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Sleeping without a tent, and the figures that decide which route

Leaving the tent behind means choosing between a bag that wraps you and a sheet that covers you. Each has its own specification sheet, and each has one figure that decides whether the night works — the breathability number on a bivy, the tie-out count on a tarp.

There are two ways to sleep out without a tent, and they fail differently.

A bivy bag puts a waterproof layer directly on your sleeping bag. It packs small, it needs no pitch, and every bit of moisture you produce has to leave through that layer or stay inside it. A tarp puts a sheet in the air above you. It is airy and versatile, it needs trees or poles and something to tie to, and it leaves your sides open to whatever the wind is doing.

Read the specification sheets and the difference is immediate: bivy listings publish waterproofing and breathability, tarp listings publish cut sizes and what is in the bag.

The bivy figure that most listings skip

A water column is easy to publish and easy to understand. A breathability figure is neither, and it is the one that decides whether you wake up in a damp sleeping bag.

The MFH hooped bivy publishes both: a 10,000 mm water column and 3,000 mvp, from a three-layer laminate whose face fabric is not named. It also publishes a pitched size of 235 x 70 tapering to 95 cm with 45 cm of height, six ground attachment loops, mat loops for mats up to 60 cm wide, a side and head opening on a two-way zip, an integrated mosquito net, about 1.4 kg and a packed size of 35 x 13 x 13 cm. On this shelf that is close to a complete specification, and it is why it opens the list.

The normani cover publishes the same pair — 10,000 mm and 3,000 MVP — on a Diamond Ripstop polyamide, with welded seams, a right-hand zip, a 230 x 90 cm cut and a stated 397 g. It is the light option here, and it is a cover for a sleeping bag rather than a shelter of its own: no pole, no hoop.

The Carinthia takes the other route. It names its material in full — three-layer Gore-Tex, polyamide face, PTFE membrane, polyamide lining — and publishes no water column and no breathability figure at all. What it does publish is size: 243 cm long with a 98 cm shoulder, which is a cut made for a bulky winter bag. The membrane name is what is being bought here, and the numbers are not on the page.

The GEERTOP is a different object again: a one-person shelter with two aluminium poles, a PU 5000 mm flysheet, fully sealed and double-stitched seams, 215 x 75 cm with 61 cm of head room, 45 x 13 x 13 cm packed, and approximately 1.3 kg stated for the complete set — labelled as the whole set rather than the canopy alone, which almost nothing else on this site troubles to say.

Where each bivy stops

None of these bivies publishes a denier. The Carinthia and the GEERTOP publish no breathability figure. The Carinthia publishes no weight and no packed size, so the two questions a walker asks first cannot be answered before it arrives.

That is worth knowing rather than resenting. A listing that names a membrane and gives you a 243 cm cut is telling you it expects the buyer to already know the model, and it is being straightforward about which half of the picture it offers.

The tarp figures that matter, in order

A tarp is a simpler object and its listings are correspondingly more honest, because there is less to hide.

The Unigear is the one to read first, for a reason that has nothing to do with the fabric: it publishes a tie-out count, and it publishes it size by size. Eight loops on the 3 x 3 m, eighteen on the 3 x 4 m, nineteen on the 3 x 5 m, sixteen on the 4.4 x 4.4 m. Attachment points are what let one sheet become a lean-to, an A-frame, a flying diamond or a porch, and a tarp with eight of them and a tarp with nineteen are not the same tool. It also publishes a PU 3000 mm water column, a 210D Oxford weave with a silver coating inside, and a bag containing six adjustable nylon guylines of 4 m, six aluminium pegs and a separate pouch for them, packing to 30 x 17 x 10 cm.

The FREE SOLDIER publishes the other half of the argument: a 300 x 300 cm square in 150T ripstop polyester, seam-sealed, with every load point reinforced with multiply-stitched nylon webbing stated to spread the load across the strap. Reinforcement is where a tarp tears, and a listing that describes the stitching at the load points is describing the failure it has thought about. It states 1 kg, and does not say whether the four ropes and four pegs are inside that figure. Its water resistance is published as a 3000 PU coating, with the figure given without a unit.

Reading a tarp’s cut size

A tarp does not have a floor, so its cut size is doing the work of both a footprint and a roof. Square sheets — the 300 x 300 cm on both tarps here — pitch in the most configurations. Rectangles favour one long axis, which suits a hammock or a two-person lean-to.

Fabric is published unevenly. The Unigear gives a denier — 210D Oxford — while the FREE SOLDIER gives 150T, which is a thread count and not the same measurement at all. Reading one against the other is reading two different quantities.

Which route to take

Take the bivy if the pitch is unknown, the trees are absent, and the priority is packing small and lying down anywhere. Then buy on the breathability figure, and if there is not one, buy knowing there is not one.

