We recently got spray polyurethane (PU) treatment for our house in Islamabad. The results are dramatic.
I know of at least three firms that provide spray PU services in Pakistan. One operates exclusively in Karachi/Hyderabad and with their add appearing regularly in the daily DAWN. The other two are Master Chemicals (manufacturers of Moltyfoam) and Diamond Industries (manufacturers of Diamond foam). They offer this service in Punjab and N.W.F.P also and their contact info for Rwp/Isb is as follows:
Master Chemicals (Pvt.) Ltd.
Tel: 051-2279816, 051-2271175
Tel: (051) 111-111-666
Cell: (0333) 5600393
There may be others but I am not aware of them.
Basically the process consists of two liquid chemicals that are kept separate till the last moment before spraying their mixture at a pressure of 110 psi. The chemicals immediately react and the semisolid goo turns solid within 10-15 seconds. The resulting compound sticks to anything and also flows into and fill all the cracks (thereby helping to water proof the roof as an added benefit). They said the treatment has no life limit and should last the lifetime of the building. However, it is degraded by the UV radiation of the sun and needs protection from that. Therefore it needs to be covered up by either concrete screeding (for regular foot traffic) or a special UV paint or an elastomeric coating (for minimal foot traffic). Both can be arranged by the same people who do the spray PU treatment. In our case we went for Master ThermoShield. It cost Rs. 32/sq ft for the basic spray PU and a further Rs. 17/Sq ft for the elastomeric coating. The UV paint option was available for Rs. 12/sq ft though.
One more thing and I got this from Master (so may include business prejudice). They said only they use German material (BASF) while Diamond uses Chinese material (ICI China).
The spray PU treatment may not be an option for those living in rented accommodation. In such a case, just paint the top of your roof a bright white. This will reflect the radiant energy of the sun away. However simple this may sound, believe me it’s extremely effective. The only down side is the relatively short life requiring repainting more frequently. You can use from plain simple limestone (dirt cheap but gone with the first shower) to limestone+POP (more durable but messy) to paint (plastic emulsion will cost Rs. 8-10/sq ft but will stay on for a couple of years). Results are dramatic nonetheless.
Finally a word for those building their house. At the first opportunity, plant saplings of tall growing trees on the south side because that is where the sun will always cast it's shine during summer (applies to northern hemisphere only). Also consider PU injection of your outer walls in addition to spray for roof. Treating the walls require hollow wall construction whereby the outer walls are constructed as double walls leaving a one inch gap in between. The PU is then pressure injected into the cavity through a hole that is later sealed off with concrete. PU treatment during construction is not only cheaper but wall treatment will keep you warmer in winters too and help reduce your energy costs/carbon footprint.