I went to an interesting job the other day, and found a situation I hadn’t come across before. Then, as often happens, I came across something very similar just a week or two later.

The original survey instructions for the first job were to look at one of the many mill conversions that have been carried out in this part of the world.  The problem wasn’t associated with the main conversion itself but related to a single-storey ‘lean-to’ annex adjoining the gable end of the original mill.  The developers had seen the opportunity this small(ish) building presented for another couple of units, and they’d created two flats, side by side.

For reasons I’m not quite sure about, running on top of the single-storey units, just above ceiling level were two, huge steel-beams; and as they didn’t possess much in the way of good looks, they’d been hidden by the simple expedient of placing false ceilings beneath them; thus they were in their own void, which had a head height varying between 600 and 900mm. The slope of the flat roof above occasioned the variation.

The owner of one of the units had complained that his ceiling was getting soaked when it rained*, and sure enough, when I went to see it, it had a water mark on the kitchen ceiling, running from front to back. At the time of my visit, the flat was empty and had been so for a few months; and the stains were obviously dry and had been so for some considerable time.

The developers had been in discussions with the installer of the flat roof, and he had been back on three previous occasions to check his work. Each time, he insisted there was nothing wrong but couldn’t suggest any alternatives. The developers were now coming under increasing pressure from the owner of the flat, and it’s safe to say that everyone believed the roof was faulty. Hence an independent opinion was now required, presumably to bash the roofer over the head with it.

Naturally, the first thing I did was to get out my ladder and climb onto the roof itself; and I have to say, it appeared to be in first class condition.  It consisted of a plywood decking with a covering of resin and fibreglass; and the detailing around the stanchions and other fittings was excellent; the fall was certainly adequate and the drainage and guttering were second to none. There were no obvious defects with the external coating and in short, I couldn’t see a single thing wrong with it.

Inside the building, in the entrance hall, a trap had been created so that access to the voids above the ceilings could be accessed.  It wasn’t really possible to do much in these voids because of the lack of headroom but it was possible to look around and make an assessment of what had been done.

On top of the standard plasterboards that constituted the ceiling, Rockwool insulation had been installed, and above ran the humungous girders I mentioned previously. They were in the region of eighteen-inches by nine- inches, which is quite a lot of steel in anybody’s book!

The short, upstanding walls around the perimeter had been lined with dense polystyrene insulation (Kingspan) and all looked well.  There were no indications of any leaks and none of the timbers I could access had a moisture content that would encourage rot.

Much head scratching here then!

I went back into the kitchen and re-examined the stains.  As I said, they ran from front to back and were quite pronounced. Whatever had caused them had certainly deposited a fair amount of water onto the ceiling above.  The kitchen was quite a way from the hallway and the relationship of items in the roof void to the layout in the kitchen wasn’t particularly obvious, at least it wasn’t to me. And it was quite some time before I realised that the stains were directly beneath the steel beams. Ah, an Edison moment!

Another quick look in the ceiling void, followed by a quick tour around the building revealed that the void was devoid (does that require a pun apology?) of any ventilation. Furthermore, so was the kitchen. It did have an extractor fan over the hob, but this only re-circulated the bacon-frying smells, it didn’t extract the air to the outside – not that these things (hoods) are ever any use anyway; but that’s another story.

So, it was now becoming obvious what had been happend.  All that nice, warm, moist air generated in the kitchen was wafting gently through the standard plasterboards – and by ‘standard’ I mean they didn’t have a vapour check built into them, i.e. foil backs – and into the cold, unventilated roof void.

This moist air was condensing on the massive steel beams, forming droplets, which were building up and then falling off, and soaking into the plasterboards beneath.

Recommendations? Ventilate the void; ventilate the kitchen; spray the beams with insulating foam. If condensation persists in this space, it will probably be necessary to overboard the ceilings (at least in the kitchen and bathroom) with foil-backed boards

Secondary recommendations: an apology to the roofer would be nice; and he can do my flat roof any time he likes (no, that’s not a euphemism)!

*this will have been coincidence, or more probably, association.  There may have been a surge in condensation due to high relative humidities during periods of rainfall, but this wasn’t the cause.

As I said, a couple of weeks later along comes a similar problem.  However, this time it involved concrete block and beams, not steel. The house itself, which was only two years old, was built into a banking at the side of the road; and a parking area, level with the road, had been created above a games room, which was adjacent to the house.  The parking area was asphalted and supported by the blocks and beams.

The ‘leak’ had originally been reported during the wet summer of 2007, and once again, the builder had been back several times, tearing his hair out and developing a certain ‘distance’ with the views of the owner.  Once again, ammunition, with which to administer a beating was required!

And once again, the [asphalt] covering was perfect.  The drainage was meticulous, and the cause was anything but obvious.  Fortunately, my steel beam episode was fresh in my mind, and upon examining the situation it was obvious that there was an un-insulated, un-vented void between the standard plasterboard ceiling and the concrete blocks and beams above.  To make matters worse, holes at the side of the room, which were also in the void, led directly to the ceiling above the bathroom – so lots of nice, fuggy air coming in from there then.

Recommendations: insert airbricks at ceiling void level; spray insulating foam over the entire underside of the ceiling.

Secondary recommendations: err… offer a big slice of humble pie to the builder.