Semi extension roof

[chopkins13]

Hi all,

Our house is a 1950's linked semi, a house attached on one side, on the other our garage attached to a neighbours garage (over which they've built a two storey extension).

We're putting a rear extension on and looking to bring the pitched roof round in an L shape over the length of the existing garage (using hip roof) to replace existing flat roof.

Now, if we go for a pitch over the garage, the lower edge will need a gutter and also tying in to next doors extension. I have seen this done whereby the gutter sits on top of the wall and then felt or similar is laid underneath the gutter and tied in to a course of mortar on the neighbours extension.

My questions are: 1) is this the best method? 2) Anything else better to use in this instance than felt?

We have some concerns around damp penetrating between the two 'garages' (the rear half of both will be occupied by living space) via the gutter and felt approach.

I have attached an illustration, the red line indicates the position of our proposed roof line - hope it makes sense!

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• chopkins13
• 28 Jun 2013
• 1

Thanks in advance for any comments/suggestions.

Chris

 

[freddiemercurystwin]

There's nothing special or particularly tricky about it, its a standard roofing detail:

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• freddiemercurystwin
• 28 Jun 2013
• 2

Lined with lead would be the best choice though GRP could be used.

 

[chopkins13]

Hi, thanks for the swift reply - the diagram is great and exactly what I had in mind! Just a couple of questions:

1) What are the advantages of lead over GRP or felt?

2) if using lead, would this be one long roll the length of the garage/extension (this would be about 13 metre run in total) or would you lay it perpendicular to the run of the box gutter, overlapping against the direction of the fall?

3) would it be possible (almost has a double insurance method here) to fit normal plastic guttering within the created box gutter? The idea being that the plastic guttering will take most of the water which comes from the pitched tiles and then the box gutter underneath deals with any direct rainfall into the box gutter/onto the neighbours wall and as a back up incase the plastic gutters were to become blocked?

Any further input you can provide will be very gratefully received!

Cheers,

Chris

 

[freddiemercurystwin]

Lead will last longer though unless you are planning on not moving for 25+ years that shouldn’t really be an issue though is of course attractive to thieves. Lead is much easier to manipulate and the various imperfections that buildings can presents can be much more easily absorbed by leadwork rather than grp. Though if the existing building is not all over the place then that too is not much of an issue.

If lead, for a 13m long gutter it either needs to be stepped (which can be difficult to achieve) or ‘T Pren’ joints be introduced.

No need to bother with an additional plastic gutter if the box gutter is properly constructed and maintained.

 

[tony1851]

2) if using lead, would this be one long roll the length of the garage/extension (this would be about 13 metre run in total) or would you lay it perpendicular to the run of the box gutter, overlapping against the direction of the fall?

Not adviseable to lay lead in one long strip of that length due to thermal problems. Try doing it in two sections with a 2" drip approx half-way down.

 

[chopkins13]

Thanks for the responses guys - I've googled the T-Pren and that seems fairly self explanatory, can I just ask, what is a 2" drip? Is this the same as putting a couple of 'steps' into the run of leadwork?

just wanting to get everything clear in my head before discussing this (and a variety of other issues) with the potential builder we've got lined up - thought it best I had done my research so I can understand his proposed approach!

Cheers,

Chris

 

[tony1851]

can I just ask, what is a 2" drip?

It's just a step down in the gutter, to avoid having a long continuous run of lead which could buckle on a hot day.

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• tony1851
• 1 Jul 2013
• 1