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Discussion Starter · #1 ·
Hello,
This is not a DIY project, but I have searched online and you folks seem the smartest, so I hope you're willing to offer your collective 2 cents....

Background:
1982 house built into a hillside, the roof is a "green" or "sod" roof, and in my opinion very poorly designed (the drainage is very poor, and I think they put about 10" of plain, sandy, extremely heavy topsoil up there - it's impossible to keep grass alive without excessive irrigation which obviously isn't ideal). We bought the house 5 years ago and have been hammered with some really heavy snowfalls the past few winters. When the snow melts, we get 3 separate leaks on our main floor (2 very minor, 1 slightly worse). I don't believe the leaks are "severe", but only leak when there is pooling water more than an inch or 2 deep. The renovation area is just under 3,000 square feet and includes our entire upper level and attached garage.

I've talked to a few roofers and contractors and everyone agrees it's time to replace the current system, patching would be a waste of time, money, and energy. I hope you guys can help me decide which repair sounds best.

*I do have a few doorways with 45 degree cracking in the drywall and an area of kitchen floor with a downward slant (I can probably upload photos if anyone wants to see the extent). My understanding is these can be a sign of structural damage/weakness/sinking and plan to get a structural engineer out prior to committing to anything. Having said that, I'm pretty sure all the cracks have been present since we bought the house 5 years ago -- the inspector prior to purchase didn't seem too worried about any of this, and I don't believe they've gotten any worse. My hope is that reducing load on the roof and dealing with the leaking will hopefully help with further damage? We can probably afford to spend an additional several thousand to fix structural issues that arise with any of the below quotes.

Options:
1) Wedge insulation with TPO cover. This is probably the simplest fix; getting custom-cut heavy duty foam, and slapping a TPO membrane over top. Approximate cost quoted was $22,700, not including excavation or drain installation. 15 year warranty on membrane.
2) Truss system with very heavy duty TPO membrane (roofer says lifetime parts and labor warranty, transferrable once). This is a more "complete quote" as it includes excavation, vapor membrane, stem wall installation, and French drain installation to deal with runoff. Cost quote: $45,700. I could upgrade to a metal roof for roughly $8,000 more.
3) Build a true attic with metal roof that could be upgraded later to additional living space (would add roughly 1500 square feet). I'm still waiting on a quote from someone who came and looked at the house 2 days ago. He seemed intimidated by the scope of the job, and I think he is going to say "thanks, but no thanks". Earlier I got a quote from a contractor to get a basic truss up and insulated floor for $35,000, but that contractor seems to have vanished -- I wonder if he undershot his bid and has since ghosted me.
4) Replace the green roof. A local structural engineer recommended this, using a local ag construction company and their heavy duty pond/reservoir liners. Apparently the lifespan of those liners in the sun is about 25 yrs, but maybe indefinite if protected from UV light. The proposed system right now is to place a liner, then use rock to create a better slope off the house, place a second liner, then sod on top. Cost: $31,700 including excavation, drain installation, and re-sodding. I am very worried about excessive weight on my stressed roof, so if I went this route, I'd spend more to get tapered foam insulation instead of rock to minimize weight on the roof, and would probably need to pay for engineered fill rather than topsoil, and also pay for sedums to install on top (so cost may be closer to $40-45,000 -- I'm still doing homework on added cost of better/lighter components than what's on the initial quote).

Obviously cost is always a concern, but I don't want to "cheap out". We do live below our means and have been saving aggressively since buying the house in anticipation of this dreaded renovation. Our goal is to get as close to a permanent fix as possible, while retaining as much insulation benefit as possible -- this is a large house.

I'll be curious to hear everyone's thoughts, and thank you all for reading my novel :)
 

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Hammered Thumb
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I can probably upload photos if anyone wants to see the extent
Yes, especially the exterior!

but only leak when there is pooling water more than an inch or 2 deep.
Flat(ter) roof then? 3 of the 4 solutions is abandoning the sod roof. Is there a preference? I would assume you bought it so the sod attracted you in the first place.

PS location - Seattle Mariners?
 

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retired framer
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Do we know what the structure of the roof is? Can we assume the back wall is concrete.
 

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Discussion Starter · #4 ·
I'll get pictures uploaded ASAP. I'm home alone with the kids today, and the baby has RSV so it'll be tough to upload unless he takes a decent nap.

I think it is nearly perfectly flat. There might be a slight slope towards the front of the house, then slope off the side of the house, but the drainage system is really insufficient. I think it was an afterthought, perhaps even after previous water damage that wasn't disclosed at sale.

