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Edpm at edges


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16 minutes ago, JSHarris said:

If it were me I'd want the EPDM well-protected from damage.  Having it encapsulated under concrete makes it pretty much bomb-proof, and far less likely to be damaged than having it partially exposed.  If it does get damaged in the exposed areas then I would guess that sods law says that the whole membrane will need replacing, including the area under the concreted bit in the middle, so just as much work to fix.

 

There's no difference between an encapsulated roof membrane like this and the DPM under our concrete slab, that keeps the damp out.  If our DPM fails then the whole house has to come down in order to fix it, as the slab runs under our walls.  What's more, our DPM is a much thinner sheet of polyethylene, nowhere near as robust as a 1.5mm layer of EPDM.

If exposed edpm gets damaged I thought it could be fixed / patched ?? 

After all that was the original plan on the upstands 

Edited by pocster
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3 minutes ago, pocster said:

If exposed edpm gets damaged I thought it could be fixed / patched ?? 

After all that was the original plan on the upstands 

 

Depends.  If the damage happens near the concreted part than you may well not have a large enough overlap area for any patch to seal properly, which may mean taking up the concrete.  It's hard to see how a membrane embedded in concrete could get damaged, especially given the flexibility of EPDM.

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11 minutes ago, JSHarris said:

 

Depends.  If the damage happens near the concreted part than you may well not have a large enough overlap area for any patch to seal properly, which may mean taking up the concrete.  It's hard to see how a membrane embedded in concrete could get damaged, especially given the flexibility of EPDM.

I take your point . Most likely failure point though must be edges / flashing . Also the stilted solution means no water at skylight level - skylight never gets swamped in water . Trying to solve multiple problems with this scenario ?

Edited by pocster
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You don't have sitting water on your DPM. Totally different scenario. It's to stop damp coming up not water getting down through it. If having the membrane under concrete was a good idea they would do it on commercial roofs and I've never seen it done in 36 years.

Edited by Onoff
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10 hours ago, Onoff said:

You don't have sitting water on your DPM. Totally different scenario. It's to stop damp coming up not water getting down through it. If having the membrane under concrete was a good idea they would do it on commercial roofs and I've never seen it done in 36 years.

 

My point is that we have no evidence at all that thin, relatively inflexible, polyethylene DPM sandwiched between layers of concrete ever suffers from any degradation over decades of use, so I can't see any mechanism by which a layer of more robust and flexible EPDM could be a problem when protected this way.  This is a drive/parking area, not just a roof, so any waterproofing solution needs to be able to tolerate that sort of wear and tear.  In particular, EPDM is poor at tolerating point loads, as might be the case for pavers on pillars, something that seems to have been solved by spreading the imposed load over a wide area with the reinforced concrete capping layer.  The architect's solution seems to be sound, in that the waterproof layer never gets exposed to wear and tear, as it's encapsulated within reinforced concrete.  What wasn't sound was the implementation of the design; all the problems here seem to be caused by poor workmanship, I can't yet see any problem that is a consequence of the design itself.

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I think I have a solution .

Agree that the edpm protected is best - but nice to be able to find a leak and get to it if an issue .

One thing I never liked was the water running level with the glazing . The stilts offer perfect drainage solution for that . This stilt on edpm is used ( forgetting vehicle’s ) plenty of examples for terraces / roof gardens etc . I guess the edpm could be ‘protected’ via some other means ; or perhaps a thin layer of concrete . 

That way edpm protected . Stilt sits on thin concrete layer . Glazing has zero drainage issues - water can never get that high .

When I break back to the 35mm concrete - obviously this will be damaged and cratered . It could then be screeded with a fall to the front and a ‘channel’ made in the form work . Rubber over the lot means even the channel gets water proofed and is built in .

This sounds like all requirements are met ; yeah ?? ?

Edited by pocster
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In section I imagine the edpm in effect comes along horizontal then turns through 90deg up the side of the upstand. I'd be particularly cautious / worried about driving on the paving close to that upturn's internal corner and splitting it. 

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20 minutes ago, Onoff said:

In section I imagine the edpm in effect comes along horizontal then turns through 90deg up the side of the upstand. I'd be particularly cautious / worried about driving on the paving close to that upturn's internal corner and splitting it. 

Yeah 

i think the architect wants the ‘parking area’ to have a raised kerb at the edges .

You could still drive over it ; break the tile and stilt then embed your wheel in my rubber roof ?

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Yep - they can follow the slope 

Also have a ‘rounded’ foot so don’t damage edpm . Think I’ll protect the edpm anyway - see what rubber guy says . Will use pavers for the suspended sides . These elongated driveways blocks will be just on the parking area .

