Prefabricated Concrete House Roof Waterproofing

Waterproofing for the roof of a prefabricated concrete house requires comprehensive control from three aspects: material selection, construction techniques, and regulatory requirements. Specific measures are as follows:

I. Material Selection

1. Polymer-modified cement-based waterproof coating (JS-II type): With a solid content ≥65%, tensile strength ≥1.8MPa, and elongation at break ≥80%, it is suitable for roof base treatment, effectively filling minor cracks in the base layer and enhancing the flexibility of the waterproof layer.
2. Self-adhesive polymer-modified bitumen waterproof membrane (1.5mm thick): Featuring a polyester base, tensile force ≥400N/50mm, elongation at maximum tensile force ≥30%, and impermeability of 0.3MPa/30min without leakage, it is used for large-scale roof铺设 (laying). Its self-adhesive properties simplify the construction process while ensuring strong adhesion.
3. Cement-based capillary crystalline waterproof coating (Type D): With a compressive strength ≥12MPa, waterproof pressure resistance ≥0.8MPa, and penetration depth ≥40mm, it is suitable for areas prone to leakage, such as joints between prefabricated components and pipe roots. It achieves long-term waterproofing by closing capillary pores through a crystalline reaction.

II. Construction Techniques and Key Points

1. Surface Cleaning: After installing the prefabricated roof panels, remove dust, debris, and repair differences in panel joint heights to ensure a flat base layer, preventing the waterproof layer from cracking due to base layer defects.
2. Leveling Layer Construction: Use a 1:3 cement mortar (mixed with 5% waterproofing agent) with a thickness of 20mm. The surface flatness error should be ≤5mm/2m to provide uniform support for the waterproof layer.
3. Node Reinforcement: At nodes such as gutters, eaves, water outlets, and pipe roots, first apply a 1.5mm thick layer of JS-II type waterproof coating and lay a non-woven fabric reinforcement layer to enhance local crack resistance.
4. Membrane Laying: Self-adhesive membranes should overlap by 80mm on the long side and 100mm on the short side. Lay them from the lowest point of the roof towards the higher points, overlapping in the direction of water flow to prevent rainwater backflow.
5. Hot-melt Edge Sealing: Use a torch to hot-melt weld the membrane overlaps, ensuring the edges are firmly fused. Excess bitumen should be scraped flat and compacted to prevent water seepage.
6. Edge Treatment: After trimming the membrane edges, secure them with metal strips (spaced 500mm apart) and seal with sealant to prevent rainwater from infiltrating along the edges.
7. Drainage Slope Setting: Set the drainage slope according to design requirements. Additional drainage channels can be installed to guide rainwater to drainage outlets, preventing water accumulation on the roof.

III. Relevant Regulatory Requirements

Roof waterproofing projects must comply with the mandatory standards of the General Code for Waterproofing of Buildings and Municipal Engineering: For flat roofs with a Class II waterproofing requirement, there should be no fewer than two waterproofing layers, including at least one membrane waterproofing layer, to ensure the reliability of the waterproofing system.