Location: Eastern WA state, yes, go Mariners (maybe next year). It is typically hot/dry in the summer months, small amount of rain spring and fall, and usually a couple inches of snow in winter. 2 of the last 4 winters we've received a couple FEET of snow, which is unheard of out here.

I'm not particularly attached to the green roof. We were attracted to the house for the view, attached land, and sale price more than the green roof. I'm not sure how much energy the roof saves us; it seems like if we have prolonged cold or hot spells it almost makes heating and cooling worse.

I am pretty sure all the foundation in contact with the hillside is cinder block; I'm not sure about the front of the house. There's so much weight up there right now I'm assuming concrete. There are some 2X6 pillars holding up the garage and running down the porch, I don't know how much of the main structure weight bearing they are doing.
 

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retired framer
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So you could sneak a peak thru the ceiling and see if it is plywood or concrete from below? If you have had leaks you have to fix that anyway?
 

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Discussion Starter · #6 ·
So you could sneak a peak thru the ceiling and see if it is plywood or concrete from below? If you have had leaks you have to fix that anyway?
I suppose I could if necessary -- it'll probably be about 3 months before it will be repaired, so I'm a little hesitant to punch a hole through it just yet.

I just had a contractor and roofer come out to survey the internal damage and they were very impressed with the general build quality of the house -- neither of them seemed to think it was remotely unreasonable weight-wise to build up. Am I right in assuming a concrete roof is going to be able to withstand a much heavier load? A discussion I had with a structural engineer who hasn't actually seen the house said it almost has to be concrete/rebar with the current load up there.
 

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retired framer
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I suppose I could if necessary -- it'll probably be about 3 months before it will be repaired, so I'm a little hesitant to punch a hole through it just yet.

I just had a contractor and roofer come out to survey the internal damage and they were very impressed with the general build quality of the house -- neither of them seemed to think it was remotely unreasonable weight-wise to build up. Am I right in assuming a concrete roof is going to be able to withstand a much heavier load? A discussion I had with a structural engineer who hasn't actually seen the house said it almost has to be concrete/rebar with the current load up there.
That is what we do with a bonus room under a garage. but I have seen two that was concrete over wood.
 

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If you need help I can always take a look and give you options. Green roofs have many benefits and have improved a lot since that one was installed.
 

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Discussion Starter · #9 ·
Hi guys -
Punched a hole in the garage where there's some water damage and I can see what looks like plywood. It's an awkward spot so it's hard to get a very good look at much of the crawl space.

I'm definitely entertaining the idea of keeping the green roof -- does it sound reasonable to you to have a pond/reservoir liner used as the waterproofing membrane? It seems cost-effective, but lack of testing in this scenario has me nervous. Additionally, the contractor proposing this has no experience doing a project like this, but said he has "no concerns" -- he said he uses thousands upon thousands of square feet of this stuff yearly and said my roof shouldn't be much different.

Still working on getting pictures -- hopefully this afternoon, during our freak snowstorm
Thanks
 

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Discussion Starter · #10 ·
Here are a few pictures for you all. The trees to the right on a few pictures are about 5-6 feet away from the back wall of the house. I tried to get a picture of the poorly designed drain system, and the "spray foam" that people seem flabbergasted was used on top of the waterproofing. The picture of the edge of the house is right where one of the leaks is, you can kind of see where they've tried to "re-waterproof" an area with some sort of rubbery grey material.
 

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I was excited by the idea when I was young but no longer more i read about it over the years and finding out that nature is not easy to reproduce. Anyway, if it was mine, i would remove it and make it into a regular roof for time tested reliability. I may be tempted to cover it with cheap corrugated metal roof and weigh them down with pots of plants.:smile:
Such roof, more i thought about them, is full of contradictions. Must be light enough, but has to be insulating and shed water. Must support plants but must shed water (airy soil vs hard soil), initial weight bearing over building, fertilizer, probably frequent inspections and the maintenance, etc. I don't even see ecological benefit. If it's the "hobbit hole" appeals, the author was no carpenter.:smile:
 

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Discussion Starter · #12 ·
Such roof, more i thought about them, is full of contradictions. Must be light enough, but has to be insulating and shed water. Must support plants but must shed water (airy soil vs hard soil), initial weight bearing over building, fertilizer, probably frequent inspections and the maintenance, etc. I don't even see ecological benefit. If it's the "hobbit hole" appeals, the author was no carpenter.:smile:
It definitely has unique needs that are hard to fill (particularly the soil substrate). It's so dry out here the roof isn't doing much with regards to preventing large run-offs of water -- I have to irrigate all summer, which is something I don't like in a drought year, like last year. I suppose with sedums, once established there'd be less work. I'm not super convinced about insulating capacity either -- thermal barrier yes, but it seems like once all the dirt cools or warms up my hvac system has to run more than it otherwise would.

