If the moss is buried it is unlikely to regrow. But you need to think about why that area was mossy in the first place. If it is shady, damp and compacted you need to change those conditions or moss will just come back.

I've no idea what an eco lawn is. Can you outline your vision? And I'm rather confused as to to how buried timber caused flooding.

I will agree with floral that burying the moss is sufficient to kill what currently exists so no need to treat again. Moss is actually very easy to get rid of - just raking well will dislodge and kill most of it - but unless you address the conditions that fostered its growth, it will return. Even in very healthy lawns, moss is pretty much a fact of life here in the PNW. The good news is that the conditions you need to seed a new lawn will address most of these. My biggest concerns would be compaction/poor drainage and lack of soil fertility. I am also finding a disconnect between the buried timbers and flooding so suspect that improper grading and compaction are more to blame.....those would be my areas of priority.

And I'd take the advice about liming with a large grain of salt. It is not a requirement at all unless your soil tests below a 5.5 pH!! Most turf grasses prefer a slight acidic pH to grow well (as do the vast majority of other plants) and that includes the fescue-type grasses that are common to an ecolawn. It is also unusual for a PNW soil to test much below 6.0 - most will be in the 6.3-6.5 range. Applying lime may be totally unnecessary and just an added step/expense that can be avoided.

And it is important to understand that the ecolawn will be summer dormant in our area unless it is routinely watered in summer.

I would PAY to have a moss lawn instead of other stuff that has to be mowed. So beautiful and soft, and moss wouldn't waste our time or $ with noisy mowing. It sounds like you are working to create more work for yourself.

In this tiny world, moss is the star of the show.

http://www.mossandstonegardens.com/blog/about/fbcover/

Thanks so much to all who answered. Can't believe I totally overlooked getting back to you! Argh.

So yeah, the moss is gone! So far. But as most mentioned, I understand now that it is preventing the conditions for its regrowth that is important.

@floral_uk: it was indeed shady, compacted, and wet.

To address the shade: I bought a pole trimmer, researched pruning cuts, and cut out a ton of overgrowth in my huge holly tree that was basically shading the entire back lawn. That enabled me to install a lawn (deep shade, mind you) as opposed to groundcover like ajuga or something. So it's still shady, but I have enough sun for a specialized lawn.

To address the compaction: I dug out as much clay as possible--it looked like you could make pottery out of it, seriously--and got rid of it. Like maybe 100 lbs of it. Bought about 100 cu ft of compost and topsoil, and integrated that (along with some grit and finer gravel the former tenant left in the yard) with Tuface (a true miracle! so glad I found it). It's a ceramic soil conditioner that has many of the benefits of perlite and the like, but doesn't break down immediately. It's typically quite expensive, but I found it fairly affordably at my local lawn store, Pro-Time Lawn. I highly recommend it; as I was turning over the soil, was amazed at the difference in how the heavily treated areas were so much more workable than those that I had not used as much on.

I also added a bit of lime: we have very acidic soil in Portland, but mine wasn't off the charts. Like a 5 pound bag for 300 sq ft. I had read that any calcium (e.g., gypsum if you're not trying to change the pH) can be helpful in compacted, heavy clay situations. And lawn naturally likes a less acidic soil.

I'm seriously considering adding earthworm cocoons and possibly mycorrhizal inoculum to get the fairly shoddy soil going and aerated.

Which brings me to your question regarding ecolawns: check out the Pro Time Lawn site for details. Very interesting mixes. Lucky to be in Oregon, where a lot of turfgrass is grown. Basically, an eco-lawn is made up of non-traditional blends, designed to suit the planting area rather than forcing the soil to accept a traditional lawn--anything from meadows to microclover to a mix, like their Rough & Ready (creeping and sheep fescues combined with ryegrass for rapid growth) with additional poa trivialis for my shady, seasonably wet conditions.

@gardengal48: you are familiar with eco-lawns, and can see if you look at the links that this isn't a "true" one--it has a blend of creeping and sheep fescues combined with ryegrass for rapid growth and micro-clover. Hoping to have something approaching a lawn at least my dog can walk on in 6 weeks as per the seed company, but we'll see. But you're right, it'll take a year to get it fully established (cross your fingers for me!).

To address the wet: This is really the toughie. Like, seriously, going to have to research this. In Portland, it might not rain at all for weeks on end in the summer, but it's a constant drip drip drip from October to March. And since I rent, and am on a tight budget, I don't want to invest a ton in drainage systems. But it is clear that something needs to be done. Right now I'm leaning toward creating a swale lined with landscaping fabric and gravel that will lead to a rain garden with some sort of overflow, but the clay soil combined with the layout of the yard makes it difficult. I did my best to regrade sloping away from the house, but unfortunately, my landlord hasn't done the best with the gutters and it would be ideal to have the rain garden near the house--which is a no no per the City. So I need to figure this out before the fall.

And btw @purpleinopp: I agree with you on moss being great--it's just apparently pretty expensive to get started (if you want to establish it in less than 3 years). You have to pick one or the other, more or less--moss or lawn. Both just doesn't work well IMO.

So again, thanks all for everything, and sorry for the REALLY late reply. I'm having so much fun gardening (except that my hands are killing me argh)!

I think moss gardens are cool. The Japanese have refined it to a high art. I wouldn,t be out every day raking it with a toothbrush like they do over there though.