to the masonry.

Here's a picture of the underlay I took up showing evidence of mould

Posted By: Mike Georgethe linked ones I found were only for solid floors

True

Posted By: Mike Georgeand not pumped in

Definitely pumped in - that's the key. I'll try to find sources if time allows (too busy on forums!)