422 DAMPPROOFING AND MEMBRANE WATERPROOFING
From MDOT Policy Manual
- Furnish and apply dampproofing and waterproofing to concrete surfaces.
Asphaltic Materials 913.01 Asphalt Primer 913.02 Fabric for Use with Asphalt 913.03 Membrane Waterproofing and Dampproofing 913.04
- Apply dampproofing and waterproofing using asphaltic materials, primers, and fabric; or by the roll or sheet method as specified in 422.03.07.
- 422.03.01 Storage. Store waterproofing fabrics and membranes in a dry protected place. Keep containers of asphalt materials closed when not in use.
- 422.03.02 Surface Preparation. Do not apply dampproofing or membrane waterproofing until curing is complete and surfaces are protected from the cold. Ensure that all surfaces are dry, smooth, and free from projections and holes.
- When dampproofing and membrane waterproofing are both specified for application, apply the membrane waterproofing first. Do not apply dampproofing or membrane waterproofing when the temperature is less than 40 F.
- 422.03.03 Dampproofing. If asphaltic coatings are used for dampproofing, use two prime coats and one seal coat. Apply dampproofing to the following concrete surfaces that will be in contact with backfill:
- (a) Rear face of abutments and abutment wing wall stems.
- (b) Rear faces of headwalls and wing walls for pipes 36 in. in diameter or larger and for culverts.
- (c) Rear face of retaining wall stems.
- (d) The following areas pertain to reinforced concrete box culverts:
- (1) Top of top slabs when not built to grade.
- (2) Entire outside surfaces of side walls.
- (3) Additionally, bottom of bottom slabs of precast units.
- 422.03.04 Waterproofing. If asphaltic coatings are used, use a prime coat, three mop coats, and two layers of fabric.
- Apply waterproofing to construction joints that are next to backfill above normal water surface when backfill is on one side and atmosphere on the other side. Apply a width of at least 16 in., centered on the joint.
- 422.03.05 Application of Dampproofing. Confine coatings to the areas to be covered. Prevent coating of parts of the structure exposed to view in the completed structure. Apply dampproofing to the full face of all contraction joints.
- Apply the dampproofing according to the manufacturer’s recommendations. When no recommendations are provided, apply the dampproofing material to the cured, cleaned, and dry surfaces as follows:
- (a) Paint with two coats of primer for absorptive treatment at a rate of 1/8 gal/yd2 per coat. Do not apply the second coat until the first coat has thoroughly dried. Do not heat this material.
- (b) After the second prime coat has thoroughly dried, apply one seal coat by brush or roller at a rate of 1/8 gal/yd2 . When necessary, this material may be heated, but not in excess of 150 F.
- 422.03.06 Application of Membrane Waterproofing. Coat the cured, cleaned, and dry surfaces with a prime coat. Cover with mop coats and layers of fabric.
- Coating Procedure. Coat with a primer at a rate of 1/8 gal/yd2 . Apply the prime coat 24 hours in advance of applying any mop coats and ensure that it is dry before applying the first mopping. Do not heat the primer.
- Heat asphalt for mop coats to a temperature between 300 and 350 F. Stir frequently to avoid local overheating. Provide heating kettles equipped with thermometers.
- Begin the waterproofing at the low point, so that water will run over and not against or along the laps.
- Make the first strip of fabric half width. Make the second full width, lapping the full width of the first sheet. Make the third and each succeeding strip thereafter full width and lapped so that there will be two layers of fabric at all points and three layers with laps not less than 2 in. wide at edges of strips. Make all laps at ends of strips at least 12 in. wide. Thoroughly seal down the cloth at all laps.
- Beginning at the low point, mop a section 20 in. wide for the full length of the surface with the hot asphalt. Immediately after the mopping, press the first strip of fabric into place eliminating all air bubbles. Mop this strip and an adjacent section of the surface to a width equal to slightly more than half the width of the fabric, and press a full strip and a full width of the fabric into place as before. Then mop the forward or upper half of this second strip and mop an adjacent section of the concrete surface with hot asphalt. Apply the third strip of fabric shingled on so as to lap the first strip at least 2 in. Continue this process until the entire surface is covered. Then give the entire surface a final mopping of hot asphalt. Ensure that there is a complete coating of asphalt between all layers of fabric.
- In all cases, ensure that the mopping on concrete covers the surface so that no gray spots are visible, and on cloth is sufficiently heavy to conceal the weave. Apply asphalt at the rates of 1.2 gal/yd2 on horizontal surfaces and 1.4 gal/yd2 on vertical surfaces. Regulate the work so that at the close of a day’s work, all cloth in place has received the coatings required for that stage of completion.
- 422.03.07 Roll or Sheet Waterproofing Membrane. An alternate system of waterproofing or dampproofing consisting of rolls or sheets of membrane material may be used in lieu of the above coatings. Apply the rolls or sheets according to the manufacturer’s recommendations.
- 422.03.08 Membrane Care. At the edges of the membrane and at points punctured by appurtenances such as drains or pipes, flash it in an acceptable manner to prevent water from getting between the waterproofing and the waterproofed surface. Repair any damage to the membrane. Extend repairs beyond the outermost damaged portion, and extend the second ply at least 3 in. beyond the first.
422.04 MEASUREMENT AND PAYMENT.
- Dampproofing and membrane waterproofing will not be measured but the cost will be incidental to other pertinent items specified.