EFFICIENT waterproofing of roofs and terraces can be achieved by adopting proper construction practices. For a tropical region with heavy rainfall, (like Mumbai or places on the west coast), a ‘Weathering Course’ typically consists of an insulating layer with an integral or separate finishing layer of IPS; and a waterproofing course suitably laid directly over the R C slab. It is essential that no rainwater stagnates on the roof. This can be achieved by a proper slope and adequate number of drainage outlets. The requisite slope is obtained by varying the thickness of the insulating layer, Or when the roof slab is large in area, the slope is often provided by making its (the slab) top surface sloping to the desired extent.


NEW TERRACES:

When it is intended to carry out the waterproofing of a newly built reinforced concrete roof, it is best to provide the waterproofing layer directly on the structural slab. The insulation layer and the finishing layer can then follow.

To obtain a sound waterproofing layer:

Ø Clean the surface of all loose particles, dust, cement laitance etc. preferably done using a electric hand blower.

Ø Moisten the R. C. slab and on the wetted surface, apply three coats of POLYALK-WP and Cement slurry in the ratio 1:1.25 by weight for first coat and 1:1.5 by weight for subsequent coats at 24 hours interval between each coats. The slurry should be uniform in consistency and suitable for brush application.

Ø Cure the first two coats with damp gunny bags after 48 hrs of the application of the above slurry.

Ø Apply the third coat of POLYALK WP and while this coat is still wet and tacky lay the mortar for providing brick bat coba. This has to be a wet on wet application.

Ø Provide insulation layer (brick-bat coba) and finish layer (I.P.S.) over the coating as per requirement.

Ø Admix anti-shrinkage compound SUNPLEX (330gms pouch) per bag of cement for the mortar mixes of brick bat coba and I.P.S

Note:
In case the roof is a sloping one, then the POLYALK WP – Cement Slurry can be applied over the top of the slab and provide only the Finish layer.


EXISTING TERRACES :

Often there is a need to repair an existing terrace or roof due to seepage of rainwater through them on account of failure of the insulation layer or the finishing layer or both. While doing so it is necessary to inspect the existing terrace and judge the reasons of failure of existing water proofing system which is provide.

Generally the leakages may be due to –

(a)  Account of the failure of the IPS or China Mosaic.
(b) The cracking and failure of the brick bat coba.
(c)  The failure of both.


For case (a):

Ø Remove the existing I.P.S. or china mosaic chips layer over the slab.

Ø Clean the insulation layer (brick bar bat coba) by removing all loose particles.

Ø Provide a lean cement-sand leveling and smoothing course less than 10 mm thick.

Ø After the above layer has hardened say after 24 to 48 hours; prepare and apply three coats of a lump free, consistent slurry of POLYALK WP and cement in the proportion 1:1.25 (by wt.) for first coat and 1:1.5 by weight for subsequent two coats at 24 hours interval between each coats.

Ø Cure the first two coats with damp gunny bags after 48 hrs of the application of the above slurry.

Ø Apply the third coat of POLYALK WP and while this coat is still wet and tacky lay the mortar for providing finish layer (I.P.S.). This has to be a wet on wet application.

Ø Provide finish layer (I.P.S.) over the coating as per requirement.

Ø Admix anti-shrinkage compound SUNPLEX (330 gms pouch) per bag of cement for the mortar mix of I.P.S.


For case (b) & (c) follow steps given below:

Ø Remove the finish layer (I.P.S.) & insulation layer (brick bat coba) to expose the R.C. slab.

Ø Clean the slab and inspect for cracks and defects.

Ø Preparation of the surface to be waterproofed is of utmost importance. Cracks other than hairline on the RCC slab should be widened freed from loose particles and then filled with a mortar consisting of ‘POLYALK EP’, fresh cement and quartz sand in the proportion of 2:5:15 by weight, without adding water. This mortar should be prepared in limited quantities and utilized within 30 minutes.

Ø Prepare and apply a lump free, consistent slurry of POLYALK WP and cement on the bare and cleaned R.C.C. slab in the proportion 1:1.25 (by wt.) for first coat and 1:1.5 by weight for subsequent two coats at 24 hours interval between each coats.

Ø Cure the first two coats with damp gunny bags after 48 hrs of the application of the above slurry.

Ø Apply the third coat of POLYALK WP and while this coat is still wet and tacky lay the mortar for providing brick bat coba. This has to be a wet on wet application.

Ø Finish the surface by doing brick bat coba and I.P.S. as per the requirement.


Ø Admix anti-shrinkage compound SUNPLEX (330gms pouch) per bag of cement for the mortar mixes of brick bat coba and I.P.S.