My Flat roof project-help!

johnk

Also,in your first pic,first post,is that a dormer on the right?Just wondering

federer

the proposal makes no mention of a base sheet though =/
what do you suggest for a mid ply? is that what grumpy meant about putting down a layer of the smooth mod bit?

the mod bit is going on the flat section, not the rear low sloped. so you are saying no i&w for the mod bit section.

federer

not sure which you mean-in the first pic its the neighbors house in the background. to the right is the rear side of the house. it's original. its the front flat slope thats added on. but both front and back were finished. so there is no real attic space. which is a pain

Grumpy

Ice shield under a mod bit is ridiculious!

First layer should be a fiberglass reinforced base sheet, something like a CertainTeed glass base or Firestone's equivelent. I usually doulbe up my base also called half lapping where we install the 3' roll with an 18" exposure. The base sheets are most often mechanically fastened using metal button cap nails or screws and plates.

A mid ply would be the firestone app 160. It is a smooth modified bitumen about 4mm thick. This is torch applied, welded, to the base sheet.

Finally the cap sheet would be the firestone app 180, a granulated modified bitumen about 4/5mm thick. This is torch applied to the mid ply.

The above system rating when properly installed is 20 years.

Keep in mind before the plys are installed I would also installa 1/2" high density fiberboard. I never want to be torching to a wood deck, this is also why we double up the base sheet. Furthermore I only do modified bitumen on request, and most often on a small reisdential project like this I would be using a self adhering modified bitumen. First layer is nailed or screwed as described above. With the self adhering, we can negate the fiberboard. The 2nd layer is a self adhering mid ply, and the final layer is a granulated self adhering cap sheet.


Your proposal makes absolutely no metnion of fiberboard and or base sheet. I pray for your sake they do not intend to torch directly to the wood. Aluminum drip edge on a torch applied roof?! the aluminum will wrinkle and buckle from the heat. better to get a Kynar steel when installing a torch applied product. The steel can be prefinished just like aluminum can and with the Kynar coating, will last 25 years.

I'm not sure this roofer has a clue, in my opinion.

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-Grumpy

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Sometimes the savings that comes from doing it yourself can be blown away with one mistake.

The information found in this post is not to be considered legal advice. All information should be considered relative, not specific. Never attempt any repairs you are not comfortable with. Always maintain safety! The author of this post takes no responsibility for any losses that occur. Use at your own risk.

federer

thanks so much grumpy! this is real bad because we decided they were the best to go with. now i have to go back and amend the proposal. thanks so much for the suggestions-yea they mentioned no base sheet,etc. so i should ask for a fiberglass base sheet, and self adhering plys so i dont need fiberboard on the bottom? or should i get get fiberboard and have it torched it down for each ply? their proposal only said " The installation of Firestone #180 modified bitumen 12-year roofing material on flat roof. All material fastened per manufacturers requirements." so i dont know if its self adhering or not!

OldNBroken

Nothing self-adhering belongs in any torchdown spec.
Like Grumpy said, at minimum they should nail a base sheet, then apply the torchdown over that.

federer

thanks OldNBroken- so base sheet, mid ply, then cap with the granular 180. how much would it add to the cost by putting the smooth mid ply? $500?

johnk

There are self-adhering base sheets out there,that are meant for torchdown.These can replace nailed base and are considered a ply.http://www.google.co.uk/search?hl=&q...oprema+colvent There is one example,here is another iko fast and stick.They do cost a little more,but well worth it.I usually use a hot air welder for endlaps.Sorry for the late reply Federer,I have been a little busy.

OOPS!!Here is the link this time http://www.google.co.uk/search?hl=&q...CA344&ie=UTF-8.

Lets try again http://www.iko.com/products/commerci...al_region_id=3. Finally!

federer

thanks john-no problem i understand people get busy etc so apparently the roofer did not write it in on the proposal because he says its a 'given that a base sheet will be installed in any torch down roof'. he doesnt want people asking so many questions...so thats that. he also says a mid ply is not necesary. apparently firestone only warrants commercial jobs too. so i only have their warranty to go on.

federer

so reading through this
http://www.buildingscience.com/docum...earchterm=roof

should i go with the spray foam under the deck unvented, or rigid board on top of the decking??? so much headache =/

Grumpy

Firestone makes a self adhering torch applied base sheet, it's like a very thin smooth modified bitumen. Certainteed also makes a self adhering torch applied base sheet called black diamond.

If I were putting modified on my house I would most likely install a fiberboard over the wood, double layer of glass base over the fiber board, smooth torch modified and granulated torch cap with all accessories previously mentioned.

The smooth mid ply woudl add much more than $500 in my opinion. 500 would be materials. What about labor profit and overhead?


As for insulation? What do you have now? If your ceiling is currently insulated with fiberglass, then my recomendation is to remove some deck boards and improve the existing fiberglass. Then I would install roof vents. This is called a cold deck design because the roof deck is ventilated instead of insulated.

If you have no insulation in the ceiling, then you could either insulate the ceiling or insulate the roof deck. Do not do both.

__________________
-Grumpy

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Sometimes the savings that comes from doing it yourself can be blown away with one mistake.

The information found in this post is not to be considered legal advice. All information should be considered relative, not specific. Never attempt any repairs you are not comfortable with. Always maintain safety! The author of this post takes no responsibility for any losses that occur. Use at your own risk.

hereslookingatU

Hi!

Not sure how far you've gone down the road of recovering your roof, if knowhere then do a web search on 'liquid plastics' this is a wet process where fibreglass matting is either bonded over the existing roof covering or PIR or Polystyrene insulation is bonded and fixed to the existing roof covering and the liquid plastic applied over the top.

That's it in simple terms, you should find the detailed information on the web search.


Regards

federer

thanks so much for the input grumpy! yea currently there is some fiberglass batts i think. one bid is to add r38 blown in fiberglass for $2k. i guess thats my best option? its way cheaper than spray foam too.

for the roof the contractor keeps insisting that i just need a base sheet and the cap =/ so i dont know what to say.

rodeo

IMO, in a cold clime, insulating above the deck with ISO boards is FAR superior to sprayfoam below the deck/between rafters.
Sprayfoam is best used in situations where starting over, (ie: reroofing) is not an option.

Many contractors view a thick layer of ISO board above the deck as cutting into their profit margin or they might strip out large areas of that ISO as a shortcut to facilitate drainage. Thats how my new flat roof got botched.

federer

thanks for the comment. can you please tell me more? how did your new roof get botched? becase of the lack of iso boards under the roof?