Where does the membrane go..?

[ProDave]

Yes I admit the picture might be hard to understand.

Start with a sloping roof with your cross battens on to support the box profile. your bottom batten say 6" up from the bottom of the roof slope.

Now lay something down the roof to represent the box profile roofing.

Offer up your fascia board, with a vent strip on top of it and set it at a heght that almost touches the underside of the roof sheeting (small gap to allow for the infill piece)

Your fascia board will of course now be higher that the bottom of the slope. This is where the eaves tray comes in. The eaves tray fixes to the top of your fascia and creates the kick up slope to meet the main slope of the roof. This tray is made of plastic, and the joint between the fixing and the main part of the tray, is scored, so you can pre bend it to match the angle it has to be at.

Once you have done that mock up you take it all apart, lay the eaves tray first, then the membrane which now kicks up on the tray and over the edge. then fix the vent strip to also fix the bottom end of the membrane, then fix your battens and counter battens.

Making any sense yet?  If it wasn't hissing down I would go and try to get a better picture.

[Crofter]

Brilliant, that makes sense now. And also means that I need to fast-track the whole fascia bit.

I had assumed that, having got my sarking on, I could slap on the membrane and be wind/watertight for now, then sort out the eaves detail at a later date.

Third time lucky- what do you make of this interpretation?

[ProDave]

Yes that's about it.

What are you using to draw that sketch to do it so quickly?

TP sell those eaves trays dirt cheap if there is one near you? (don't think there is much "near" you)

[Crofter]

Sketchup. Would be lost without it.

I don't have a TP but there is a Jewsons and a Rembrand, I'd be surprised if I can't get the trays there. I was going to get them from Roofingsuperstore, which is where I sourced the membrane, but they were a bit silly on postage and anyway said the trays might not survive the trip.

 

Edit to add: I need a stopgap solution because I have to get watertight ASAP. I am nowhere near ready to fit fascia boards yet. So I think I will leave the membrane over-long and then temporarily tack it down with a bit of batten onto the rafter feet. That should do the job for now and when the time comes to fit the trays and fascia boards, I can just cut it back. I will have to watch I don't fix the battens too close to the edge as well, so that I can slip the tray under.

(I know fascias aren't exactly rocket science but there are some decisions on the exact measurements, which depend on some of the cladding details, and it's all stuff I need to kick into the long grass for now).

[ProDave]

I tried Sketchup, I just could not drive the damn thing. Nothing at all about it was the least bit intuitive and I just couldn't get it to do anything sensible. Perhaps I should try harder? Or I'm to old and set in my ways.

[Crofter]

I think I checked out a couple of beginner Youtube tutorials and then I was away. It has its problems, and it's not exactly pro software, but I found it far more intuitive than any of the actual CAD packages that I tried. It is worth checking to see if there is a shortcut for certain tasks, e.g. for an embarassingly long time I was unaware of how easy it was to copy and move elements around. Now I know that you can, for example, draw one joist and then just copy if fifty times and voila. I'm sure there are other shortcuts that I don't know about yet.

[Nickfromwales]

I'm with Dave. I just haven't tried any cad types of programs yet and really need to get fluent with at least one ASAP to start to design things a little more professionally than scribbling it down on A4 and taking a snap of it   

Luckily I have a 12 year old son who will no doubt tut and show me how it works. Once upon a time I was a computer savvy 12 year old, except it was on a BBC micro A upgrade ( the best of the BBC A AND BBC B I'll have you know ). Courtesy of my dad's DNA I grabbed a few spare 256 EPROMs out of knackered fruit machines ( from my uncle's company ) and was right at the forefront of cutting edge technology when I could store a whole game ( yes just one ) on my machine. Then came the DSDD disc drive ( an Opus Challenger 3 in 1 iirc ) which was THE daddy.

I missed out on the PC revolution in a big way so any tips on an idiots guide to cad would be gratefully appreciated. 

 

[ProDave]

When I tried Sketchup I just found I had no idea of scale, I didn't know if I was drawing a microdot, or something the size of the moon. And trying to draw two lines that touched but not overlapped seemed beyond the wit of man.

I use ORCAD, which is an electical circuit CAD program. I have been using it in one form or another for more than 20 years, originally runing under DOS and when it migrated to Windows kept pretty much the same look and feel.  I guess the difference is I know it inside out.  In my last job, just before I left, they switched to an electrical cad program based on an add on to autocad. I HATED it. Everything was so clumsy and imprecise, just moving a few wires around was a chore. And that's how I found Sketchup.

Orcad is pretty lousy for ordinary drawings, but at least I can do something in it very quickly.

[Crofter]

When drawing a line in Sketchup, you type in how long you want it, and bingo. You don't really draw freehand at all.

 

Anyway, I thought I had hijacked this thread quite enough as it was, I'd better be careful I don't get reported to a moderator...

[TerryE]

11 hours ago, Crofter said:

Third time lucky- what do you make of this interpretation?

Your sketch up pretty well matches my description of what we've done. We used some arras rail from the local timber yard for the 90/45/45 section. The membrane goes over this, and the ventilation strip is pinned to this and the tile /slate sits on top:

[Crofter]

So you've effectively got a solid fillet of timber to kick up the angle between the roof and the fascia?

 

For now, I'm just going to do a temporary tack down at the eaves, because I have loads of building materials arriving soon and need the roof to stop leaking!

[ProDave]

For a temporary fixing of the bottom of the membrane, don't nail it directly, fix it down with a batten nailed through and leave the nail heads a bit proud so you can pull them out.

[TerryE]

4 hours ago, Crofter said:

So you've effectively got a solid fillet of timber to kick up the angle between the roof and the fascia?

For now, I'm just going to do a temporary tack down at the eaves, because I have loads of building materials arriving soon and need the roof to stop leaking!

That's what we did.  For a couple of months the main waterproof layer was the membrane -- even though MBC wouldn't warrant this -- but we had absolutely no problems.  Then we lifted the stapling along the eaves edge and fitted the arras rail before the slater started work.  We also wrapped the front face and the underneath is a folded aluminium L section as I discussed recently in another topic.