Screeds – Extension & Renovation Project
What screed should be used?
With radiators insulation is less important. For underfloor heating insulation in the floor is a major issue. For this extension and renovated floors 125mm of Kingspan or equivalent will be used.
There are three main screed types.
1. Traditionally semi dry sand cement was used. Easy to lay and every screed layer has a pump to handle it. But, for underfloor heating it gives poor contact around the pipes. It may crack.
2. Modern liquid screeds are being heavily promoted. The advantages are
• fast release of heat
• faster drying times
• easy to install accurately
• suitable at 50-60mm depth
There are two main types.
a. Hemihydrate floor screeds when dried out are ready to receive tiles.
b. Anhydrite based screeds will need surface scum removed before sticking down tiles or other flooring materials.
3. The third screed type is sand / cement / stone – concrete. This is strong and provides great thermal mass. The disadvantages of concrete are that it is difficult to install level and the normal screed pumps will not pump it. After consulting with the screeder I hope to engage we will be trying a new method of installation.
The quality of the build and the primary heat source influence the most suitable screed for a particular project. If a house is leaking heat a liquid screed gives a quick delivery of heat. However, in a well insulated “tight” house (house with a high degree of airtightness) and big thermal mass a slow delivery of heat may be more appropriate. The other factor is primary heat source. Using oil, biomass or gas the energy cost is the same 24 hours per day. Using electricity through a heat pump requires Economy 7 to be effective. The energy price before 7am is significantly reduced.
In this project heat will be from an air to water heat pump. The screed will be concrete. We hope to prove the new method of getting the concrete level.
For further information contact Eric Davidson 0772 912 5002