Creasing Tile Sill (Cill)

[MortarThePoint]

The build is coming at pace so I'm definitely in avalanche mode now.

 

We liked the sills on the example house at the NSBRC (photo below) so have decided to go that way. The closest thing we have to a detail from the Architect on this is shown in a cross-section (extract below). Does anyone have a better detail for a creasing tile sill?

 

I am presuming (danger) that the tiles just sit on the brickwork and there is no damp feature or anything beneath. Thinking about it the low angle mortar joints will get a lot of rain on, so is there supposed to be DPC underneath?

 

I've come across the 'cill tile creasing brick' below which I think looks like a good option. The brickie warned that creasing tiles always get smashed on site once fitted so these could help reduce that as well as being easier to fit. Has anyone used these?

 

The last thought is that I didn't specify that the sill will end at the edge of the brickwork reveal rather than being slightly wider, so the brickie has made the sill ~45mm wider than the reveal. I think I prefer how the photo below looks, but does anyone have a concern either way.

 

[ProDave]

The cill tile has a drip groove in the bottom which must be set forward of the wall.

 

The picture, made from plain tiles does not have that drip groove detail so water may track back into the brickwork.

[markc]

Apart from the missing drip groove, the tiles in the photo are correctly fitted with staggered gaps to prevent (or at least make it extremely difficult) water getting down in the joints between.

The cill bricks rely on the mortar joint remaining intact otherwise water is allowed to enter.

[Temp]

39 minutes ago, ProDave said:

The cill tile has a drip groove in the bottom which must be set forward of the wall.

 

The picture, made from plain tiles does not have that drip groove detail so water may track back into the brickwork.

 

+1

 

If plain tiles are used the bottom layer must also slope down..

 

https://chandlermaterials.co.uk/media/wysiwyg/Creasing-Tiles-Leaflet.pdf

 

 

Edited August 27, 2020 by Temp

[MortarThePoint]

15 minutes ago, Temp said:

If plain tiles are used the bottom layer must also slope down..

https://chandlermaterials.co.uk/media/wysiwyg/Creasing-Tiles-Leaflet.pdf

 

Thank you for the link and image. Interesting cavity closure, but the important detail shown is the DPC.

 

Do you think a DPC is a must or as can we trust the staggered joints to be waterproof enough?

[Temp]

That drawing shows a block laid horizontally on the inner leaf. You wouldn't do that in practice as it bridges the cavity, instead there would possibly be an insulated cavity closure all around the window. In which case I don't see why a DPC is needed.

Edited August 27, 2020 by Temp

[MortarThePoint]

I can't find any guidance that says the sill has to be wider than the opening. The closest I can get is NHBC guidance 6.11.7 to do with Render:

 

 

We will have some rendered parts on the upstairs.I think the thing being avoided is water going off the side of the sill rather than flowing to the front.

 

By implication, this suggests the sills don't have to be wider than the window reveal.

Edited August 28, 2020 by MortarThePoint

[MortarThePoint]

Fitting windows now. The tile cill is to go in after (recommended by Brockie) Wondering what is going to support the window at the bottom though as the cavity closer is only supported by the inner leaf. Packers between the frame and cavity closer would be normal I guess but the cavity closer isn't fully supported.

[MortarThePoint]

Here are some photos to help see the issue.

The first is only 620mm wide so not much of an issue. Being a lighter window and not much distance to the Cavalok cavity closer's corner it won't twist much. Packers at the bottom near the corners and packers + fixing lugs at the sides, job done.

 

The second photo is more of an issue, 1800mm wide. Cavity closer isn't so stiff against twist at the centre is far from corners. Packers at the bottom near the middle will twist the closer outwards.

 

Solutions I've thought of so far:

1. Put temporary blocks (wood) under cavity closer to support against twist until creasing tiles added later
2. Screw top of window frame to underside of steel lintel. This would provide vertical support, but put the frame in tension not the normal compression. I would need self tapping pan head screws long enough to go through the frame and at least 15mm further (5mm gap + 10mm into lintel). Probably means a 70mm screw which difficult to get so may end up as "woodscrews".
3. Imagining that a approx. 75mm high galvanised L bracket exists that I can put a few in. The vertical part would screw to the fat part of the cavity closer and the horizontal part would screw to the top of the bricks. Google waits.

I don't think it's an option to just support the bottom in the corners as the window will then sag in the middle. Longest window I have to solve this for is about 2.5m wide.

 

 

[MortarThePoint]

I think I have a candidate for option 3:

   https://www.toolstation.com/corner-brace/p43669?utm_medium=feed

Put in at ~300mm centres they would provide vertical support to the cavity closer. These windows are about 10kg per 300mm so that's quite a load. The inner leaf would take about half that, so each of these would need to be holding up 5kg through a single screw hole (lower one will be below cavity closer).

 

More expensive alternative that my not be quite high enough but has more holes:

   https://www.toolstation.com/galvanised-angle-plate/p98602

 

 

Edited August 12, 2021 by MortarThePoint

[MortarThePoint]

This is getting annoying complicated now. The technical guy from Cavalok is on holiday, but I suspect he'll just say that the cavity closer has to be supported by a brick.

 

Below is the original plan with the frame shown against the cavity closer, though in reality there will be a packed out 5mm gap there. The front face of the window is 54mm behind the face of brickwork. The point of support of the window frame will be the two barbed sections along the interior face of the window (circled in smaller extract below).

 

An option that comes to mind is to use a piston brick to support the cavity closer. This would require the window to move outward and the tile angle to be steepened. It could perhaps be cut from a standard pistol brick or be fully custom. A benefit is it throws in an alternative to the batten that is usually used to get the tile angle. It places the second frame ridge (as you head from the interior) above the brick so Cavalok will probably prefer this. I have shown the arrangement with a standard pistol brick below in ORANGE. If we angled the cut on the standard pistol brick slightly it would make room for the window to move back about 10mm.

 

I have spoken to a brick fabricator and to cut a pistol normally costs £1 each, but with the additional cut it would be more like £1.30.

 

 

 

Pistol Brick:

[Brickie]

Can you not affix the cavity closer to the frame somehow,so it’s not dependent on some form of support?

[MortarThePoint]

3 minutes ago, Brickie said:

Can you not affix the cavity closer to the frame somehow,so it’s not dependent on some form of support?

 

But the cavity closer needs to support the frame. Would be easy if I was just trying to hold the closer itself up. Or do you think the frame would be self supporting enough from the side mountings?

[MortarThePoint]

Well I'm no expert, but I am improving. Here's my fourth cill. My first three were in a group done together and smudged a bit unfortunately. Should have waited longer with those before jointing up.

 

 

[Mr Punter]

I am no expert either but that looks a very decent job.  I imagine the others can be cleaned up with a bit of acid but be careful of the window frames.