Aluminium Roofline - Help !

[Spinny]

Thanks to my builder problems I have now been through 2 winters without a finished roofline on the extension. Have had to make do with proplex which I have had to attach as a temporary cover.

 

The specification is for powder coated aluminium capping and fascia pieces as shown on the drawings attached.

 

However I am at a bit of a loss on how to interpret these drawings - where does one piece of aluminium profile stop and the next piece start ? - because clearly you can't fabricate or install in one piece for the overhang or one side wall. (One side is straight forward as it is just a capping piece). Can anyone make sense of the drawing in terms of how many pieces are envisaged and how they fit together ?

 

Also grateful if anyone can suggest or recommend suppliers that ideally can come to site to measure up, fabricate, and then install for me with secret fixings (rather than peppered with screwheads). I am Bristol area.

 

PS Also that piece above the bifolds at the bottom of the render board - are there edge pieces or render beads available for that ?

 

 

Edited March 22 by Spinny

[BotusBuild]

Three things that might help:

1. Some photos of what you have currently (the as built situation)

2. An index of what those numbers in the diagrams are (for example 8. Insulation)

3. An indication of precisely which pieces you are expecting to get fabricated

[Spinny]

The drawings show the edges and internal gutter detail of a warm roof. The green colour is PIR insulation which is covered with a single ply PVC membrane. The membrane runs out to the edge timber to provide the waterproof base of the edge gutters. A wide gutter in the overhang above the bifolds, and narrower at the sides of the building. The X's are timbers shown edge on.

 

I have used a red line to indicate the edge areas I am talking about. Labels 10 and 15 are the powder coated aluminium fascia/capping pieces on the overhang which run around the sides too.

 

I am wondering now whether the alu trim is supposed to lock together at the drip edge ?

[Russell griffiths]

Do you want to do this in aluminium, pvc plastic would be loads cheaper, will be easier to find a contractor to fit it, 

I would only go aluminium if this is a high standard finish you are after, there’s easily  a few grands worth of aluminium there once it’s powder coated to the colour you want. 

[Spinny]

Hi Russell,

Yes I definitely want to use aluminium as per the architects drawing. We have invested in alu doors and windows, cedral cladding, rooflights etc, we need to finish the job to the same high quality. It has been too painful a process to do otherwise.

 

 

[saveasteading]

I can have a think later but immediate comment is that the timber work is too approximate. Aluminum will follow the shapes and exaggerate them with the sheen . Will this straighten? Otherwise I think batten first.

will you accept visible screws?

 

 

[Eric]

  On 22/03/2025 at 15:53, Spinny said:

 

I can’t help with the flashings but it looks like the lintel over the window is on the flat rather than on edge (strength) and what is it resting on at the right hand side?

 

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[Russell griffiths]

If doing it in aluminium it will probably be made in three pieces starting at the bottom 

and angle going upwards finishing in the corner, then an angle that hat goes up but only 1/4 of the way, then an angle folded cap coming down to cover the last piece going upwards. 

[Mr Punter]

The top bit of flashing will hook over the timber and can be fixed underneath as far back as possible.  The lower piece wraps around the lower fascia.  You should be able to get this all fabricated off site.  God knows how to deal with the corners and abutments.  I suggest you get your architect to fit it!

[BotusBuild]

  On 23/03/2025 at 16:35, Mr Punter said:

I suggest you get your architect to fit it!

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🤣

 

The way i would do it - Minimum two pieces. Lower piece [fit first] goes on the lower horizontal, up the lower vertical, and along the midline horizontal. The second piece overlaps on the midline horizontal, goes up the upper vertical and then over the top.

[saveasteading]

  On 23/03/2025 at 16:35, Mr Punter said:

suggest you get your architect to fit it!

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Just providing a technical solution would be enough. They probably can't though because it is a specialist skill.

 

I've designed such flashings, hence my comments above. 

ie I'm saying don't use aluminium.

3 profiles is right. They are bent to order from a standard sheet colour, and then each of them is sliced to make into a corner, all by a specialist. 

Plus end details.

Then cut a hole for the spout and seal it somehow.

Anybody got any suggestions for invisible fixings?

 

I'd love it if I'm wrong and somebody knows a way.

 

You could think about one simpler flashing covering the large vertical, fixed on battens to remove the wobbles. Then paint or stain below. You still have the corners and ends to make and fix.

[Spinny]

  On 22/03/2025 at 19:48, saveasteading said:

I can have a think later but immediate comment is that the timber work is too approximate. Aluminum will follow the shapes and exaggerate them with the sheen . Will this straighten? Otherwise I think batten first.

will you accept visible screws?

 

 

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That corner pic shows by far the worst point, the timber lines are fine elsewhere. Pics were also some time ago before I made my own temporary covering with proplex. If it is still like that could be planed down I guess.

 

I guess there is a question about what thickness of aluminium should be used. Something thin is easily going to get distorted, but something thick should presumably stay straight and true. I found an old sample piece which is 2mm thick (a short bent piece albeit only a foot long) seems very rigid.

 

The front overhang above the bifolds is about 5m long - is anyone likely to do pieces that long ?

Don't want visible screws.

 

Could it not be done in 4 pieces as per my sketch attached with hidden fixings at the 'X's - basically interlocking at the drip edges ?

[saveasteading]

Useful pics.

Flashings are generally made in 3m lengths because the bending presses are made that size.

In 1mm metal they are usually overlapped and it shows.

In 2mm it can bd butted, with a back plate but needs pop rivets at the least.

2mm will be much the best for stiffness but is expensive and with limited colours.

Even that must be fitted without twisting or the sheen will exaggerate any change. 

That's a great drawing.  It seems optimistic to me, getting the u bends made with the right size of gap, then mastic to keep it tight.

I guess you could screw inside the gutter and at the soffit.

 

These bits don't travel well. Do you have a local fabricator? I used to have to drive about 30 miles to a cladding   merchant who served mainly the agriculture industry, then drive back very slowly with these on the roof, trying to bend.

If you can find one I would visit and get advice from the machine operator. They will know exactly what is possible.

I still recommend battens to square it all up and avoid contact with the main faces.