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Housing - New Build: Splayed window/door reveals

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    • CommentAuthorwookey
    • CommentTimeMay 28th 2011 edited
     
    I saw pics of window reveals that are angled so as to let more light in here:
    http://www.cropthornehouse.co.uk/10-05-30_glazing_over/11.jpg

    This seems like a good idea, but I wonder exactly how the detail is put together. Attaching the windows solidly to square boxing is fairly easy. If it meets the window frame at an angle at the front edge, what is the window attached to?

    I also need to fit a door, where it would be good to angle the reveal so that the door opens further out of the way, and we get a bit more light in, but a door has to be attached nice and solidly to survive a lot of opening and closing over the years. How do you make it strong enough without compromising thermal and airtightness considerations? In theory one could attach the doors to the outer leaf with stainless brackets for strength and just have the angled reveal butting up aginst the frame, but I can't see how to actually screw the brackets to the frame as one can't get at the place you need to screw.

    The drawing below uses brackets screwed into frame and then into the boxing material. Would that be solid enough or would the boxing material just flex? How thick a bit of ply or OSB would be needed to make this rigid and provide sufficient purchase for the bracket screws? 12mm? 15? The ply is frame-fixed into the block at the chamfer.

    Any better ideas?
      angled_reveal.png
    • CommentAuthortony
    • CommentTimeMay 28th 2011
     
    I had several splayed window reveals, I had window frame mounted behind the outer brick skin, fixed a continuous batten up the frame 12mm proud and fixed my reveal material (pb) to that

    I also had some sheet insulation behind my frame to mitigate thermal bridging
    • CommentAuthorpmagowan
    • CommentTimeMay 28th 2011
     
    Can you not take the ply reveal to the outside edge of the doorframe leaving a triangle to fill with squirty foam? I have found squirty foam to be plenty strong enough in the past. You could make a fairing block if concerned.
    Paddy
    • CommentAuthorwookey
    • CommentTimeMay 28th 2011 edited
     
    You mean like this?

    My builder likes the ply going all the way across like this as it makes it strong (braced against outer leaf), but this does leave you relying heavily on the foam, whic I agree can be very strong in a gap between frame and masonry, but I'm not sure it's sufficient in this sort of wedge-shaped arrangement, and it's hard to get any back-up fixings in.

    And this isn't thermally as good, although it probably isn't terrible either.
      angled_reveal2.png
    • CommentAuthorwookey
    • CommentTimeMay 28th 2011 edited
     
    Tony, if you've only got PB on the inside, and the frame is inboard of the outer leaf - what's actually holding it up? Brackets/batten on the outside leaf?
    • CommentAuthorpmagowan
    • CommentTimeMay 28th 2011
     
    Yes, That is pretty much what I had in mind. If you are pernickety about the small thermal bridge then this can be removed by stopping the ply on the inside block a little short. You then have a space running parallel to the ply that needs to be filled in order to come up to the inside of the door frame (essentially so you cover up the 'gun foam'). This could be filled with EPS or ply backed insulating material (if you are not plastering internally).
    Don't know if t hat makes sense but it would probably be more thermally efficient than your original drawing.

    I suppose a lot of this depends on how much faith you have in the strength of insulation and squirty foam. I think both are strong enough in practice (in the odd DIY job we call it structural foam!). For my plans (which are the same as yours apart from the outer skin of brick, i.e EWI) I was thinking of first laying down an EPS board then the ply, attaching the frame with foam, and then overlapping with more EPS. I will probably play around with it to work out how strong it is and the best arrangement.

    Paddy
    • CommentAuthortony
    • CommentTimeMay 28th 2011
     
    I overlapped my frames behind the bricks by 30 to 40mm and fixed diagonally through them or with brackets to the bricks, the heavier windows were supported on steel dowels supported in the brickwork

    I think the first style of drawing has less thermal bridging than todays one.
    • CommentAuthorchuckey
    • CommentTimeMay 30th 2011
     
    Nay lads!, you've got it all wrong. Turn your outside masonry inwards and put a vertical DPC in some where, then as a good measure drill plug and screw some steel straps across the angled face. This way you only have to buy 8 screws and plugs and use 4' of banding for a window reveal.
    Err, thats how they do it around here and I can recommend it for growing mildew in the corners of the window reveals. Builders ha! :-(
    Frank
    • CommentAuthorwookey
    • CommentTimeSep 9th 2011
     
    OK, this is actually due to happen next week (windows finally turning up). I've done a new drawing whcih I think will work. Fortunately the door is opening inwards so any slamming doors will be pushing out against the outer leaf brickwork, not trying to crack the doorframe inwards out of the reveal, so I reckon brackets aginst that leaf is all that's needed for a good solid fixing. Everything else is a matter of making it airtight on the inside, windtight on the outside and minimising thermal bridging.

