Mr Roofer

Back to work with a bang this week. A lot of technical enquiries and unusual applications for spray foam polyurethane.

One enquiry was about an extension to house in the planning phase where the roof was going to double up as a roof terrace, slabbed over and used as the patio above the single storey extension. I presume they would also have a staircase leading up to the patio. Their dilemma was to achieve a 0.2 U value for the flat roof come ceiling as they were going to build a reinforced concrete slab over the extension so that the terrace would be on top. Compounded with this was the fact that headroom in the new extension would be tight. One problem I pointed out was that the construction was due to take place after April 2006 when the building regulations change and will require even lower U values to be achieved then. U values measures the heat lost through a building material or composite material, measured in watts per square metre at one degree Centigrade (technically Kelvin) temperature gradient difference between ‘inner’ and ‘outer’ sides of the constructed ‘material’. I believe the U value come April will require 0.16 meaning that typical industrial spray applied polyurethane depths to achieve this will be 120 mm plus and given the variation in spray depth 140 mm nominal may have to be specified to ensure a minimum 120 mm is actually coated. The proposed solution called for 300 mm of mineral above a ceiling board held up by 100*50 mm joists with a 50 mm continuous ventilation gap above the mineral wool to avoid condensation with ample air bricks either side to provide the continuous ventilation. No wonder head room was an issue, with the mineral wool solution losing a best part of a foot and half in height!

Another enquiry was about a steel tower. They had already had the tower fabricated to put onto the supporting brickwork and it was going to be bolted down. All well and good but what about the U value and condensation control I asked. Simple solution really, spray foam polyurethane solves both problems by being heat welded direct to the steel, with no air gap behind the polyurethane as it is bonded direct to the steel so there is not a condensation issue on the steel tower itself and the depth of foam governs the U value achieved to meet the U value specified. And we can retro fit the polyurethane foam and spray in situ. Another problem solved for a customer who thought he would have to send the tower to us for spraying or find some system to double skin the tower and provide ventilation to the upper skin to avoid condensation.

On another note a surveyor called from a very well respected firm to pick my brains as he put it. No problem fire away. It was quickly evident that he was not aware of the forthcoming April changes in the building regulations. Now if these professional firms cannot keep up with the changes what chance has the small jobbing builder? April 2006 will prove to be an interesting month and it will be interesting to see how local authority building control inspectors educate and help their ‘clients’ understand and apply the regulations or just refuse to pass new build that does not meet the new building regulations. In my experience, I have both met types, the really helpful building control inspector who goes out of his/her way to help, offers advice and comes up with solutions (though not officially ‘allowed’!) and the obstructive jobs worth. Hopefully it will be the former. There is clearly a need within the construction industry for this sort of information to reach the people that need to know; a simple way would be for the government to post update booklets on mass to every single building merchants in the country, after all, there cannot be any builder who does not have to go to a builders’ merchant? But no, this will not happen. Ironic that these services (government) are paid for by taxes but the service back is non existent. The suits create their towers on our backs, the overalls do the work and take the wrath of offficialdom for being ignorant. That’s my rant for today!