How to determine pitch of my extension

[JKami84]

I don't know how the builder is adamant this is 17+ degrees. I have been outside and asked several times and he is confident it is made slightly above 17 degrees. 

I have used my own online resources and doing it based on counting bricks from the outer wall to the existing house wall. 

Simply put, for my 3400mm length extension, it requires a rise of 1030mm ish (so just over 1m) . 

So counting brick courses - i'd say that is 14 brick courses. 

I only count 12 brick courses. even looks like just 10 courses from the photo ,but he showed the outer wall is 2 bricks lower when looking it directly from the back. 

How is he still so adament its 17 degrees? no more bricks need to go against the existing house side. 

[Redbeard]

I suggest you put your values into something like this https://www.calculator.net/right-triangle-calculator.html?av=&alphav=17&alphaunit=d&bv=3400&betav=&betaunit=d&cv=&hv=&areav=&perimeterv=&x=Calculate and ask how he gets something different. Or buy him one of these (I have no connection with this supplier) https://www.ebay.co.uk/itm/286798055236?campid=5338947458&mkevt=1&mkcid=1&toolid=10050&customid=&mkrid=710-53481-19255-0&loc_physical_ms=41684&loc_interest_ms=&campid=5338947458&mkevt=1&mkcid=1&toolid=10050&customid=519bad6e777c152ae5f5c591c56048c7&mkrid=710-53481-19255-0&loc_physical_ms=41684&loc_interest_ms=&msclkid=519bad6e777c152ae5f5c591c56048c7  and then get him to tell you where the wall-plate has to go. It's worth noting that if your tiles are for min 17 deg pitch then a bit more gives you 'weasel room'.

[JKami84]

Yes, I've used those tools to know the difference between existing house wall and top of the end of the extension should rise about 1040mm. 

 

BUT i'm no builder. Maybe you its not just the brickwork that determines the pitch?? he has left now. he has assured me 3 times today that its over 17 degrees. he has been spot on with a lot of other things - so i have some trust in him. but i also trust triganometry. 

 

minimum i wanted was 15 degrees, and he said he has kept it at 17 degrees for it to be safer. so he knows exactly what he was trying to achieve. 

 

he said he used an app on his iphone. 

[Gone West]

14 hours ago, JKami84 said:

minimum i wanted was 15 degrees

Just counting the bricks in the picture I make it around 12 to 13 degrees. The easiest way to show him would be to put a digital spirit level on the string line.

[JKami84]

45 minutes ago, Gone West said:

Just counting the bricks in the picture I make it around 12 to 13 degrees. The easiest way to show him would be to put a digital spirit level on the string line.

ok - so update. it is actually 13 bricks high. from the outside photo is is deceiving because when you look at it from inside it goes lower than the bricks we having been counting to. OK - 13 x 75mm per course = 975. 975mm against a 3400mm run is 16 degrees. I also used my tape measure and got 980mm. 

 

However, maybe i am all muddled up in this - Where does the wall plate go? If the wall Plate sits higher than the highest brick, that would add marginal steepness . especially if on the outer side the birdsmouth in rafter keeps it the same steepness. 

but if the wall plate sits just under the bricks - then that will reduce it from 16 degrees. 

 

Either way currently the brickwork rise is about 60mm short of 17 degrees.