False Ceiling And Cement Floor Advice

[Jillsounder 1]

Hi all,

Just want to check if its normal for false ceiling to have crack lines and cement screeded floor that my contractor told me it uses a kind of chemical different from the normal cement to crack just 20 days after renovation has been completed? The cementing of my floor area cost about $6000 for about 400sqft...Any advise will be greatly appreciated.

[Leonster 0]

Hey Jill,

Good day to you

Just wanted to check with you on a few things:-

(i) Would your place be a HDB ? Cause I do understand that HDB is able to do the cementing of the floor for free.

You'll need to go to the nearest HDB branch office and fill up a form. They'll then make arrangements for it to be done.

(ii) I take it that you are going for an industrial feel thus the cement screeding, however from what my contractor told me and from experience from my other friends. there will be cracks over time but NOT to the extent of just 20 days after the renovation. There are a number of causes of cracks in screeds, such as hydrometric shrinkage, too much water in the mix, the use of aggregates which are too fine or too much cement. Do note that before installing flooring, all cracks must be monolithically sealed by filling them with epoxy resin such as EPORIP or EPOJET.

The choice of which type of aggregate to use is important. It must be clean, contain no impurities and have the correct grain size for the thickness of the screed to be laid. If the aggregate are too fine, more mixing water will be required and the surface porosity of the screed will be reduced. As a result, drying time for the mortar will be longer and there is a higher risk of shrinkage cracks

Refer to the following link : http://www.mapei.com/public/IT/linedocument/QT_MASSETTI%20GB.pdf for further information

I dont mean to say this but i think your contractor did not do a good job and he definitely overcharged you. My house total area is 94 sq m and that is around 1011 sq feet . I did cement screeding for my living room,walkway and bedroom and total cost was 1,600 ( i know the rates varies with contractor but 6k is ridiculous)

(iii) I think the general rule applies, if you are not happy with a service rendered, make sure you complain to the contractor and get it fixed.

With regards to your false ceiling, it should not have any cracks as its just bee newly renovated yeah.

p.s: Remember to take picture of the contractor's shoddy work as evidence

[Leonster 0]

Jill,

Just further information for you.

Refer to the following link : http://www.adhf.co.uk/html/body_screed_faq.html ( this is taken from a UK site)

Q11. I’ve heard about shrinkage cracking & curling in floor screeds, what are these and how do they occur?

A. Any material that has absorbed water, will shrink as it dries out. Sometimes, due to excessive drying, screeds will crack.

If you try to artificially accelerate the drying times, of the table above, then there is more risk of cracking.

Curling is caused by the same conditions but normally manifest along dayjoints and internal angles.

The thinner the screeding material, to be used, the more likely that curling can occur, due to time taken to dry will be quicker on a thinner bed, than a thicker bed.

Another way to reduce shrinkage & cracking is to use water-reducing agents (super-plasticisers), these are used in Truscreed and K-screed and greatly reduce drying times.

Q.15 We have a screed that is weak, cracking, or badly dusting. Is it necessary to replace the screed?

A. No, but sometimes it may be the most commercially viable option. There are products that can be applied that will remove these problems, these are not cheap, but it may be the most viable option when you consider the cost of removal of the old screed and the cost of replacement. For example PHS could be applied, and the following day it would be possible to apply floor finishes, including vinyl, as there would be no drying times to consider.

And you may refer to this site as well http://www.concrete.org.uk/fingertips_nuggets.asp?cmd=display&id=672

Question on screed durability

What has caused my sand cement screed to break-up?

Answer

There are two aspects; is failure due to cracking or crumbling?

Crumbling is caused by a lack of compaction or low cement content. A screed tester (in accordance with BS 8204) is likely to show that the screed falls short of the lowest Category C (indentation of 5 mm). An analysis to assess the proportion of sand to cement might indicate a low cement content. Visual inspection and density check of the screed may suggest poor compaction.

Cracking is expected in all sand cement screeds (Clause 6.9.1 BS 8204) unless sufficient joints are provided. Cracks are not considered a problem under thin floorings e.g. vinyl sheet/tiles or carpet, unless the screed has curled at the crack. See clause 8.4 in BS 8204-1

The general recommendation would be that unsound areas of screed should be cut out and replaced. Proprietary systems can be used to upgrade an unsound screed, which may be by impregnation with a low viscosity resin or by laying a fibre-reinforced, flowing cementitious screed. Trials of repair systems should be undertaken using test methods such as the BRE Screed tester.

If the overall quality of the existing screed is found to be similar to the areas tested, it may prove more cost effective to remove and replace.

[Leonster 0]

Hope this helps =)

[Leonster 0]

With regards to your cracks in your False Ceiling, I was only able to locate the following information, get your contractor to redo it.

There should not be any cracks in your newly done up false ceiling.

Ceiling cracks happen naturally over time as a result of many factors. The older a structure is, the more likely that stress, moisture, and temperature will cause the formation of cracks. Several other factors, however, can accelerate effect of wear and tear. Poor workmanship is the most common cause of early ceiling cracks, specifically if inferior technique was involved in building the ceiling.

Other external factors, such as accidents and forces of nature, can also lead to the formation of ceiling cracks.

All materials used in construction wear down over time. Plaster, wood, and other materials will crack under stress and pressure that's accumulated over time. This is especially true if the ceiling in question has another floor or attic above it. A large amount of force coming from the upper floor can be enough to cause ceiling cracks over the lower one. As a rule of thumb, the thicker the flooring, the sturdier the lower-floor ceiling is and the less likely it is for ceiling cracks to form

Temperature and moisture fluctuations can also lead to ceiling cracks. Materials expand when moist or warm and contract when cool. If changes in either heat or temperature happen sporadically, as in monsoon seasons in tropical climates, this can lead to undue internal stress in the ceiling materials, causing a crack in the ceiling. In most cases, the crack is formed in the thinner layer of paint on the ceiling's surface, although cracks in the plaster itself are also possible.

[chriswoo23 0]

Hi Leonster, can share your contact for the floor contractor? Thanks