    Ideally we'd have a design where the reveals could be installed before the doors/windows (so the whole frame was ready for fixing the doors/windows into), but I've failed to think of one - because you need access to fix the brackets to the outer leaf, so the side reveals have to go in last.

    Latest drawing here:
    http://wookware.org/extension/builders/pdf-drawings/details/angled_reveal.pdf

    So the procedure is:

    * Before fitting, work out door bottom height and fit support brackets, cut angles in blockwork and fit threshold plate.

    * For frames, stainless/galv brackets to outside leaf is main support - screw to frame, then position frame, then fix to wall. (slotted brackets may be helpful here).

    * Before fitting frame put tape round outside attaching 15cm strip of plastic. Fold in gusset at corners to expand into angled reveal. Add inner brackets on top of tape (for doorway, not necessary on window). Stagger outer and inner brackets.

    * Once frame is in place cut side ply (12mm?) to leave 8mm gap to frame (for foaming). Fix batten on back for bracket screws. Apply orcon bead, then screw in place into block and then screw brackets from door through into batten. Fill behind frame with foam to make windtight and solid.

    * Silicone gap outside. Tescon Tape plastic sheet to ply (covering brackets). Contega tape on inner corner.

    * Tape reveal to threshold and head boxing pieces.

    Bit fiddly and as I'm no longer DIYing (windows too heavy to move!) fiddly costs me money. So improvements are welcome.
    • CommentAuthortony
    • CommentTimeSep 9th 2011
     
    I fitted my frames slightly behind the brick reveal (40mm) and securely fixed to the bricks with angle brackets too.

    But broadly similar (I didnt use any ply or osb) and no problems.
    • CommentAuthorwookey
    • CommentTimeSep 9th 2011
     
    Did you put angle brackets beneath as well as at the sides? I've effectively only got one 'side' to fix to due to the corner in the middle, so can't rely on just holding up both sides. What did you weatherproof the 40mm external gap with?
    •  
      CommentAuthorfostertom
    • CommentTimeSep 9th 2011
     
    Make a splayed groove into the inside face of the window frame, just like a Velux, and fix the outboard edge of the plasterboard into that, fix its inner edge to the inner skin, no need for framing or anything in between.
    • CommentAuthortony
    • CommentTimeSep 9th 2011
     
    I sat my windows on metal dowels to take the weight at the ends and wide ones got a bracket in the centre at the bottom too.
    • CommentAuthorMikeRumney
    • CommentTimeSep 10th 2011
     
    Posted By: fostertomMake a splayed groove into the inside face of the window frame, just like a Velux, and fix the outboard edge of the plasterboard into that, fix its inner edge to the inner skin, no need for framing or anything in between.


    ... yes and then the insulation can be brought to infront of / inboard of the frame, reducing frame surface available for bridging ...
    • CommentAuthorwookey
    • CommentTimeSep 10th 2011
     
    Yes. I think you are (all) right. I originally came to this planning on the ply-box support arrangement, before realising that it wasn't going to work. I was stuck on that and failed to realise the box is unnecessary for airtightness and plasterboard support. PUR will do for that.

    I do see an ordering issue though. You need access to fix the bracket tothe wall (or the window) so can't fit the PUR until after the windows are in. With a 78mm window in a 200mm cavity It may be tricky to do well (and not leave gaps for wind blowing in cavity. It's OK at the splayed reveals, but harder to do under and above the window.
    •  
      CommentAuthorrichy
    • CommentTimeSep 12th 2011
     
    Seems overly complicated and involves beveling blockwork and insulation. I don't like seeing osb touching the outer skin and the whole thing will get messy if the guys fitting it aren't working to engineers tolerances.

    I'd build a jig that can router a groove for a 12mm ply panel at an angle in the frame.
    Sit the frame behind the outer skin, rebating frame or blockwork/stone if the window has to be nearer the outer face.
    Step blockwork and insulation.
    Use a 100 x50 timber fillet to form angle screwed to blockwork, ply screwed to that holding frame against reveal, a variation of how the Victorians did it, they used propeller plugs cut off at the right angle.

    Personally I would glue the ply into the groove with PU glue.

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