Mansards with no soffit ovehangs

[jackcowdrey]

Hi all,

 

I'm just wondering how a mansard roof detail with no soffit overhangs and no parapets would work. Like the images attached. How are they vented? How is the gutter fixed? If someone could draw me a section to understand that would be great. Thanks.

 

[Mike]

At a guess they're not ventilated as they probably have very minimal insulation in the ceiling - there's not enough depth.

 

As for drainage, the roofs would likely slope backwards, so the rain would run back and down the mansard (unless driven by the rain).

[Gus Potter]

1 hour ago, jackcowdrey said:

I'm just wondering how a mansard roof detail with no soffit overhangs and no parapets would work.

1 hour ago, Mike said:

a guess they're not ventilated as they probably have very minimal insulation in the ceiling - there's not enough depth.

Great comment and input from jackcowdry and Mike. Old roofs were so draughty with traditional sarking / battens that the last thing on the builders mind was to introduce more ventilation.

 

Looking at these more modern photos I'm at a loss how they have ventilated it as the large format slates won't be helping as they are so tight. 

 

You could use traditional timber sarking with a 5.0mm gap between the boards and a breathable membrane (Tyvec Supro or similar)  but again these modern slates are so tight you need to be careful. 

 

Potentially you could get eaves ventilation (50mm air gap up the roof with minimum 25mm width soffit ventilation) up behind the gutter but there is no ventilation at the ridge.. unless it's all hidden on the back side? 

 

The potential for damp at the Juliet balcony looks high. A bit spoilt by the plastic soil vent pipe. A nice bit of cast iron

pipe would compliment.. if the budget stretched to that. 

 

As a rough guess it could work with a smaller slate size, a bit uneven with plenty air gaps between the slates.. but I can't promise at the moment! Food for thought though eh!

 

 

[saveasteading]

3 hours ago, jackcowdrey said:

is the gutter fixed? 

Brackets fixed to the rafters (probably the sides then a twist) or to the wall. 

[ProDave]

It could have been built as a proper warm roof design and would not need ventilation

[SteamyTea]

23 hours ago, ProDave said:

It could have been built as a proper warm roof design and would not need ventilation

That was my thinking.

By maybe we should say it could/should have been.

 

A warm room is just a tilted wall after all.