Thread: gable end vent construction

Originally Posted by sfrew

g'day everybody,
I want to construct a slatted vent in a roof gable end.Thinking about it I can see lots of problems with angles inside the triangular frame of the vent as I want it to be rain proof the slats would be slopped downwards . Firstly I thought of making the trianglar frameand then marking the slat angles onto the frames. What do you think and is there a better way?
REgards Steve

If you make you frame you can mark onto the two down sloping sides of the triangle. The main thing is to overlap the slats so the wind can't easily blow rain through. To be effective they need to allow a fair bit of air flow - so the whole vent needs to be a good size and the slats not too thick and not too oblique an angle - I've used 45 degrees and that has worked well. best if they are higher up and under an eave.

Gable vents are one of the least effective ways of venting a roof unless they face prevailing winds and are placed in both ends of a gable roof. Even then the air movement rarely goes far into the roof. Effective ones are when the whole gable end is a vent - as in some older houses in the tropics.

Thanks Bloss
never thought about the slats over lapping to prevent water entry and yes there will be two one at each end and also slightly under the eaves
cheers Steve

Steve,
I would go for those whirley roof vents instead as they are more efficient. They will most likely save you money too. If you still go for the gable vents remember to install metal mesh to stop sparks and embers entering during bush fire days.
Regards

Originally Posted by orraloon

Steve,
I would go for those whirley roof vents instead as they are more efficient. They will most likely save you money too. If you still go for the gable vents remember to install metal mesh to stop sparks and embers entering during bush fire days.
Regards

Nope - Pretty inefficient actually, but probably marginally better than gable vents. The problem with the whirlybirds is that to be effective you need many more than the one or two that are installed usually and the intake vents in the eaves need to be matched for the airflow of the whirlybirds (if they are installed at all). Few sellers or installers will actually do the maths and advise you properly about how much airflow is needed (if they even know how) and what you need to install to achieve that. So most people are wasting their money.

Good advice on meshing if in a fire prone area - not an issue in a regular urban location.

I read up a bit on the air vents before I installed then many years ago and the bit most often missed is intake vents under the eves. The vents take hot air out at the top of the roof and cooler air enters at the lower vents creating a convection flow. Even without a wind blowing the heat in the roof space makes it work. This would also apply with gable vents too. The more vertical seperation you can get in the roof space between intake and exhaust the better it works. You are right about the suppliers not being a lot of help with info so I would say about 4 vents plus 4 in the eves for the average 3-4 br house.

Hey Sfrew,

How were you thinking about fixing the slats to the triangular frame? Are you going to butt them, or mitre them in, or other method of joining??
What dimensions were you planning on making them?

Also thinking about making a set of gable end vents myself. The angles inside the triangle are my problem as well. About a 2 metre basem, the pitch of the triangle has to be 22.5 degrees and the slats at 45 degrees, so trying to come up with an accurate method of rebating the slats into the frame is where I am stuck. Have you or anyone else got a possible solution?

Cheers
Neil

Hello Neil
Well I thought about it long and hard and came to the conclusion that I will make them out of steel .Why? for the same reason as you there is so many variables with wood with angles and such .It is too hard and I'm for ease of construction.What I plan is to make the triangle out of '' C" section and the slats out of tin plate shaped like the letter "Z" .
If you are interested Neil I will email a drawing to you
regards Steve

Just before you go ahead and start fabricating your gable end vents, do you know you can buy a variety of them prefab in plastic? Very popular up here in the tropics and haven't seen any failures yet from the copious UV light we have. They've been on the market for probably 20 years or so now. I have a joinery shop and wouldn't bother to make my own.

Mick

Steve, I'd be interested in seeing your drawings, but I'm not yet ready to conceed and go for anything but timber. I've seen them in plastic and metal, but I would sooner make it out of timber as it is a feature on the house being built.

Mick, the main problem with prefab plastic will be the dimensions. Base is 2 metres with a 22.5deg pitch. also has to be quite chunky to suit the design of the house. so if you were to make one from timber, how would you go about it??

I'm still thinking about the best method of construction using timber. Butting the slats against the frame, then gluing and screwing up from underneath to get a solid fixing would be the easiest way of joining them that I can come up with. I've thought about rebating them in, but I don't know of a tool that can accurately cut a 67.5deg rebate into the frame. A prototype done by hand ended up absolutely woeful.
Another idea I've had is to affix some small blocks onto the frame (Cut at the 67.5deg that I need and attached on the 45deg to suit the slats) just beneath the slats, then fix the slats to the blocks. Hopefully the blocks would be obscured by the slats or at least blend in.
Also thought of either biscuiting or dowelling the slats to the frame but not sure as to how accurate this would be either.

I'll try another prototype using blocks and butting and see if I can come up with something. Neil

Neil

To cut the rebates for the slats you could make a template from a piece of MDF with all the slats marked out on it at the correct angle and then router the rebates out using template guides on the router.

I didn't think you could get a router to 67.5deg. I only thought you could get like the tilt bases on trimmers which get you to 45deg??????

Originally Posted by Neil02f

.............I've seen them in plastic and metal, but I would sooner make it out of timber as it is a feature on the house being built......................

If you paint the vent you won't be able to tell whether it's made of plastic, steel or timber. If you clear finish it you'll need to be refinishing it every year to keep it looking good. Most people don't look much above head height so it's an awful lot of trouble to go to for a feature that most people will barely glance at, if they see it at all.

Mick