Joints and bay sizes
A bay is the area poured as one piece between joints. Liquid screeds allow much bigger bays than sand and cement, but the limits differ a lot by product: 300 m² heated and 1,000 m² unheated for calcium sulphate, and 40 to 100 m² heated and 80 to 150 m² unheated for cement-based.
Every product also needs a joint over any structural movement joint, between separately controlled heating zones, and where heated and unheated screed meet.
Free, no obligation. One local screeding contractor prices it, not five.
The limits
| Calcium sulphate | Cement-based liquid screed | Cement-based liquid screed | |
|---|---|---|---|
| Heated bay | 300 m², 20 m long | 40 m² | 100 m² |
| Unheated bay | 1,000 m², 40 m long | 80 m² | 150 m² |
| Longest side | 20 m heated, 40 m unheated | 8 m | Not given |
| Aspect ratio | 8:1 unheated, 6:1 heated | Not given | Not given |
| Perimeter strip | 8 mm, 10 mm with heating | At all walls and columns | Not given |
Where joints go
- Over every structural movement joint in the slab below.
- Between independent heating zones, and between heated and unheated screed.
- At door thresholds on heated floors.
- In corridors where they change direction, and where an L-shaped room's corner points outward.
- Where a bay would go over the area or length limit.
How they're formed
There are two ways. Preformed 8 or 10 mm closed-cell foam strips on a self-adhesive T base go down on the membrane before the pour and are trimmed flush after; this suits heated floors because nothing is cut. Or saw cuts at 2 to 3 days, half the screed's depth and at least 5 mm wide, filled with flexible epoxy. Avoid those over underfloor heating. On cement-based, rigid joint formers go in during preparation, set about 5 mm below the finished level.
For trade jobs where bays drive the programme, see screeding.ie on commercial floors.
Liquid screed poured by the contractor who takes your call
Calls on this site ring JAM Floor Screeding: James Mulhall, based in Portlaoise, 25 years laying floors. Lines open Mon to Sat, 7am to 6pm. These are his jobs.
“JAM were punctual, professional and efficient and did an outstanding job on pouring our new floor as part of a renovation. Very highly recommend!”
“Excellent work, laser level finish, neat and tidy worker, highly recommend.”
“Top class work by james and his crew, highly recommend”
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Joints and bays questions
How big can a liquid screed bay be?
Calcium sulphate: 300 m² heated, 1,000 m² unheated. Cement-based liquid screed: 40 m² heated, 80 m² unheated. Cement-based liquid screed: 100 m² and 150 m².
Does liquid screed need expansion joints?
Yes, over structural joints, between heating zones, between heated and unheated areas, and where a bay passes the maker's size limit.
Can joints be sawn into liquid screed?
Saw cuts at 2 to 3 days, half the depth, at least 5 mm wide, but not over underfloor heating: use preformed joints there.
What width of perimeter strip for liquid screed?
At least 8 mm, or 10 mm with underfloor heating: closed-cell polyethylene with a polythene skirt.
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