The benefit is that this is the cheapest fix proposed, and it does look nice when maintained (and our roof is extremely visible). I don't mind doing yard work, but am at a stage in life where I'm just too dang busy as is.
 

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I think pond liners are about the same as the rubber roofs. Rubber roofs, however, have developed glue joint problems, if not in one piece. These days, it comes with some kind of joint tape, but I'm not sure if this is time proven.

I like the foam underlayment solution the best. Tapered foam blocks can add insulation value if thick enough, then you can use whatever flexible roofing you want. TPO joints, I think, is sealed by melting the overlapping sheets with hot iron or such. I've read that this joint can fail if not done by someone with lots of experience. Ask your roofer for demonstration as well as his command of the method. The cost is probably the high cost of the materials. You can opt for SBS modified roll roofs which may be cheaper and has more than 15 years life span. In nj and diy. Cold glue tamko sbs roof with its base sheet. Not a good memory:smile:, and it is under partial shade, but going on nearly or bit over 20 years and doing well.
Since your roof must have been over built, you can opt to cover the roof with a floating deck that can shade and lengthen the roofing life.
BTW, for excavating, I assume it has to be done by hand?
 

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retired framer
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I think pond liners are about the same as the rubber roofs. Rubber roofs, however, have developed glue joint problems, if not in one piece. These days, it comes with some kind of joint tape, but I'm not sure if this is time proven.

I like the foam underlayment solution the best. Tapered foam blocks can add insulation value if thick enough, then you can use whatever flexible roofing you want. TPO joints, I think, is sealed by melting the overlapping sheets with hot iron or such. I've read that this joint can fail if not done by someone with lots of experience. Ask your roofer for demonstration as well as his command of the method. The cost is probably the high cost of the materials. You can opt for SBS modified roll roofs which may be cheaper and has more than 15 years life span. In nj and diy. Cold glue tamko sbs roof with its base sheet. Not a good memory:smile:, and it is under partial shade, but going on nearly or bit over 20 years and doing well.
Since your roof must have been over built, you can opt to cover the roof with a floating deck that can shade and lengthen the roofing life.
BTW, for excavating, I assume it has to be done by hand?
I am not surprised that you say trouble with contact cement used on rubber. I spent a few years in the rubber business and any cold glue for rubber is always more like the inner tube patching where you scuff the surface and use a special 2 part glue and rolled down tight.
 

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So took some studying of these to figure this out, but not sure I have it so drew on your pic. Is this right?

- you have a 3' high or so parapet with a "mansard-like" metal roof on the front for looks?
- why was the drain pipe added at the bottom of the parapet wall (gravel transition is good) if the roof is sloping back towards the tree?
- are any of the leaks at the back wall, since there would be more opportunities where the roof meets the back CMU wall for water intrusion?
- how much does the grade slope down beyond the back house wall?

First thing, that tree and all that brush should not be anywhere near your house. The roots are extending out on top of your roof and will penetrate the membrane. I would keep clear at minimum 20' or so with just grasses.

Going back to your options, No.3 of adding 1500sf with trusses. You have a 3' or so high parapet, so are you talking about putting a whole gable or something then, with a new back wall, and assuming the existing roof structure is either adequate converting to a 3rd story floor or eliminate it altogether?

I think if you were to choose a non-sod roof, you need a parapet wall on the back to raise it so it can drain onto the grade. And maybe a fence to discourage animals and kids to not damage an easily accessible roof.

For a green roof, you need a root protection layer and drainage mat over the waterproof membrane. It is also better to insulate the exterior side. So for that, and warranty and any penetration/termination bar details, I would probably avoid the pond liner idea (although I haven't researched it for this use).

If you are intent on replacing the entire roof, I don't know which one I'd go with yet. You probably aren't going to recover this huge cost. It seems that having the green roof contributes to the house's valuation here, but redoing it would be a lot of work. The other options, if just merely done to replace the sod, could detract from value, whereas if they were designed to say allow a vaulted ceiling, or incorporate skylights/transom windows, might add extra value then.
 

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Discussion Starter · #16 ·
I think pond liners are about the same as the rubber roofs. Rubber roofs, however, have developed glue joint problems, if not in one piece.

