Exceeded maximum gauge on roof battens .....

[F20C]

Afternoon all,

First post here ..... hopefully someone can offer some advice please.

We're having a 2 storey extension built where the brickwork is flush with the back of the existing house, and the brickwork on the front of the house is stepped in around 5' on the second storey to give some relief (so the front of the house didn't just look like a big slab of bricks).

The joists and rafters have gone in, however the rafters on the front of the roof are approx 16" longer than those on the back.

When the roofers have put the battens up, I was told that the maximum gauge between them should be 100mm. Where they've had to try and keep the tiles consistent around the full roof, the batten spacing has had to increase up to 115mm in some cases on the front.

My question is, what is the danger of exceeding the maximum recommended gauge? Is there a higher risk of rain getting in? Is it potentially a slight cosmetic issue or should I be more worried about safety concerns? Or (ideally) is it nothing to worry about at all?

I don't want to upset my builder unnecessarily, so was hoping for a bit of advice first.

Thanks for reading

C

 

[vinn]

OP,
Will you post a pic of the build so far?

edit:
I've just read the post below and revised my opinion of what the OP might be describing. An unequal pitched roof?

What tile is being used?

 

[datarebal]

I take it it is a hipped roof with plain tiles & bonnet hips? and valleys?
What is the pitch of the roof?
A bit naughty tbh unless its a very steep pitch there is a chance of the batten getting damp but unlikely to pour in.
They should have adjusted the gauge the other way round. by closing the one side down but keeping the other at the max gauge .
Having said that, 16" is a fair bit to lose. What is the rafter length

Gauge is measured top of batten to top of batten

If there are no hips or valleys then there is no reason to tweak anything

 

[F20C]

Exactly right. An unequal pitched roof (much more simply put than i said it!) with plain tiles and bonnet hips. I presume it will have a valley on the front where it ties into the existing roof. I'm not sure of the actual rafter length or roof pitch I'm afraid.

Trying to upload a couple of pics of the roof before the battens went on so you can see how it ties in. Hopefully this works ...

 

[vinn]

OP,
Thanks for the prompt pics.
Can you be more exact as to what tiles you have - there are various gauges for various plain tiles by various Mfr's - eg. Marley Concrete plain tile or Rosemary plain clay tile etc.

I'm assuming that all the common rafters on one plane of the roof are the same length.
And all the common rafters on the other side of the roof are all 16" longer.

FWIW:
From what I can see in the pics, and allowing for an angled ground view, your rafter framing should work out with a few jiggles.

There are different ways of doing irregular pitched roofs but where you are intersecting with another pitched roof it narrows the options.

 

[datarebal]

you are governed by the existing roof in this case.
The bonnets need to course round. so is the existing gauge 115mm or 100mm (I expect 4 inches)
are the ridge heights the same?
Pitch looks about 35 degree ..

 

[F20C]

Thanks for the feedback - I'm not sure of the exact tile type, they're 1950's if that helps narrow it down at all?

The roofer himself told me it should be 4" max, but said he might need to go to 4.25" which is "OK". I went up the ladder after they left for a nose and the bottom battens I could reach to measure were 4.5" apart.

A couple more piccies which might help:

 

[F20C]

@datarebal - Good question. I didn't think to measure the existing battens whilst i was up there. The ridge height will be the same.

 

[datarebal]

its a standard plain tile, max gauge is the same. if its the same as the garage then its a concrete plain tile

the vally could have been lead or grp then it would not have needed to course, making the hips easier.

 

[F20C]

OK. The guys were keen to tie it in with tile to make it look cleaner.

So, how worried should I be (if at all) about the width between the battens? I'm sure the roofers won't want to re-do it and will play it down if I ask them directly.

 

[datarebal]

width between battens? have you measured top of batten to top of batten??
The pitch of the roof looks about 35, This is the minimum recommended pitch for plain tiles.
The max gauge appears exceeded.
If you had an issue the manufacturers will walk away.
Your guys certainly won't want to rebatten, that would mean new underlay too..
4.25 battens will likely get wet. 4.5 be worried..
talk to your builder.

 

[F20C]

Yuck! OK. Appreciate your thoughts thanks.

One last question. Is there a building standard that dictates how many consecutive batten joints can be on the same rafter, or is it more of a guideline? It appears you shouldn't have more than 3 consecutive in a run of 12 battens? What is the reason for this?

I may have a few consecutive joints of 5 or 6

edit: to clarify - top of batten to top of batten (not inbetween) is 4.5" in some places

 

[F20C]

Update - found the angle of the pitch on the drawings. 40° on the back and 35° on the front

 

[datarebal]

Should have lost the valley.

The new underlay would have been better under the old at that point too.
Tricky but good practice

whats done is done

 

[noseall]

Agree with Data. If the pitches differ then the gauge will also differ due to the longer rafter length etc. They should have forgotten about the valley tiles and had a dry valley, giving a definitive break and set out an independent gauge.
4.5" is wrong.