Hidden Eaves Design Detail

[Jeffers_S13]

I'm rebuilding an outbuilding and I'm up to wall plate height.

I've built it with cavity wall, block inner skin and brick facing.

The old buildings on my place all have hidden eaves and they're all 9" solid brick walls with dentil course and sailing course at the top. The bottom row of tiles are bedded at an angle onto the outer face bricks and the upper end of the tile hooked over the batten.

On my rebuild surely I need to allow some ventilation and the tiles shouldn't be bedded onto the outer facing brick? or should they?

Does anyone have any details or photos of how to design/build a hidden eaves arrangement?

 

[Jeffers_S13]

 

[Jeffers_S13]

This is what I have built, it has 100mm cavity and concrete block inner skin. I want to copy the appearance of the adjoining building.

 

[gonch69]

We normally fit an over fascia vent to top brickwork an tiles don't need too be bedded if fixed to battern

 

[^woody^]

If you fit a suitable breathable membrane then you don't need to ventilate the roof

 

[noseall]

If you fit a suitable breathable membrane then you don't need to ventilate the roof

You would think so, wouldn't you. I'm of the opinion that there are no breathable membranes (on their own) that can deal with extremes of cold UK weather coupled with a vapour rich interior. We always mechanically vent because of this.

 

[^woody^]

You would think so, wouldn't you. I'm of the opinion that there are no breathable membranes (on their own) that can deal with extremes of cold UK weather coupled with a vapour rich interior. We always mechanically vent because of this.

There are BBA approved membranes that need no venting. Presumably they have been performance tested to get the certification.

 

[Jeffers_S13]

Thanks for the replies. I found a similar thread on this:

https://www.diynot.com/diy/threads/roof-eaves-design-detail.359695/

I tried to contact noseall to see if he has any pics or to see how he did it (assuming he built it) but I dont seem to be able (or can't work out) how start a conversation with him, it just says I'm not allowed.

I found a few products that sort of fit what I'm looking for I think, this one is my favourite. I will have to chase out some of the mortar in my perps and re-point to fasten it in (assuming the tabs match up with my oddly shaped/sized bricks). I will also need to fit a comb somewhere somehow, probs onto the rafters a bit further up than ideal?? as I'm using Marley Mendips.

 

[Jeffers_S13]

I just realised noseall was one of the respondees ! do you have any pics of that one you posted a pic of in 2013?

 

[Jeffers_S13]

We normally fit an over fascia vent to top brickwork an tiles don't need too be bedded if fixed to battern

Hi gonch, thanks for replying, do you have any part built pics for me to study please?

 

[noseall]

There are BBA approved membranes that need no venting. Presumably they have been performance tested to get the certification.

I get that. I helped out a BCO when investigating some Tyvek problems*. You could see the water beading on the underside of the felt and the obvious drip line where it accumulated.

I agree that conditions have to be to the extreme and properties and their moisture content are idiosyncratic, but I like the belt and braces approach and have always supplemented breather membrane with vents. And why not. It's what air gaps were invented for.

*It was resolved with an air tight loft hatch.

 

[noseall]

Hi gonch, thanks for replying, do you have any part built pics for me to study please?

This is what an OFV looks like fitted on top of a fascia....

Bolt3_LI

• noseall
• 27 Apr 2022

Bolt2_LI

• noseall
• 27 Apr 2022

 

[Jeffers_S13]

Now found this, I think this is my preferred choice.

https://jjroofingsupplies.co.uk/klober-vented-eaves-protector-3-in-1-combination

Can just fix to rafters, no fixings onto corbelling, so if first row of tiles nailed down and their weight will hold it all in place?

 

[Jeffers_S13]

This is what an OFV looks like fitted on top of a fascia....

Bolt3_LI

• noseall
• 27 Apr 2022

Bolt2_LI

• noseall
• 27 Apr 2022

Thanks noseall, I dont have a fascia unfortunately. Having one would fix a lot of my concerns very quickly! and gives me heaps of options for ventilation.

My next concern is getting the right angle on the last tile. My trusses are going to need to be made to just the right size to match up with the width of the building and my choice of eaves vent

 

[noseall]

Thanks noseall, I dont have a fascia unfortunately. Having one would fix a lot of my concerns very quickly! and gives me heaps of options for ventilation.

My next concern is getting the right angle on the last tile. My trusses are going to need to be made to just the right size to match up with the width of the building and my choice of eaves vent

If your trusses don't provide you with the correct detail at the eaves, you can always correct thing with some clever use of eaves sprockets, although it is better to get it right with the trusses (if possible).