JohnMarsden

Hi all, I’m at the boarding stage of our loft conversion and have - with the cold weather recently - noticed that early in the morning there are a small amount of water droplets coming from between the Velux frame and opening on 1 of our 3 windows. Originally thought it was a leak so pulled out my frame and reveals insulation and ripped out a bit of expanding foam I’d put between the gaps and have gradually discovered that it’s condensation forming on the underside of the cladding of the window itself. From daily observations it’s dried up by about 10AM. At the moment the loft is a bit of a Swiss cheese - there are large eaves storage areas that have yet to have doors (insulated) put on them etc or be boarded, and so theres a few avenues warm air could get up into the rafters and condense on the underside of the cladding, but would the ventilation gap (50mm - I’ve 150mm rafters with 100mm PIR between them followed by 70mm PIR below rafters on the pitch) not have been sufficient to remove this moisture? I am trying to figure out if that once this is all sealed, boarded and plastered it will resolve itself and this is understandable at this stage of the build given that so much air can freely circulate up to the roof space, or if something more drastic is required. The windows have thermal collars fitted as standard. I have ordered a few Velux BBX vapour barriers for the windows in the hope this will address something, but would be grateful for any input. I had considered stripping off the insulation from the other 2 windows but am wondering whether this would actually aid warm air finding the cladding and lead me down the garden path.

Thanks! For anyone in the same position, the legislation is here: It is also reflected in the fire regs - essentially, the definition of what constitutes an "external wall" is quite clear now. cheers

Slate tiles

Hi - I haven't found this answer searching the forums and I'm therefore wondering if it's a stupid question. We are having a loft conversion done. Part of the new roof is mansard. Does the mansard wall count as a wall or a roof for insulation purposes? Edit: I should say, the loft conversion has mansard 'walls' leading up to a flat roof.

Thanks for your response Mark - my thoughts. I previously did this on the ridge beam only but never a floor. These photos are the best I have at the moment - they show the three beams and most of the splices. There are additional beams at the back that have the same splice connections too but they are in two sections rather than three. The same problem with them too though - not as to spec by the structural.

Hi there, We are currently having guys install the steels for our loft conversion. On the couple of floor beams that have gone in so far, I have seen these splices (there are three beams, with two splices in each - i.e. each beam is in three sections). Structural engineer had specified no more than one splice per beam, and a top/bottom plate to be bolted at each join. Builder has not done this and seems to have used end plates on RSJs so top and bottom plates could not be added to be flush even if desired now. Builder is saying it’s fine we do it all the time and their “internal” structural engineer will be fine and BCO will sign it off. Our structural engineer is not happy and says he will not stand behind it. Any thoughts/comments/advice? Is there even a chance that these connections are sufficient? The purlins are already being supported (temporarily) off these steels and subfloor that’s already partially down so redoing the 3 that have gone in so far is going to be a lot of work and backtracking but if that’s what needs to happen it needs to happen.