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built-up roofing
Built up roofs are the oldest form of Bituminous Roofing membranes. They are constructed of lapped asphalt-impregnated (cellulose, glass, or synthetic) felt installed by hot-mopping coal tar pitch (level or very low slope) or liquid asphalt product which adhere to eachother to forma durable, multi-ply roofing layer.
![1.jpg](https://static.wixstatic.com/media/bae38a_e4bce40c6a954db1996c1f745bc6752f~mv2.jpg/v1/fill/w_600,h_338,al_c,q_80,usm_0.66_1.00_0.01,enc_auto/1.jpg)
![2.jpg](https://static.wixstatic.com/media/bae38a_368bbd2e94d1476fabaab5e71d135895~mv2_d_3648_2736_s_4_2.jpg/v1/fill/w_99,h_74,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/2.jpg)
An underlayment may be necessary and/or required by local building code and is often perlite, gypsum board, or tongue and groove wood.
![2a.png](https://static.wixstatic.com/media/bae38a_93af08de1fdb4b389a4e4aed1d75ee94~mv2.png/v1/fill/w_60,h_29,al_c,q_85,usm_0.66_1.00_0.01,blur_2,enc_auto/2a.png)
Also a vapor retarder may be necessary under the underlayment (or base sheet if no underlayment exists). They are commonly constructed of a base sheet of glass fiber typically lapped 2″ or a base roofing felt with 4″ laps. Then layers of the asphalt-impregnated ply-sheets (432SF or 216SF; 15 or 30lb rolls) are installed with 12″ then 24″ starter courses before applying the 36″ plies, with hot asphalt binder in between each ply. The mopping between felts typically requires 25-30 lbs per square. For 2-ply roofing, lap is typically 19″; 3-ply is 24-2/3″; and 4-ply is 27-1/2″. Finally a specialized/coated cap sheet is applied in rolls with the final coat of hot-mopped asphalt applied on top, often at a higher rate of 65-75lbs per square. Pipe boots for built-up-roofs are typically lead or copper and installed by the roofing contractor (except for non-MEP penetrations). Galvanized pipe boots will not adhere to asphalt membrane roofing.
![BUR.jpg](https://static.wixstatic.com/media/bae38a_42f02bc25ddf45adabfc6e5736195680~mv2.jpg/v1/fill/w_124,h_93,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/BUR.jpg)
![builtuproofing2_000.jpg](https://static.wixstatic.com/media/bae38a_706730f65db64e0485107959d12cfbc9~mv2.jpg/v1/fill/w_102,h_65,al_c,q_80,usm_0.66_1.00_0.01,blur_2,enc_auto/builtuproofing2_000.jpg)