Screeds 3

[phuduhudu]

I came across advice recently that it is difficult to achieve a well adhering screed with the dry screeding method. However, here, every builder uses that method and not the wet screed method. The other piece of advice I saw was that the screed should not be floated off woth additional cement. Again this is common practice here. Anyone got any ideas on the best practical way to do a screed on a concrete floor slab for domestic construction. Carl Bauer

http://www.bauerconsultbotswana.com

 

[emmgjld]

My best advice is that you do whatever works.

The wet screeding method is supposably superior, unless the contractors do not want to. I know that sounds a little ridiculous but, I have to assume that the local talent does what has worked in the past, given the materials and products available. Sometimes the old habits are hard to break and sometimes the old habits are there for a very good reason.

I had opportunity(?) to be in Viet Nam many years ago and I found the practices to be a little amusing until I got to understand the limitations. Just a couple of years ago, I was in Belize, building a church, and was confronted with practices almost identical to Viet Nam of 30 years ago. I know that the belize construction methods are limited to smaller, up to 3 story structures and light traffic on the slabs. It works and until the construction is pushed beyond the existing norm, there is probably no reason to change.

The floating or dusting of the wet slab surface with cement is not a good pratice. HOWEVER, I have observed dusting being accomplished in a manner, with the appropriate final slab finishing and curing, which resulted in an acceptable final product. Again, my prior experience in Viet nam and Belize was instructive.

I believe that these 'bad practices' can oftentimes be accomplished in a manner which results in an acceptable final product. The key is proper training of the finishers for the 'normal' products and that a 'normal' FINAL DESIRED USAGE is desired. When products, mixes, and/or FINAL USAGE change, then these practices will probably not be acceptable and the resulting customer complaints will assist in convincing the contractors of 'better' ways.

If you are now dealing with the problems of changing the final usage or an increase in the clients expectations, you have my sympathies. I listened when my father waxed elegant on the subjects in the '50s and '60s and then I moved to 'rural' areas and confronted the same problems in the '70s and '80s and I am still dealing with it.

 

[Riz]

Carl,
Dry screeding is good in tropics. Its done widely here in Tanzania where the contractor wants to ensure the rapid drying of the matrix does not create hairline/fine cracks. The floating is done with cement slurry. Dry screeding can be carried out expeditiously too.