monopitch with furrings ?

[barneybodge]

Hi all,

Im about to build a flat monopitch roof for a garden building using full length corrugated sheets.

I have ordered some furrings (spelling ?) which consist of 4x2 cut down from 4" to zero and will be using them to give a minimal pitch and allow me to have a non sloping ceiling inside.

The surface will be decked with grade 5 moisture resistant t&g and the corrugated sheets fixed on top.

The building is 7.5 mtrs long and 3.6 mtrs deep and I know someones going to say " A 4" pitch is not even 5 deg mate", but I cannot stand the site of giant wedge shaped hats on buildings and a 4" pitch is all I can bear to look at. As long as I take measures to prevent capillary action im happy to use a lower pitch.

What im unsure of is whether these furrings need to be mounted on to 4x2 sitting on a wall plate or maybe 3x2 or even 2x2 ? The less height of timber above wall level the better !

Hope that makes sense

 

[Jasonb]

Assuming your fall is along the 3.6m width and your joists run the same way, just nail them to the top of each joist, then board along the 7.2m length.

Jason

 

[barneybodge]

Cheers Jason,

The fall is along the 3.6 width and the joists / wallplate are not on yet. Im just a little concerned about the 8" + height of timber at the front, which will require a really deep fascia.

I assume I will need 4x2 joists regardless, otherwise the 'zero' end of the furring will have no strength underneath it. I may decide to notch the joists and bring them inside a bit on wall hangers, and not bother with a wall plate after all.

Timber yard are charging me 91pence per metre for the furrings, seems reasonable to me.

Cheers

 

[masona]

I have ordered some furrings (spelling ?) which consist of 4x2 cut down from 4" to zero and will be using them to give a minimal pitch and allow me to have a non sloping ceiling inside.

Firrings cuts are made out of 2"x2" and not 4"x2"!

The building is 7.5 mtrs long and 3.6 mtrs deep

6"x2" is okay for what you want with the 2"x2" firrings on top.

A drawing would help.

 

[barneybodge]

Too late to change the firrings, already paid for and just been collected. £23.00 all in, which I think is an excellent price.

Looks like they will have to go on top of 6x2 in order to support the weight of 18mm t&g inside and out.

Thanks for your help.

 

[masona]

Oh well you won't get any puddle up there then

I'm thinking it will be a bit awkward fixing the 4" firrings at the deep end.

If you wanted to, you could easily run a circ-saw or saw bench to trim it down and the waste off-cut can be use for something.

 

[barneybodge]

Fixing them at the 4" end was one of my concerns too, maybe I will fix all the way along until near the thick end and screw some plates on the side.

I would have preferred a lower 2" firring like you said, but im always concerned about capillary action.

http://www.roofhelper.com/typesofroofs.htm bottom right picture is exactly what it will look like, except not at that pitch

I start tomorrow and no doubt it will chuck it down all day.

Cheers

 

[Jasonb]

Just use a 12mm flat bit to drill 60mm into the firing, then 6mm through the rest of the way. The 12mm hole will take the screw head and screwdriver bit no problem then you can use something like 80mm screws which are a lot cheaper than 6" ones.

Jason