Advice On How To Use Waterproofing Construction Sealants
Posted: Sunday, February 01, 2009
by Christos Strogilis
http://www.macon.gr
JOINTS WATERPROOFING: TIPS
1) Select the sealant wisely. Use the criteria mentioned in previous entries. There are numerous problems and each of them calls for the most appropriate solution. In case of doubt you should consult an expert.
Wrong selection will cause great inconvenience and unreasonably high cost for reparations.
2) If you need maximum resistance to aging, go for MS Polymers.
3) Choose a sealant with low elasticity modulus when:
- substrates are brittle, friable or powdery
- considerable expansion contraction is expected
- fast expansion construction cycles are expected.
4) No sealant can accommodate widths over 40mm. You will have to use special joint waterproofing profiles.
5) You don't have always to use the most expensive solutions. Cheaper products may be fine for certain applications.
6) Avoid summer or winter when you apply sealants. Always prefer fall or spring. Stresses will be considerably lower.
7) Sealants should move as freely as possible. They should adhere only to the two opposite main surfaces. Use bond breaker or backer rod. Bonding to three sides will induce very high stresses and possibly failure.
8) Check the proportions between width and depth.
As a general rule:
* minimum dimensions should be 6mm x 6mm
* for joint widths between 6-12mm depth should be slightly less than width
* for joint widths between 12-25mm change the depth progressively from 8-12mm
* for wider joints keep the golden rule: depth = of width.
More is not always better. So use the backer rod to regulate depth. A big depth besides sealant wastage will lead to excessively high stress and increase possibilities for adhesive failure. A big depth will not guarantee a better waterproofing result.
9) Remember that mold resistant silicones have a certain functional life. After 10 years at the most they will need replacement.
10) When monocomponent sealants polymerizing with moisture delay to harden, check the following causes:
- product has expired
- there is no accessibility to air
- temperatures are low
- relative humidity is very low.
WATERPROOFING WITH SEALANTS: MORE TIPS
1) The diameter of backer rod should be wider than max width of the joint.
2) Definetely use a primer when:
- joint will be subject to hydrostatic pressure
- substrate surface is crumbly, friable or dusting.
Correct application of primer is of paramount importance. Respect consumption rates and time spans.
3) Two component systems must be thoroughly mixed with no apparent streaks.
4) Allow for the shrinkage of certain sealants.
5) Perform finishing before sealant creates a skin. You can use special tools or your finger occasionally immersed in soapy water.
6) Sealants are produced with different viscosities. For horizontal joints you can use self leveling products whereas for vertical/inclined joint thixotropic sealants are advisible.
7) Adhesion loss is maybe the most common cause of failure.
Pay attention :
- Select the right product.
- Clean the substrate minutely. Check it's integrity.
- Use the idoneous primer.
- Press firmly to ensure full contact and optimum wetting.
8) Adhesive failures of sealants are mainly due to:
- not adequately cleaned/prepared substrates
- weathered sealants
- inadequate depth
- bad choice of sealant of primer.
9) Cohesive failures of sealants are mainly due to:
- poor tear resistance
- weathered sealants
- extreme stresses due to three-sided adhesion.
10) Usual points, however elastic, will normally crack on the sealant region. An aesthetic problem will be almost inevitable while waterproofing capacity will not be impaired.
11) The most probable reasons for sealants failure are the following:
- bad joint design (e.g. inadequate width)
- very wide adhesion front
- unfortunate choice of sealant
- insufficient substrate preparation
- three-sided adhesion.
Take all the above points in consideration and you will achieve a long lasting waterproofing of the joint.
Chris Strogilis
http://maconwaterproofing.blogspot.com/
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