Extension Roof & Guttering Options

[Mag2.0]

Hi

Please see image attached.

Looking for some general discussion and recommendation on the roof type and gutter detail to a proposed rear extension.

The extension will be constructed tight up against a boundary. Nothing is constructed the other side of the boundary and we want all guttering etc to be on our land so not to upset the neighbours.

We are looking at going out a total of 4.4m maximum to the external brickwork.



Option 1.
Lean to type roof.
Allows the gutter to be placed on the rear of the extension.
The span is fairly large and outside the Trada timber tables. I however suspect a 47x 195 timber @ 400c/c would be able to span between support (subject to calculation).

We are limited to some existing windows at 1st floor level. We would need to go with a low pitch tile option (12.5%)
Assuming a 2575mm wall height to top of wall plate a 12.5% pitch looks achievable.
The bottom of cill is positioned at 3.8m above existing ground but have taken it as 3.6m to all for batten + tile + tolerance.

Is there anything that I should be aware of not covered in the above?



Option 2.
A flat roof.
I have always been wary of flat roofs based on problems experienced with older properties.
I would probably need to split the span of the roof joists into thirds with steel UB sections.

Pros:
Option to go with a nice lantern roof light.
No issue of roof pitch with existing window interface.

Cons:
Leaking issues
Additional cost of steel


Option 3.
Gable type roof with central ridge.
The guttering system would need to be internal to the roof, ie boxed.

What are the potential cons for this option?
Anyone with any experience with this system and pictures?

Looking at possible details on google, there looks to be a risk of water running into and out of the gutter as water can run off the roof at speed and there is no upstand to act as a barrier.

Obviously anything final would be subject to building regs check, open to general discussion / thoughts at this stage.

Regards

 

[Mr Chibs]

How come the guttering seems to be a big obstacle? Neighbour issues?

Think I would be favouring either lean to or pitched.

A mate has recently had a flat roofed installed, but could only manage just under 2.3m tall, feels a bit low for my liking.
Also had to have a lot of steel due to two lanterns.

 

[Mag2.0]

How come the guttering seems to be a big obstacle? Neighbour issues?

Think I would be favouring either lean to or pitched.

A mate has recently had a flat roofed installed, but could only manage just under 2.3m tall, feels a bit low for my liking.
Also had to have a lot of steel due to two lanterns.

No neighbour issues and we would like to keep it that way.
We wouldn't want the neighbours gutters over the boundary line so only right we apply the same rules back.

Was the 2.3m height a planning constraint?

 

[Mr Chibs]

Was the 2.3m height a planning constraint?

No, more a limitation of windows on current property.

Loftiness and light is what you want, feel a bit sorry for my mate, it's been an opportunity wasted.

I've been seeing more flat roofs being built and posi joists being used instead of wooden joists... wondered if these would help with your span.

 

[Mag2.0]

No, more a limitation of windows on current property.

Loftiness and light is what you want, feel a bit sorry for my mate, it's been an opportunity wasted.

I've been seeing more flat roofs being built and posi joists being used instead of wooden joists... wondered if these would help with your span.

I wouldn't have the same issue as the bottom of my window cills are 3.8m high, although im still dubious about flat roof and water ingress years down the line.

Ive also seen an increase of new developments using engineering floor joists. It removes the need for internal load bearing walls and allow for open plan living. Might give that a look into. It would help to avoid the additional cost of steels too.

Thanks Chibs!

 

[Mag2.0]

Does anyone have any experience of installing or having 'hidden' boxed gutters?


Regards

 

[noseall]

Does anyone have any experience of installing or having 'hidden' boxed gutters?


Regards

Horrific things. Avoid like the plague as no one seems to know how to weather them properly.

 

[noseall]

Hi

Please see image attached.

Looking for some general discussion and recommendation on the roof type and gutter detail to a proposed rear extension.

The extension will be constructed tight up against a boundary. Nothing is constructed the other side of the boundary and we want all guttering etc to be on our land so not to upset the neighbours.

We are looking at going out a total of 4.4m maximum to the external brickwork.



Option 1.
Lean to type roof.
Allows the gutter to be placed on the rear of the extension.
The span is fairly large and outside the Trada timber tables. I however suspect a 47x 195 timber @ 400c/c would be able to span between support (subject to calculation).

