How Many Roof Layers Will Building Support?

It is time for a new flat rubber roof on our co-op building. Should we be concerned about how many layers of old roofing material are up there? If we take a ‘core sample’ and determine for example that we have two inches of material down already, are there any rules of thumb as to what depth of roffing material should concern us? Also, we hope to put a roof deck up there after the new roof is installed. Should the deck construction be “modular” in case we have to move it for future roof repairs? What should we put on the legs of the deck to protect the roof? Many thanks….

ejalbk

in Roofers 13 years and 4 months ago

4

Please log in, in order to post replies!

4 replies

Newest Oldest

jockdeboeraia | 13 years and 4 months ago

string(1) "1"
object(WP_User)#4850 (8) {
  ["data"]=>
  object(stdClass)#4893 (12) {
    ["ID"]=>
    string(5) "40876"
    ["user_login"]=>
    string(13) "jockdeboeraia"
    ["user_pass"]=>
    string(34) "$P$BTfkV3DGGseot8oNyuG6kVhsNhUD2n1"
    ["user_nicename"]=>
    string(13) "jockdeboeraia"
    ["user_email"]=>
    string(22) "jdeboer@jockdeboer.com"
    ["user_url"]=>
    string(31) "/forums/users/deboerarchitects/"
    ["user_registered"]=>
    string(19) "2017-08-10 14:15:51"
    ["user_activation_key"]=>
    string(20) "VK4zWrfWbTPHLfSSlGZI"
    ["user_status"]=>
    string(1) "0"
    ["display_name"]=>
    string(13) "jockdeboeraia"
    ["spam"]=>
    string(1) "0"
    ["deleted"]=>
    string(1) "0"
  }
  ["ID"]=>
  int(40876)
  ["caps"]=>
  array(2) {
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["cap_key"]=>
  string(15) "wp_capabilities"
  ["roles"]=>
  array(2) {
    [0]=>
    string(10) "subscriber"
    [1]=>
    string(15) "bbp_participant"
  }
  ["allcaps"]=>
  array(4) {
    ["read"]=>
    bool(true)
    ["level_0"]=>
    bool(true)
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["filter"]=>
  NULL
  ["site_id":"WP_User":private]=>
  int(1)
}

3 layers is allowed, but to know the max you would need to look at the existing joists and what that could support.  If it was my roof, I would strip it each time.

jcarch | 13 years and 4 months ago

string(1) "1"
object(WP_User)#4851 (8) {
  ["data"]=>
  object(stdClass)#4852 (12) {
    ["ID"]=>
    string(5) "23991"
    ["user_login"]=>
    string(6) "jcarch"
    ["user_pass"]=>
    string(34) "$P$BS0hz8fYZfWVNwJxAdb5D7GSB6JTfb."
    ["user_nicename"]=>
    string(6) "jcarch"
    ["user_email"]=>
    string(22) "jpc@jcarchitecture.com"
    ["user_url"]=>
    string(21) "/forums/users/jcarch/"
    ["user_registered"]=>
    string(19) "2017-08-10 14:06:39"
    ["user_activation_key"]=>
    string(0) ""
    ["user_status"]=>
    string(1) "0"
    ["display_name"]=>
    string(6) "jcarch"
    ["spam"]=>
    string(1) "0"
    ["deleted"]=>
    string(1) "0"
  }
  ["ID"]=>
  int(23991)
  ["caps"]=>
  array(2) {
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["cap_key"]=>
  string(15) "wp_capabilities"
  ["roles"]=>
  array(2) {
    [0]=>
    string(10) "subscriber"
    [1]=>
    string(15) "bbp_participant"
  }
  ["allcaps"]=>
  array(4) {
    ["read"]=>
    bool(true)
    ["level_0"]=>
    bool(true)
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["filter"]=>
  NULL
  ["site_id":"WP_User":private]=>
  int(1)
}

