Polyurethane Log: Selection and Installation Guide
Choosing the log section by ceiling height, working out quantities and installing in seven steps — end caps and wood-effect paint included.
Two decisions determine the result of a polyurethane log installation: choosing the right section and fixing the log chemically and mechanically at the same time. If the section does not follow ceiling height the run looks either crushed or lost; if only adhesive is trusted, joints open over time with thermal movement. This guide covers seven steps from sizing to wood-effect paint.
Required Materials and Tools
• Fine-tooth hand saw or mitre saw
• PU-based mounting adhesive (NOT silicone)
• Screws of suitable length and a cordless driver
• Laser level or chalk line
• Acrylic filler
• 180-220 grit abrasive
• Topcoat plus patina for the wood effect
• Damp cloth
• Trestle or scaffolding for height
Step-by-Step Application
- Set the section and axis spacing — Section is proportional to ceiling height: 100×100 mm reads well on a 2.60-2.80 m ceiling, 200×250 mm above 3.20 m. Axis spacing is five to eight times the section, so the logs look neither crowded nor scattered.
- Work out the quantity — Divide the short side of the ceiling by the axis spacing for the number of runs, and the long side by the 3 metre bar length for pieces per run. Add about 10% waste for cutting. Add an end cap for every run end and a bracket wherever the log meets a wall.
- Mark the axes — Mark the axis lines on the ceiling with a laser or chalk line. The run follows the direction of windows or beams; setting it perpendicular to the long axis of the room makes the space look wider.
- Cut — Use a fine-tooth hand saw or a mitre saw; the material is too dense for a utility knife. Use 45° mitres at butt joints and corners. Filling a bad cut produces cracking and paint loss.
- Bond and cross-screw — Apply the PU-based mounting adhesive in an uninterrupted bead to the face against the ceiling and to the joints (silicone is forbidden). Press the part home, then cross-screw at top, middle and bottom, sinking the screw heads into the material. Wipe squeeze-out with a damp cloth before it cures. Curing takes about one hour in normal conditions.
- Fit end caps and brackets — Bond an end cap of the same section to every cut end; an open end reveals the hollow profile. Place a bracket where the log meets the wall: it closes the junction and gives a load-bearing impression.
- Fill, sand and paint the wood effect — Fill screw heads and joints flush with acrylic filler, sand with 180-220 grit once dry and lightly mat the whole surface. The wood effect comes in two stages: a base colour as the topcoat, then a dark patina worked into the grain. The primer must be the system primer of the topcoat brand. Outdoors the topcoat must be elastic and UV resistant.
Section and axis table by ceiling height
The table below matches the nine available sections to ceiling height. Axis spacing may change with the design; these values are a starting point for a balanced look.
| Ceiling height | Suggested section | Axis spacing | Note |
|---|---|---|---|
| 2.40 - 2.60 m | 50×50 / 80×80 mm | 60 - 80 cm | Slim run; does not crush a low ceiling |
| 2.60 - 2.80 m | 100×100 / 120×120 mm | 80 - 100 cm | The most common room size |
| 2.80 - 3.20 m | 150×306 / 200×200 mm | 100 - 120 cm | Living rooms and large spaces |
| 3.20 m and above | 200×250 / 255×260 mm | 120 - 150 cm | Restaurants, hotels, loft spaces |
| Wall / niche | 80×80 - 120×120 mm | per design | Horizontal accent, end cap stays visible |
Log, beam or rafter: which product are you looking for?
A log is close to square and imitates a solid tree trunk (100×100, 200×200). A beam is wide and flat (350×320, 200×125) and reads as a structural member. A rafter is slim and tall (75×157), set closely along a roof pitch. They belong to the same product family and are listed together in catalogues; the proportion of the section is enough to tell them apart.
Common mistakes
Installing with adhesive alone lets thermal movement open the joints. Skipping adhesive on the joint has the same effect. Omitting end caps leaves the hollow section visible. Skipping or spot-applying primer causes peeling or tonal differences. Include the product weight and fixing loads when assessing the substrate and supporting structure.
Frequently Asked Questions
Which section should I choose?
By ceiling height: 50×50 or 80×80 mm at 2.40-2.60 m, 100×100 or 120×120 mm at 2.60-2.80 m, 150×306 or 200×200 mm at 2.80-3.20 m, and 200×250 or 255×260 mm above 3.20 m.
What axis spacing should be used between logs?
About five to eight times the section: 80-100 cm for a 100×100 mm log and 100-120 cm for a 200×200 mm log give a balanced look.
How many logs are needed?
Divide the short side of the ceiling by the axis spacing for the number of runs and the long side by the 3 metre length for pieces per run, then add about 10% waste for cutting.
Is adhesive alone enough?
No. Adhesive and screws are used together; cross-screwing prevents joints opening with thermal movement. Silicone-based adhesive is never used.
How is the log end closed?
With an end cap produced in the same size as the section, and with a bracket where the log meets the wall.
How is the wood appearance achieved?
The texture comes from the mould. The base colour comes from the topcoat and the depth from a dark patina worked into the grain. The primer must be the system primer of the topcoat brand.
Can a chandelier or other load be hung from a log?
It should not be. Include the product weight and fixing loads when assessing the substrate and supporting structure.
What is the longest single log piece that can be produced?
One uninterrupted piece runs to 3000 mm; longer runs are formed by butt-jointing in line. Position those joints where an interruption already reads — a wall line, a crossing beam, a ceiling break — instead of mid-span, then fill and sand before painting. Stagger the joints between neighbouring logs so they do not line up across the ceiling.
How much extra length should be ordered for cutting losses?
Allow 10% on plain profiles and 15% on patterned ones, because patterned faces must be cut so the grain continues across the joint. Angled cuts at hips, valleys and wall junctions consume more than square ends, so count those junctions when setting the allowance. Order the full quantity in one go — a later top-up is treated as a new order with its own lead time.
Can logs be applied to a sloped or vaulted ceiling?
On a pitched ceiling they follow the slope and are cut to the wall angle at each end; on a barrel vault the curvature has to be built into the piece during production, not forced on site. Take the true sloping length rather than the plan length, otherwise the quantity comes out short. Mechanical fastening matters more here than on a flat ceiling, because gravity pulls along the adhesive line instead of into it.