New flat roof - water pooling - is it normal?

stuart45

A flat roofs should be set at a minimum of 1:40. This allows for bits of the roof where the timbers dip and everywhere is at least 1:80. 

Bendy_House

stuart45 said:

A flat roofs should be set at a minimum of 1:40. This allows for bits of the roof where the timbers dip and everywhere is at least 1:80. 

So, a 2" slope would suggest this roof should be less than 7' long?

OP? How long is yer 'oof?

plumb1_2

I would suspect it might have something to do with the extreme hot weather we’ve been having?

Plus it depends on how the felt has been applied hot pitch or cold system.
It needs ripping off and replacing. I would presume the roof structure was installed by the builder and not the roofer
If you intend to say in the house long term I would opt for a epdm type roof covering.
Many years ago I went on a training course to install Trocal roofing system, really good product 

stuart45

Bendy_House said:

stuart45 said:

A flat roofs should be set at a minimum of 1:40. This allows for bits of the roof where the timbers dip and everywhere is at least 1:80. 

So, a 2" slope would suggest this roof should be less than 7' long?

OP? How long is yer 'oof?

That's correct. The longer the joists and firring pieces, the more chance there is for dips. When you eye up modern timber joists you can see the problem. Ideally the joists or rafters should be curved up so they will straighten up with any weight on top.

user1168934

Bendy_House said:

stuart45 said:

A flat roofs should be set at a minimum of 1:40. This allows for bits of the roof where the timbers dip and everywhere is at least 1:80. 

So, a 2" slope would suggest this roof should be less than 7' long?

OP? How long is yer 'oof?

It's 3m long.

Dimensions are 3m x 2.1m

TELLIT01

stuart45 said:

Bendy_House said:

stuart45 said:

A flat roofs should be set at a minimum of 1:40. This allows for bits of the roof where the timbers dip and everywhere is at least 1:80. 

So, a 2" slope would suggest this roof should be less than 7' long?

OP? How long is yer 'oof?

That's correct. The longer the joists and firring pieces, the more chance there is for dips. When you eye up modern timber joists you can see the problem. Ideally the joists or rafters should be curved up so they will straighten up with any weight on top.

Really? I would expect the timbers to be strong enough to support the weight of the roof construction without flexing down.  The fall should also be such that water doesn't pool on it.  Either way, the builder needs to come back and provide a permanent fix.

stuart45

TELLIT01 said:

stuart45 said:

Bendy_House said:

stuart45 said:

A flat roofs should be set at a minimum of 1:40. This allows for bits of the roof where the timbers dip and everywhere is at least 1:80. 

So, a 2" slope would suggest this roof should be less than 7' long?

OP? How long is yer 'oof?

That's correct. The longer the joists and firring pieces, the more chance there is for dips. When you eye up modern timber joists you can see the problem. Ideally the joists or rafters should be curved up so they will straighten up with any weight on top.

Really? I would expect the timbers to be strong enough to support the weight of the roof construction without flexing down.  The fall should also be such that water doesn't pool on it.  Either way, the builder needs to come back and provide a permanent fix.

It's the same with a cut roof, the rafters should be done in the same way.
If all the joists are perfectly straight there's no issue. If there's a curve in them, as there often is nowadays, it's better that the curve goes the same way, rather than having one up and the next one down. If they all go the same way it's much easier to slate or deck out.
If you are going to put them the same way, you may as well have them arched up, as they are more likely to go down than up. With roofs you have to consider any imposed loads like snow.
It's not a massive issue, but it's just as easy to put them the right way up.
Crowning your lumber – Greenwood Construction General Contractor

macman

plumb1_2 said:

I would suspect it might have something to do with the extreme hot weather we’ve been having?

Plus it depends on how the felt has been applied hot pitch or cold system.
It needs ripping off and replacing. I would presume the roof structure was installed by the builder and not the roofer
If you intend to say in the house long term I would opt for a epdm type roof covering.
Many years ago I went on a training course to install Trocal roofing system, really good product 

It's the same contractor. 

youth_leader

I do feel for you, after spending so much money on it. 

I bought this bungalow in March 2021 and was really pleased the flat roof had been replaced in 2019.  I wasn't so pleased when it was blown off in Storm Arwen, and the lounge/kitchen ceiling came in too.  It was a resin roof,  and the builder said it was a cowboy job as the roofer had only nailed  to the joists, instead of screwing it down.  I had to fight for the insurance to pay, eventually settled at £13,500.  

I hope you can get it fixed. 

[Deleted User]

Is there a reason you went with felt and not rubber or fibre glass? 
I needed my roof doing and struggled to find a felt contractor. Went with fibre glass in the end.

That aside, yours doesn't look a very professional job. The seams round the edges appear to be lifted and the whole lot hasn't be laid properly.