I like the foam underlayment solution the best. Tapered foam blocks can add insulation value if thick enough, then you can use whatever flexible roofing you want. TPO joints, I think, is sealed by melting the overlapping sheets with hot iron or such.

BTW, for excavating, I assume it has to be done by hand?
1) the pond liner (polypropylene, probably 60 or 80-mil) is heat welded, the construction crew that would do the work does this all day, every day so he had no concerns about failing seams or the like. He said my roof is about the right width for 2 full-width rolls, so would have just 1 heat welded seam
2) I'm liking the foam solution as well, seems cheaper, with benefit of insulation. The issue I have is that I don't really want a flexible roof membrane if I can avoid it. Would it be possible to overlay the foam with something (plywood?) then put down metal? I assume there'd be concerns about wind blowing everything off unless there's a simple solution for fastening the wood layer securely.
 

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Discussion Starter · #17 · (Edited)
So took some studying of these to figure this out, but not sure I have it so drew on your pic. Is this right?

- you have a 3' high or so parapet with a "mansard-like" metal roof on the front for looks?
- why was the drain pipe added at the bottom of the parapet wall (gravel transition is good) if the roof is sloping back towards the tree?
- are any of the leaks at the back wall, since there would be more opportunities where the roof meets the back CMU wall for water intrusion?
- how much does the grade slope down beyond the back house wall?

First thing, that tree and all that brush should not be anywhere near your house. The roots are extending out on top of your roof and will penetrate the membrane. I would keep clear at minimum 20' or so with just grasses.

Going back to your options, No.3 of adding 1500sf with trusses. You have a 3' or so high parapet, so are you talking about putting a whole gable or something then, with a new back wall, and assuming the existing roof structure is either adequate converting to a 3rd story floor or eliminate it altogether?

I think if you were to choose a non-sod roof, you need a parapet wall on the back to raise it so it can drain onto the grade. And maybe a fence to discourage animals and kids to not damage an easily accessible roof.

For a green roof, you need a root protection layer and drainage mat over the waterproof membrane. It is also better to insulate the exterior side. So for that, and warranty and any penetration/termination bar details, I would probably avoid the pond liner idea (although I haven't researched it for this use).

If you are intent on replacing the entire roof, I don't know which one I'd go with yet. You probably aren't going to recover this huge cost. It seems that having the green roof contributes to the house's valuation here, but redoing it would be a lot of work. The other options, if just merely done to replace the sod, could detract from value, whereas if they were designed to say allow a vaulted ceiling, or incorporate skylights/transom windows, might add extra value then.

Sorry, I didn't think to label anything. You're pretty well spot-on with regards to boundaries and such.

- The parapet wall is probably closer to 4.5-5 feet tall. The metal portion overlies our deck and provides shade in the summer months (but doesn't extend far enough to block sunlight in the winter).
- You're making a very understable, but false assumption. The drainage goes TOWARD the parapet wall (or at least what I think is excessive amounts of drainage heads that wall). During snow melt, the snow gets trapped up against that parapet wall because the French drain wasn't installed with a consistent slope, or it has settled through the years.
- There are also 3 additional French drains underneath the sod running transverse across the house, seemingly to push drainage to either the front or back of the house. These are installed extremely poorly, some areas are within 1" of the top of the soil line; I don't think they do anything.
- The grade behind the back wall is fairly steep (I don't have an exact number, but seems almost as steep as a traditional shingled roof), once water gets off the house it runs off very quickly; it's just a matter of getting it off which is the big issue right now. There is 1 leak on the back side of the wall, over the garage. That parapet wall wraps around the edge of the house behind where I took pictures (the close up of where some of the dirt is dug up is where the leak is). All other leaks run to the front of the house, presumably because that's where the water runoff was designed to go (facepalm)

- Every contractor I've spoken to said the trees have to go, so I agree they aren't long for this world. I was thinking of replanting a few blueberry and asparagus plants in their place, but if those root systems are too extensive, I'll not do that either. I'd probably put down gravel if grass is the only other option
- RE: option 3 - I'm not entirely sure what the exact proposal would entail. I should get a detailed quote on a few different options sometime this week, and once received, will try to upload them. There's been talk of pouring a stem wall, and also talk of putting down new floor joists over the failing membrane. (I think basically dig down to the membrane, then essentially build a new structure on top of the old).
- RE: Green roof replacement - agreed on the drainage layer and root layer, talked to the contractor about these a bit already. He's on board, but said he doesn't worry about root penetration with this membrane (I'd still be willing to spend a few extra bucks on it though). For insulating the "exterior" do you mean it's worth insulating on top of the waterproof membrane?