We are limited to some existing windows at 1st floor level. We would need to go with a low pitch tile option (12.5%)
Assuming a 2575mm wall height to top of wall plate a 12.5% pitch looks achievable.
The bottom of cill is positioned at 3.8m above existing ground but have taken it as 3.6m to all for batten + tile + tolerance.

Is there anything that I should be aware of not covered in the above?



Option 2.
A flat roof.
I have always been wary of flat roofs based on problems experienced with older properties.
I would probably need to split the span of the roof joists into thirds with steel UB sections.

Pros:
Option to go with a nice lantern roof light.
No issue of roof pitch with existing window interface.

Cons:
Leaking issues
Additional cost of steel


Option 3.
Gable type roof with central ridge.
The guttering system would need to be internal to the roof, ie boxed.

What are the potential cons for this option?
Anyone with any experience with this system and pictures?

Looking at possible details on google, there looks to be a risk of water running into and out of the gutter as water can run off the roof at speed and there is no upstand to act as a barrier.

Obviously anything final would be subject to building regs check, open to general discussion / thoughts at this stage.

Regards

Get a designer in - money well spent.

 

[noseall]

I wouldn't have the same issue as the bottom of my window cills are 3.8m high,

Cills?

Get someone to design your extension, rather than throwing random measurements about. 2575mm to the wall plate seems overly lofty. Window and door heads are generally set 2.1m. Sills are irrelevant and vary according to interior demands. You don't want to end up with an overly tall amount of masonry above the frames.

A lean-to roof will mean building a gable at each end - but will afford you a simple run-off for the gutter and means a single down pipe at the favourable end. It will also mean less overhang (50mm or so for the cloak etc) to deal with, as far as leaving room to avoid trespass.

 

[Mag2.0]

Cills?

Get someone to design your extension, rather than throwing random measurements about. 2575mm to the wall plate seems overly lofty. Window and door heads are generally set 2.1m. Sills are irrelevant and vary according to interior demands. You don't want to end up with an overly tall amount of masonry above the frames.

A lean-to roof will mean building a gable at each end - but will afford you a simple run-off for the gutter and means a single down pipe at the favourable end. It will also mean less overhang (50mm or so for the cloak etc) to deal with, as far as leaving room to avoid trespass.

t and vary according to interior demands. You don't want to end up with an overly tall amount of masonry above the frames.

A lean-to roof will mean building a gable at each end - but will afford you a simple run-off for the gutter and means a single down pipe at the favourable end. It will also mean less overhang (50mm or so for the cloak etc) to deal with, as far as leaving room to avoid trespass.

Hi Noseall.

Thanks for the reply.
Measurements are not random and are taken as surveyed against the existing property or proposed.
Point taken on the 2575mm. Existing internal ceiling heights are 2375mm. A 2.4m top of wall plate height from finished floor level would seem much more appropriate (2.55m from external ground level).

Dimensions to existing window cills are critical, otherwise the proposed lean to roof would have to be cut around the existing windows at first floor level. I would rather avoid this. I'd need to achieve a minimum roof pitch of 15 degree to avoid the use of expensive low pitch tile options. All this whilst trying to achieve the maximum extension depth. Otherwise i would have to move to a different roof type or reduce the extension size, so just trying to get to grips with my options before progressing any further.

PS, I'm looking at the options of designer input. I have an existing design and at this stage i'm looking at modifying that design to increase the depth of extension and the implications of this. Unfortunately the original designer is no longer operating.

Appreciate your input.

 

[noseall]

Dimensions to existing window cills are critical, otherwise the proposed lean to roof would have to be cut around the existing windows

Do you mean cills of heads?

 

[Mag2.0]

Do you mean cills of heads?

Window cills.
The window cills (bottom of window) at first floor level are 3.8m above existing ground level.

 

[noseall]

Window cills.
The window cills (bottom of window) at first floor level are 3.8m above existing ground level.

Ahh, gotcha.

 

[Mag2.0]

@noseall
No worries.

Looks like we will be going for a flat roof to gain the additional space.

Have flat roof coverings / construction come along in the last few years?
I have always been wary of them due to anecdotal evidence from friends of friends.

We would probably look at a warm roof built rather than cold roof.

Regards

 

[Mr Chibs]

Mate has just had a cold roof 'done' by the roofers. It's a rubber finish that looks very good, but the insulation is a mess, rushed IMO.
If it was mine I would have gone warm roof.