Options for a shallow roof pitch

scottishblondie

We bought a property last year with a large extension build in 2014. About 2 weeks later we discovered the roof was letting in significant amounts of water. Subsequently we found that the design of the roof is seriously flawed - it has areas where the pitch is as shallow as 7 degrees, but has been finished with Marley tiles which are rated for a minimum of 15 degrees.

I've sketched up a representation of the roof design below. The elevation is first and then a top down view. The red areas are the problem. Currently only the area 2nd from the right is letting in enough water to be noticeable, but we will need to do the entire roof as the whole thing is flawed.



I'm looking for some ideas as to how to fix this. We've had roofers out to look at it and had a few suggestions, but we're not sure where to go from here. Currently the whole thing is covered in black plastic to keep the water out, but it's been a year and we really need a permanent fix!! The property is a 1920s villa with red rosemary tiles on the roof, and we don't want to use a covering that will look terrible against the main house.. The main suggestions have been:

1. Felt
2. EPDM
3. Felt + tiles relaid over
4. EPDM + tiles laid over
5. Metal (zinc/copper)
6. Rebuild the roof with a steeper pitch

We've been both recommended and advised against relaying the tiles over the top of whatever covering we go for. Puncturing the thing keeping the water out doesn't sound like the smartest move, so although the tiles would look best they probably aren't going back on.

EPDM sounds like a great option, but I've not been able to find out if you can get it in red. We have a recommended installer coming out to take a look in a couple of weeks to talk us through this.

A metal finish is an interesting idea and would look quite swish, but I feel the cost might be too high. I've not yet managed to get a roofer who specialises in metal roofs out to have a look.

Rebuilding the whole roof sounds not only stupidly expensive, but also very disruptive. There is, however, plenty of room beneath the upstairs windows to raise the pitch significantly. In truth if money were no object I would love to do this, as I don't really like the current design :rotfl:

Does anyone have any suggestions of other options or opinions on the suggestions we've had so far? Thanks.

Heedtheadvice

Flat or near flat roofs can often be a major pain in the derrièr!
All solution are subject to puncture risk, metal probably the easiest to repair if needs be.


Esthetically you might consider a resilient seal layer (EPDM, metal, or fibre glass) with then battens, sealed below onto your waterproof layer with gasket material or silicon sealant with the first of the two batten layers in a direction allowing run off and the second above at right angles to fix back your existing tiles.


Note that this is only an idea. Doozer may be alog with real building experience and I wouls also consider passing it by building control for their comnents on change of design.


Last thing I would do is use felt!!!
There are modern breathable waterproof membranes to do the same job as felt much better but not at 7degrees pitch!!

Kiran

If the pitch of your roof is too shallow for tiles to work then you can EPDM the roof, counter batten and then reuse your existing tiles.


https://www.rubber4roofs.co.uk/can-i-install-roof-tiles-over-the-rubber-membrane


This is a reasonably common thing to do when you want the roofs treatments to look the same when you, for example, create shallow but not flat dormers

Doozergirl

Could you post a picture of the actual house too, please?

My first thought was exactly what Kiran has said above; we've certainly done that in the past.

But without seeing the house, one can't comment on what would actually suit it.

scottishblondie

Doozergirl wrote: »

Could you post a picture of the actual house too, please?

My first thought was exactly what Kiran has said above; we've certainly done that in the past.

But without seeing the house, one can't comment on what would actually suit it.

I only have this very small grainy photo from the EA brochure at the moment, I'll take a better one when I get home from work. The house is split into 2 flats, we are (obviously!!) the ground floor property.



Battening and putting the tiles back on top of EPDM was suggested, but then another roofer said it was a terrible idea as we would be making holes in the stuff keeping the water out!

Kiran

The battens are fixed parallel to the slope of the roof so the holes are covered by the batten. This would be enough water takes the path of least resistance i.e. down the slope of the roof. If you wanted a robust detail then you would put lap sealant under the batten. This would seal up around any fixing holes and a line of lap sealant between the batten and the epdm. This would be considered overkill in normal circumstances but if you are in extremely exposed location could be worthwhile

Doozergirl

Get rid of those gables. There is zero point going to the effort of keeping something so architecturally irrelevant. Architecture is based on keeping the house standing and dry, primarily. No one has ever built like that - it isn't a detail that has ever been used in this country because it doesn't work to keep things dry! It's not referring to a period, does not enhance the character of the building and can therefore be removed.

