Garden Room with No Roof Overhang - How to Vent Cladding?

[the_kilo_1984]

Hello folks,

I'm waiting on the delivery of my SIPS garden room kit (4.8m x 3.6m), with my foundation and sub-frame now complete.

I'm looking into cladding details and we are keen for a contemporary style with no roof overhang around the building, and the cladding running to the top of the walls on all 4 sides. I've added some photos to give an idea of what we're after.


We will be wrapping the sips panels in tyvek breather membrane and adding vertical and then horizontal battens to form an air gap before fixing the vertical timber cladding.

My question is, what is the best way to vent the air gap at the top, considering we will have no overhang?

1. Is the EPDM roof covering that I'm using breathable, and will therefore let moisture escape? If so do I just lap it over the cladding at the top and fix my facia board?

2. Is my only option to run a horizontal wooden trim across the top of the cladding at the top to form a pathway for the moist air, as per photo 2?

3. Do I need to lap the EPDM over the cladding and then drill vent holes in the cladding near the top (not preferred)

4. Anything else I've not considered?

I've been searching the web for a definitive answer to this but I'm struggling to find anything. All comments or suggestions (or criticism!) welcome in my search for something I can build that works.

Many thanks.

 

[mrrusty]

EPDM is not breathable! I would plan for a small overhang 20mm ish - and use a perforated trim for a narrow soffit vent. In any case, when it's p******g down you will wish you had a decent overhang.......

 

[freddiemercurystwin]

A garden room can still look contemporary even enhanced further with a normal or a larger overhang. It's all in the design.

 

[the_kilo_1984]

Thanks for your comments. You made a comment about wanting a good overhang when it's raining hard - is this to protect me from the rain or to protect the cladding? If it's the former then I won't be using it in bad weather so that's not too much of a concern. If it's the latter, won't the overhand only protect the top 1/4 of the cladding from rainfall? The rest will still get wet, regardless of the overhang?

I do like your suggestion of a narrow overhang though, I've convinced the Mrs to go up to 75mm for it as long as it looks slim. Cheers

 

[the_kilo_1984]

A garden room can still look contemporary even enhanced further with a normal or a larger overhang. It's all in the design.

Very good point, and we have seen some garden rooms with overhangs that we like. I guess we were trying to make it as sleek as possible, but if it needs a small overhang then so be it. Thanks

 

[mrrusty]

is this to protect me from the rain or to protect the cladding?

Bit of both really, with no overhang, the door and window sealing gets tested more against leaks, when you open the door and it is raining, the weather comes in easier risking the floor getting wetter, and the cladding is exposed to more dripping. It's a choice, but for our climate, I prefer decent overhangs.

 

[^woody^]

They always look cool in the brochures, but a roof projection does a very important job in protecting cladding. The designer or supplier won't tell you this, and you only get to see it a few years later.

This is what normally happens. It can be variations of the theme - either damp staining, bleaching or algae patches, but the principle is the same whenever rainwater is allowed to run down cladding and is not cast off via a roof or cill projection