| Fully bonded |
Fully bonded screeds need to be laid on a shot-blasted / scabbled concrete base, and be bonded using an adhesive such as PVA, SBR, epoxy resin or good old fashioned cement. |
| Partially bonded |
Partially bonded screeds are a cheap alternative to doing the job properly, and have the added risk of the floor screed failing, because at depths less that 50mm, the screed can start to break up if the bond to the concrete is lost. This system is only used when people are trying to save money, and sometimes bonding agents like PVA & SBR are still used, but they are still at high risk from failing due to the slab not being shot-blasted or scabbled. |
| Unbonded |
Unbonded Screeds as the name suggest are not bonded directly to the concrete base, but are intentionally debonded with the use of a DPM (damp-proof membrane). The advantage is that any cracking from the sub-base is not carried through to the screed, drying times can be reduced by omitting the concrete drying time. All walls and pillars must be lined with edging foam or 20mm insulation, such as Kingspan, to protect against shrinkage cracking. |
| Floating. |
Floating Screeds are laid on insulation to provide an insulated floor area. All walls and pillars must be lined with edging foam or 20mm insulation, such as kingspan, to protect against shrinkage cracking. This system is the most commonly used in house building, especially with underfloor heating systems. There is very little difference between unbounded and floating screeds. high-impact insulation such as extruded polystyrene can give the same levels of rigidness on floating screeds as you would expect from unbonded screeds |