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14 minutes ago, PeterW said:

 

Is he flexible in his approach .... 

Assume that was a joke !

He fully understood the issues ( without me leading him to them ) . I think he’d rather grp - but I have to concrete on that in the centre .

He’s going to get back to me but admitted his gut reaction was to walk away from it . ?

Edited by pocster
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3 minutes ago, pocster said:

Assume that was a joke !

He fully understood the issues ( without me leading him to them ) . I think he’d rather grp - but I have to concrete on that in the centre .

He’s going to get back to me but admitted his gut reaction was to walk away from it . ?

 

 

Didn't we have a discussion about using GRP for this some time ago?  GRP certainly has a lot of advantages, especially when it comes to getting a really robust seal around those upstands, and at the more complex edge detailing, like that by the gate/entrance, but it does need dry weather, and ideally needs to be done when the air temperature is reasonably warm, and consistently so for the whole of the cure time.  There's no doubt that a good GRP roof will be a lot tougher and take a fair bit more abuse than an EPDM roof, though, plus it's easier to patch repair any small areas that may get damaged.

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10 minutes ago, JSHarris said:

 

 

Didn't we have a discussion about using GRP for this some time ago?  GRP certainly has a lot of advantages, especially when it comes to getting a really robust seal around those upstands, and at the more complex edge detailing, like that by the gate/entrance, but it does need dry weather, and ideally needs to be done when the air temperature is reasonably warm, and consistently so for the whole of the cure time.  There's no doubt that a good GRP roof will be a lot tougher and take a fair bit more abuse than an EPDM roof, though, plus it's easier to patch repair any small areas that may get damaged.

Yes we did . My architect was against it because he was concerned about concrete onto grp ; the mass of that 35mm reinforced concrete . Now though it’s only the parking area that would have concrete on it . No idea if my architect will be happy with this . Went down the EPDM routine because that’s what he wanted .

As my architect said too me a few days ago “ it’s a learning curve “ - yeah , for both of us but with my money ? ?

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Sorry I don’t get why your architect has no issue with using a compressible material between two layers of fixed concrete, but is not happy to use something rigid ..???!

 

I am starting to think he’s designed something that can’t be built and he’s backing away from something of his own creation. 

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Just now, PeterW said:

Sorry I don’t get why your architect has no issue with using a compressible material between two layers of fixed concrete, but is not happy to use something rigid ..???!

 

I am starting to think he’s designed something that can’t be built and he’s backing away from something of his own creation. 

 

 

That issue of compressibility, together with the greater robustness of GRP, was what had me puzzled from the start.  I will admit to being a fan of GRP roofing, having done a couple and seen just how tough and durable it is.

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4 minutes ago, PeterW said:

Sorry I don’t get why your architect has no issue with using a compressible material between two layers of fixed concrete, but is not happy to use something rigid ..???!

 

I am starting to think he’s designed something that can’t be built and he’s backing away from something of his own creation. 

Quickly googling grp it does suggest it needs to be allowed to expand / contract . Is that an issue for a slab of concrete with a car on it ?

Who knows what my architect thinks ! 

I did think of a solution ( assuming car and concrete on grp are an issue ) . Could build off the 30mm concrete and have a steel structure just for the car area . Then grp /EPDM wouldn’t be under it . But I’m just shooting air at this point ..... ?

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20 minutes ago, JSHarris said:

EPDM and glass fibre laminate are not that different in terms of their coefficient of linear thermal expansion, plus I doubt there would be much of a temperature change underneath that layer of reinforced concrete and pavers, anyway.

I guess the question then is can you put concrete and weight of a car on it ? . Question for SE rather than architect I suspect .....

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Just now, JSHarris said:

 

 

No problem, it has significantly better load bearing properties than EPDM. 

Than I have NO idea why my architect ignored it as an option !!! ????

One problem though what would go under the parking area for the grp to fix too ? I assume it can’t be applied direct to concrete ????

Sigh ! 2 steps forward ; 1.98 steps backwards ....

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1 minute ago, pocster said:

Than I have NO idea why my architect ignored it as an option !!! ????

One problem though what would go under the parking area for the grp to fix too ? I assume it can’t be applied direct to concrete ????

Sigh ! 2 steps forward ; 1.98 steps backwards ....

 

I thought the EPDM was over cement board and then the concrete was over the top of that?

 

Anyway, GRP can be laid over concrete, just needs the concrete to be primed with G4 first.

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