As mentioned by bhs, the real issue is that w/ more layers, you get moisture trapped in between the layers…a lot of moisture.  I was on a roof in mid-summer (it hadn’t rained in a couple of weeks), and when the contractor took up the multiple layers on a roof, is was sopping wet.  Over time that means damage to the roof structure. For a deck, I’ve done several of these.  It should absolutely be modular.  If there’s a leak someday, you don’t want to have to demolish the deck before you can fix it.  It’s also very unlikely that the roof structure can handle the added dead/live loads of the deck.  Roofs were/are designed to meet roof loads, not floor loads which are greater.  And older buildings were designed to meet lower loading too.  So you want to have an architect/engineer check this.  It’s 99% likely the existing structure won’t do the job, so you’d then have to put in steel beams from parapet to parapet (or something similar), and have the deck bear on the new steel.

kidbklyn | 13 years and 4 months ago

string(1) "1"
object(WP_User)#4855 (8) {
  ["data"]=>
  object(stdClass)#4849 (12) {
    ["ID"]=>
    string(5) "12959"
    ["user_login"]=>
    string(8) "kidbklyn"
    ["user_pass"]=>
    string(34) "$P$BALKN6lQMZUcIMychkXehk8I4wSPr01"
    ["user_nicename"]=>
    string(8) "kidbklyn"
    ["user_email"]=>
    string(15) "bkny648@aol.com"
    ["user_url"]=>
    string(23) "/forums/users/kidbklyn/"
    ["user_registered"]=>
    string(19) "2017-08-10 14:16:51"
    ["user_activation_key"]=>
    string(0) ""
    ["user_status"]=>
    string(1) "0"
    ["display_name"]=>
    string(8) "kidbklyn"
    ["spam"]=>
    string(1) "0"
    ["deleted"]=>
    string(1) "0"
  }
  ["ID"]=>
  int(12959)
  ["caps"]=>
  array(2) {
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["cap_key"]=>
  string(15) "wp_capabilities"
  ["roles"]=>
  array(2) {
    [0]=>
    string(10) "subscriber"
    [1]=>
    string(15) "bbp_participant"
  }
  ["allcaps"]=>
  array(4) {
    ["read"]=>
    bool(true)
    ["level_0"]=>
    bool(true)
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["filter"]=>
  NULL
  ["site_id":"WP_User":private]=>
  int(1)
}

I believe that 3 layers is the maximum you can have on a sloped roof. Flat roofs don’t have that restriction. Call a legit roofer like Premier Roofing and ask them.

BHS | 13 years and 4 months ago

string(1) "1"
object(WP_User)#4850 (8) {
  ["data"]=>
  object(stdClass)#4848 (12) {
    ["ID"]=>
    string(5) "11181"
    ["user_login"]=>
    string(3) "BHS"
    ["user_pass"]=>
    string(0) ""
    ["user_nicename"]=>
    string(3) "bhs"
    ["user_email"]=>
    string(20) "smythraina@gmail.com"
    ["user_url"]=>
    string(18) "/forums/users/bhs/"
    ["user_registered"]=>
    string(19) "2017-08-10 14:14:48"
    ["user_activation_key"]=>
    string(0) ""
    ["user_status"]=>
    string(1) "0"
    ["display_name"]=>
    string(3) "BHS"
    ["spam"]=>
    string(1) "0"
    ["deleted"]=>
    string(1) "0"
  }
  ["ID"]=>
  int(11181)
  ["caps"]=>
  array(2) {
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["cap_key"]=>
  string(15) "wp_capabilities"
  ["roles"]=>
  array(2) {
    [0]=>
    string(10) "subscriber"
    [1]=>
    string(15) "bbp_participant"
  }
  ["allcaps"]=>
  array(4) {
    ["read"]=>
    bool(true)
    ["level_0"]=>
    bool(true)
    ["subscriber"]=>
    bool(true)
    ["bbp_participant"]=>
    bool(true)
  }
  ["filter"]=>
  NULL
  ["site_id":"WP_User":private]=>
  int(1)
}

In addition to the weight, I think you should be also concerned about whether there are bubbles or sections that can’t be made totally flat. Areas where water pools, even if they aren’t large can lead to leaks even on a newish roof, and the water that pools can itself be quite heavy. I think my house inspector mentioned 3 layers max, but I don’t recall 100%.