Windows without external sills

[newbuild]

I was wondering if anyone has experience of installing windows without using external sills? I am looking to install windows that are flush with the external brick wall. I understand the function of sills, but would be interested to know how others have removed them while maintaining water tightness. I am not looking to use a frameless system, but rather a standard aluminium window e.g. Schuco or Velfac. I've seen them on various buildings, and have attached a reference image of what I would like to achieve.

[markc]

A cill pushed water away from the wall and allows it to fall. Flush fit windows are simple to seal but the staining down the wall can be horrendous.

[newbuild]

Thanks for the reply - I hadn't considered staining. Do you think it would be an issue on mixed/multi stock?

[markc]

2 hours ago, newbuild said:

Thanks for the reply - I hadn't considered staining. Do you think it would be an issue on mixed/multi stock?

Difficult to say as it all depends on the amount of rain and airbourne dirt that will be washed down off the glass etc.

[Russell griffiths]

Where did you get that picture?

the problem with pictures is it doesn’t tell the full story, the picture might be nice but it could be horrible to live with. 

It doesn’t look like a robust solution, just a detail to come back and bite you down the line. 

 

I would want a small folded aluminium trim to cover the top of the brick, it might not need to project like a cill. 

 

Bricks are very porous.  

[A_L]

 @newbuild   I would want to see the jamb/sill/lintel details to mitigate thermal bridging by the bricks

[the_r_sole]

first question - why?

[Dudda]

Would you consider a brick cill? Similar to the below image I found on Google (ignore the head and style of the window, only looking at the cill).

 

[Mr Punter]

To be thermally efficient I understand that the glass units should be within the insulation zone, whereas if flush with the brickwork they will be in the cold zone.

 

I have done some a bit like this in Velfac but used a small cill projecting about 25mm:

 

[newbuild]

On 01/06/2021 at 12:39, markc said:

On 01/06/2021 at 12:53, Russell griffiths said:

Where did you get that picture?

the problem with pictures is it doesn’t tell the full story, the picture might be nice but it could be horrible to live with. 

It doesn’t look like a robust solution, just a detail to come back and bite you down the line. 

 

I would want a small folded aluminium trim to cover the top of the brick, it might not need to project like a cill. 

 

Bricks are very porous.  

I found the photo online. It's of a house built in south London.

Thank you for your advice, a small aluminium trim could well be a good compromise.

[newbuild]

On 01/06/2021 at 13:55, A_L said:

 @newbuild   I would want to see the jamb/sill/lintel details to mitigate thermal bridging by the bricks

I hadn't considered thermal bridging, thank you!

[newbuild]

On 01/06/2021 at 14:07, the_r_sole said:

first question - why?

I'm looking to achieve a minimalist aesthetic

[newbuild]

On 01/06/2021 at 15:08, Dudda said:

Would you consider a brick cill? Similar to the below image I found on Google (ignore the head and style of the window, only looking at the cill).

 

It's a nice idea, thank you. However, I'm wondering how practical it would be considering other comments regarding the porosity of brickwork

[newbuild]

On 01/06/2021 at 15:32, Mr Punter said:

To be thermally efficient I understand that the glass units should be within the insulation zone, whereas if flush with the brickwork they will be in the cold zone.

 

I have done some a bit like this in Velfac but used a small cill projecting about 25mm:

 

I'm not sure I understand why if the window is installed within the insulation zone it would be more thermally efficient - if anything I would imaging the reverse!

 

Thanks for the reference image. Yes, I think a 25mm sill would be more than acceptable.

[joe90]

I designed brick cills and windows completely in the insulation zone, I did seal the bricks with water proofer to mitigate porousity.

 

 

[A_L]

26 minutes ago, newbuild said:

I'm not sure I understand why if the window is installed within the insulation zone it would be more thermally efficient

 

Because it resists heat transfer from skipping around the frame in the bricks as I suggested earlier. 

[Bitpipe]

Another consideration is solar gain, the further recessed the window the more shading will be available.

[Carrerahill]

On 01/06/2021 at 10:11, newbuild said:

Thanks for the reply - I hadn't considered staining. Do you think it would be an issue on mixed/multi stock?

When I design/build things I always work on the principle of the hat with the big brim - get water away from the house, shed, garage, external power distribution cabinet with as big an overhang as I can. 

 

Remove the sill and you remove a layer of protection. 

[the_r_sole]

I honestly don't think it's an "aesthetic" choice that you should be making - windows in this country have cills for a reason, there's countless example of "minamilist" houses which still have some practical construction details, you'll likely find that you void any warranties for Windows or doors if you install them on the outer edge of the outer leaf.

The image in the op looks more like an unfinished central European building than a minamilist house, moving them to the outer edge is only going to make the weak points for water ingress weaker. Maybe the velfac could achieve the look as the outer glazing for them covers the frame but I don't think anyone would notice a practical window detail and a small cill...

 

[Faz]

The scheme next to mine installed the windows flush fit and they look shite - in keeping with the rest of his scheme tbh.

 

This photo may help (I took it mind to show how the sun and shadows highlight defects!) Look at the shadows.....

[Faz]

Oh - and he hasn't put on any external mastic either - a nice fun detail come winter.