Without meaning to be rude, the single storey extension has the look of a static caravan parked in front of the house, and it is crying out to lose the gables.

It would look better as a flat roof, with the downpipes at either end, instead of cluttering the face of the building. The other upside is that it totally removes all the additional risks and costs associated with numerous gables - even on regular houses without the silly pitch. 7 degrees is fine for a 'flat' roof as they aren't actually flat!

EDPM with a sensible fascia cladding around it will make it look respectable.

If you want it more 'built' then you could build the walls up to parapets and hide the flat roof behind. They do that in London a lot. Wth a rendered finish, it would compliment what appears to be a 1930s detail on the main roof.

Someone's random Pinterest board features both types although they've labelled the board as parapet roofs. The parapet ones are where you only see the wall, rather than any fascia around the building.
https://www.pinterest.com/lkimpton/parapet-roof/

Metal clad roofs are a great feature but don't match those curved windows. I'd be doing more to modernise the look of the extension if that's something you're keen to have.

FreeBear

scottishblondie wrote: »

The house is split into 2 flats, we are (obviously!!) the ground floor property.

Based on the above, I'm guessing this is a leasehold property ?
If so, who is responsible for the maintenance of the building ?
Are you going to need permission for any alterations to the external fabric ?

scottishblondie

FreeBear wrote: »

Based on the above, I'm guessing this is a leasehold property ?
If so, who is responsible for the maintenance of the building ?
Are you going to need permission for any alterations to the external fabric ?

We are in Scotland, so not leasehold. Commonhold, I think is the term? Anyway, the deeds of the property state that both owners are jointly responsible for the fabric of the main building, costs to be shared 50/50. We are solely responsible for the fabric of the extension. I don't think we need permission from the upstairs neighbour to alter the extension, but he seems amenable to whatever we want to do. We actually bought from his older brother, and he has repeatedly told us "I warned him that roof was no good!". They didn't get on.

We may need planning permission for the alterations, depending how far we decide to go, as being a flat we have no permitted development rights.

scottishblondie

Doozergirl wrote: »

Get rid of those gables. There is zero point going to the effort of keeping something so architecturally irrelevant. Architecture is based on keeping the house standing and dry, primarily. No one has ever built like that - it isn't a detail that has ever been used in this country because it doesn't work to keep things dry! It's not referring to a period, does not enhance the character of the building and can therefore be removed.

Without meaning to be rude, the single storey extension has the look of a static caravan parked in front of the house, and it is crying out to lose the gables.

It would look better as a flat roof, with the downpipes at either end, instead of cluttering the face of the building. The other upside is that it totally removes all the additional risks and costs associated with numerous gables - even on regular houses without the silly pitch. 7 degrees is fine for a 'flat' roof as they aren't actually flat!

I would tend to agree. The inside space it gives is incredible (humungous open plan U-shaped kitchen/dining/living room) but it is not really attractive. I wouldn't even know what to call the style of roof, and I really do wonder what the architect was thinking. Fortunately we don't spend a lot of time gazing at it from the back garden!

I love the flat roof with the lantern. One thing that is missing inside is the the old living room is now completely internal and quite dingy. There are no roof lights, so the light from the windows struggles to get all the way back.

As much as I would love to change the look, I'm just not sure how feasible it is. I know anything is possible with enough money, but rebuilding the entire roof structure seems like it would be pretty expensive?

Also, better pic below... although you've probably seen enough :rotfl:

scottishblondie

Kiran wrote: »

The battens are fixed parallel to the slope of the roof so the holes are covered by the batten. This would be enough water takes the path of least resistance i.e. down the slope of the roof. If you wanted a robust detail then you would put lap sealant under the batten. This would seal up around any fixing holes and a line of lap sealant between the batten and the epdm. This would be considered overkill in normal circumstances but if you are in extremely exposed location could be worthwhile

Thank you that makes sense. We aren't terribly exposed as we are in a flat built up area and have large hedges/trees around the garden, but then again we also have school playing fields on 2 sides so the wind can get up a bit.