I can't comment on the ply prices because you don't say which type it is.... If you can't join two sheets on a rafter each time (PS drill and screw, don't nail) so that the next join is on a rafter as well, then stick intermediate rafters in........or if easier, stick cross noggings in between the rafters so you can at least get the sheet edge to fix to something (note the join will show from underneath). Onduline is pretty damn good stuff.......make sure you get the eaves closure fillers as well. If you are going to use Onduline; if it were me, I would still use ply on the roof and lay a moisture barrier under the Onduline, if anything just so it looks OK from underneath...... You will probably still have to cross nogging the rafters to take the Onduline; although considering the weight, intermediate rafters would be better.
I called the suppliers and its "ordinary sheathing/shuttering ply". Noggings are a good idea. Like that. I don't care what it looks like as long as it is dry. If Onduline comes in at £250 with a 15 year guarantee that makes more sense to me than £150 on felt that never seems to last more than 5 years or me. Will I get away with 12mm ply with Onduline? It only way 6.4kg per sheet which seems quite light, that's only about 70kg per side of the roof. I know the boards will be much heavier.
I don't know how Onduline will perform if it is on an uninsulated roof, although I suspect condensation will form on the underside...........it's called the dew point (IIRC) where water vapour from inside hits a colder surface. Without insulation there isn't much you can do to stop it from happening (use of material wise), but it shouldn't be as bad as steel / aluminum, so you don't really need the plywood in that case, although the ply would provide strength and bracing to the roof so it couldn't twist an collapse under wind load etc. However, my roof decking is 9mm ply with Tyvek (moisture barrier/breather membrane....there are cheaper alternatives) over the top, then battens and fake slate.................There is no sign of condensation on the underside of the ply after 9 years. If you are going to use Onduline, I think 12mm should OK, but try not to stand in the middle between the rafters.....I reckon you could get away with 9mm because the Onduline won't be supported on it. Actually, I just had another look at your photos..........your roof structure is of proper trusses, so I would image they were designed to take quite a load........I can't comment if the spacing at 675mm or so is part of the design, but the norm is 600mm, so they aren't far out.
OK, so something like this ON the ply but UNDER the Onduline should reduce condensation? YBS Roofers Choice ROOFERS 003 Light Breathable Membrane Grey 1mm x 50mm | Roof Insulation | Screwfix.com I have a roofer coming tomorrow for a quote so I can get a benchmark and see what he suggests.
I'm hoping they take quite a load as I'm intending on hoisting my bike up on them to drop front wheel/forks out.
I doubt the trusses have been designed to take a bike. There are designed safety margins, one wheel off might be ok. The truss fixings look light, these add to the truss strength. I don't think you will have the end bearing for such an imposed load. Additional bracing, studs etc will help spread the load.
You could consider this if the money is available..... Airtec Double Insulation 1.05 x 25m | Roof Insulation | Screwfix.com or this by the looks of it, which is pretty cheap IMO. Breathable Membrane Roofing 1Mtrx50Mtr Roll - Permavent | eBay Research before you rush into buying..... You need something to keep water out, but remember, if it lets vapour out, it will condensate underneath the Onduline, so in that case, don't close the eaves profile of the Onduline completely because it will need to ventilate. IIRC, Onduline do a ventilated ridge and eaves fillers.
Far too heavy across that span in itself, I reckon.....and something like a scaffold pole would bend and the ends would pull off the walls..............if you fixed the ends to the wall, it would pull the walls in, probably ripping the wall plate (the bit the trusses bear on) off the truss ends........Whoops, one roof on the floor. What you could try is bolting some larger timber joists (say, 8" x 2") to the sides of three or four trusses, then run a scaffold pole or summink across all four at right angles. If you look closely at the open structure of mine, you can see the rafters are heftier and closer together than yours, plus you can also see a beam I made up......... ....but then I don't lift my bike on the roof structure.............I use a home made stand (£10)
The trusses are bearing on the partition head, not a wallplate. regardless, it looks to small a member. The floor may not have the capacity to take the load at that point. What's the span from each end of the truss.
The trusses are bearing on the partition head, not a wallplate. regardless, it looks to small a member. The floor may not have the capacity to take the load at that point. What's the span from each end of the truss.
Head plate, wall plate; whatever you want to call it..... I bet you are going to tell me that the bottom of the partition is the partition bottom and not a sole plate...... It depends if you have worked on timber frame buildings dating from c1300, which is where many of the modern terms originate. The head plate doesn't look too small, it is too small.
There you go............just right for wasps to build nests if there aren't insect guard fillers for the profile closures.
Wasps nests I can live with. The wife is hypersensitive to their stings and runs a mile when she sees them. A nice wasp nest or 2 will guarantee me peace and quiet.