Honestly, I think the green roof detracts from the house's value. When we were house shopping, this house was about 2x the size and had 3-4x more land than the other houses in this price range, plus we're not WAY out in the boonies or stuck in the middle of town, like the other options we looked at. I think the non-traditional build scared people away...maybe they foresaw a huge renovation bill in their future :vs_no_no_no:. I suspect if we can slap something up there that doesn't massively increase the heating/cooling bills and will either last a really long time, or be cheap to fix, we'll end up ahead on resale value. We went with buying this house, and have been saving aggressively in anticipation of this, so it's all good :smile:

I appreciate all the thought you folks are putting into my dilemma.

EDIT for previous post - about half of the folks I've talked to want to drive an excavator down and use the bucket to shovel off as much as they can reach without driving on the roof, then hand dig the rest. Considering there may be almost 90 yards of soil and rock up there (roughly 28 ft X 100 ft X 8-10 inches deep), that'd save a lot of labor costs.... EDIT2 - used an online calculator to confirm 70-85 yards depending on soil depth. That's over 100 TONS when wet, which, since drainage is terrible up there, is probably usually the case.
 

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Discussion Starter · #18 ·
I guess I didn't include the picture of the leak on the back side of the house over the garage. Here is the leak on the back side. You can see the ~4 foot strip of parapet, this is located on the back side of the house and was a really bad area for water to get trapped before I dug that little trench you can see.
 

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I'm guessing these points. I have zero experience with metal roofs or removing earth piled on frame construction floors.
1. In nj and not too many metal roofs. Ones I see have fairly steep slopes. Usual metal roofs go on in pieces therefore full of open seams. I am conditioned by my area to worry about such roofing on flat to little slope roof.
If metal roof, I would assume that the roof will be rebuilt with truss to give proper slope.


2. I think you asked a roofer, so got roofer's answer about removing the earth. I'm not saying the roofer is wrong, but he may not have the experience or the equipment. Example, a garage floors where a car can be parked have been built, although they didn't last long. Your earth roof should have been built with that weight in mind, so I think it's worth exploring if hand driven excavators or such can be used on your roof system. Even if you have to lay down plywood sheets for a "road". Should at least save some time. If calculating, lots of safety margin.
 

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Discussion Starter · #20 ·
I'm guessing these points. I have zero experience with metal roofs or removing earth piled on frame construction floors.
1. In nj and not too many metal roofs. Ones I see have fairly steep slopes. Usual metal roofs go on in pieces therefore full of open seams. I am conditioned by my area to worry about such roofing on flat to little slope roof.
If metal roof, I would assume that the roof will be rebuilt with truss to give proper slope.


2. I think you asked a roofer, so got roofer's answer about removing the earth. I'm not saying the roofer is wrong, but he may not have the experience or the equipment. Example, a garage floors where a car can be parked have been built, although they didn't last long. Your earth roof should have been built with that weight in mind, so I think it's worth exploring if hand driven excavators or such can be used on your roof system. Even if you have to lay down plywood sheets for a "road". Should at least save some time. If calculating, lots of safety margin.
Your assumption is the same as what I'm understanding to use a metal roof, a small truss system is built to establish a pitch of 2/12, then place a seamless metal roof (I think a little more $$$, but can withstand a slighter slope than metal with seams.) Most of the people who have come out want to establish a slope of around 2/12 and put something like TPO up there, so if the slope is the same either way, I'd choose the more permanent(?) metal.

This is where I ask the question of contractors, if I'm getting a truss system installed is it THAT much more expensive to build higher up and establish more usable space since either design requires a wooden truss system? I think the answer is - depends if the current structure can withstand the current weight. I should know more this week when I hear back from the general contractor.

1 of the roofers who came out was ready to bring a full-size Bobcat out to excavate. Since I have leaking and am unsure about weak spots up there, I voiced hesitation and he said he could hand dig it, or use a hand-operated bobcat instead. The ones who want to do it all by hand seem to have the mantra "better safe than sorry".

I do have 1 more random question -- the pond liner is apparently quite robust, only breaking down from UV light. What are people's thoughts on doing wedge foam, overlaying with pond liner (or TPO) and maybe a drainage mat, then covering that with artificial turf? That'd have some curb appeal, and would seemingly protect the waterproof layer from the sun, extending the lifespan?? It'd look like a green roof, without the same headaches (excavation) of dealing with leaks someday
 
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