A groundsheet is a relatively simple project. Getting the geometry right and sewing good quality seams is not as critical as with a tarp because there’ll be no tension applied and it won’t need to stand to any wind force. Just get the dimensions about right and sew away.

DIY TrailStar floor


I used 2.3 oz/sq yd, 70 denier silnylon. It’s an old batch of fabric I got in the early days of ultralight when 30 denier silnylon was still watched with caution. Back then I’d see a place for this heavier and thicker silnylon, particularly for groundsheets. It’s well known that 30 denier silnylon is not that waterproof when under pressure as it happens when you sit down or kneel with saturated ground on the other side.

I had run out of 30 denier silnylon and didn’t have time to order a new batch so decided to put the 70 denier to use. I had never used it so far, It’s the first item I sew out of it. I’ll see how it performs.

Raw fabric

The 70 denier silnylon feels thicker and sturdier than common 30 denier. It’s just as slick.

Measuring & Cutting

Measuring is always tricky for the DIY at home folk. It takes me some furniture removal to find real state but I found the perfect synergy by using said furniture as impromptu straight edge.

Find a long straight edge

The 70 denier silnylon came in a roll about 1.60 m wide. For this project, I cut two lengths, 190 cm long each that I later cut farther to shape, then joined alongside.

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Silnylon is very slippery, this makes it awkward to sew. My strategy has always been to use lots of pins. It’s tedious but every time I’ve tried using less or no pins, I’ve regretted it.

Lots of pins

This time I made quite a floppy job at sewing. My flat seams turned out a bit bulgy at times. Good seams may be critical for a fly but shouldn’t matter for a groundsheet.

The actual star in this story


The bathtub has no structure, it’s implemented by just folding inwards and sewing a short, vertical seam at every corner. It needs vertical support to stand up. The idea is to add a short line to the provided loop and hang from the matching attachment point in the TrailStar.

Bathtub wall

Specs summary

Fabric2 oz/sq yd, 70 denier Silnylon
Fabric length needed3.80 m
Work Time10 hours
Max Length1.66 m
Max Width2.54 m
Final Weight310 gr


Final weight is for the groundsheet alone, no lines or stakes considered.