Take the tarp if there are trees or poles, if you want to cook and sit under cover, and if you would rather have air moving than fabric on your bag. Then buy on the tie-out count and on what is in the bag, because a canopy without lines and pegs is a half-purchase.

And take both if the trip is long: a tarp overhead and a light cover on the sleeping bag is the combination that handles a night of rain and a night of dew without carrying a tent for either.

Where the water actually gets in

A water column describes a fabric. A seam is where that fabric ends, and it is where water gets in first — so the seam line deserves the same reading as the millimetres. The GEERTOP states fully sealed seams with double stitching, the normani states welded seams, and the FREE SOLDIER states waterproof treatment at the seams. The MFH and the Carinthia publish a fabric and say nothing about what holds it together.

What we would carry, and why

  1. MFH Hooped Bivy with poles, 10,000 mm stated

    Hooped bivy · poles supplied · 3-layer laminate · 10,000 mm water column · 3,000 mvp · mosquito net · 1.4 kg and 35 × 13 × 13 cm packed, stated

    The one hooped bivy here with poles in the box — it publishes a water column, a breathability number and six ground loops, and names no test for the number.

    Best for: A one-person pitch where the head space of a hoop is wanted and a tent is not.

    ≈ 75 €

  2. normani bivy sleeping bag cover, 10,000 mm stated

    Sleeping-bag cover · Diamond Ripstop polyamide · 10,000 mm water column · 3,000 MVP · welded seams · right-hand zip · 397 g stated

    The listing in this hub that publishes both numbers: a 10,000 mm water column and a 3,000 MVP breathability figure — with no test named for the second.

    Best for: A sleeping bag that needs a light, fully specified waterproof cover rather than a shelter of its own.

    ≈ 40 €

  3. GEERTOP Ultralight 1-person bivy shelter, PU 5000 mm

    One-person bivy shelter · two aluminium poles · PU 5000 mm flysheet · sealed and double-stitched seams · 215 × 75 × 61 cm · 1.3 kg complete, stated

    A poled one-person shelter sold as a bivy, publishing a flysheet water column, sealed seams and a complete-set weight — with no fabric named and no breathability figure.

    Best for: A solo pitch where head room and a sealed floor matter more than packing small.

    ≈ 83 €

  4. Carinthia Sleeping Bag Cover, 3-layer Gore-Tex

    Sleeping-bag cover · 3-layer Gore-Tex · polyamide face and lining, PTFE membrane · 243 cm long, 98 cm shoulder · central zip · no weight or packed size

    A 3-layer Gore-Tex cover that names every layer of its construction and publishes neither a waterproof figure, a breathability figure, a weight nor a packed size.

    Best for: A winter sleeping bag that needs a long, wide cover and where the membrane name is the specification being bought.

    ≈ 535 €

  5. Unigear Rain Fly tarp, 210D Oxford, PU 3000 mm

    Camping tarp · 210D Oxford, silver-coated inside · PU 3000 mm · tie-out count published per size · six guylines and six alloy pegs supplied · 30 × 17 × 10 cm packed

    The only tarp here to publish a denier, a hydrostatic head and a tie-out count for every size it sells — and it never says which size the listing is showing.

    Best for: A first tarp bought complete, where lines and pegs in the box matter as much as the canopy.

    ≈ $25 / 30 €

  6. FREE SOLDIER tarp 300 × 300 cm, 150T ripstop, 3000 PU

    Camping tarp · 300 × 300 cm · 150T ripstop polyester, 3000 PU coating · seam-sealed · webbing-reinforced load points · 1 kg stated · four ropes and four pegs supplied

    A 3 × 3 m tarp with a coating figure, sealed seams, webbing at every load point and a stated 1 kg — and no count for the load points it reinforces.

    Best for: A square tarp bought complete, where sealed seams and reinforced load points matter more than pack weight.

    ≈ £44 / 38 €

What people ask before buying

Why does breathability matter more on a bivy than on a tent?

Because the fabric is against your sleeping bag rather than an arm's length away, so moisture that cannot get out condenses where it does the most harm. The MFH publishes 3,000 mvp and the normani publishes 3,000 MVP; the Carinthia names Gore-Tex without a figure, and several bivy listings make no breathability claim at all.

What is a tie-out count and why does a tarp listing hide it?

It is the number of attachment points, and it sets how many pitches the sheet can take. The Unigear publishes it size by size: 8 loops on the 3 x 3 m, 18 on the 3 x 4 m, 19 on the 3 x 5 m and 16 on the 4.4 x 4.4 m. Most tarp listings publish none.

Does a bivy replace a mat?

No. A bivy bag is a shell over a sleeping bag; the ground insulation still comes from a mat underneath, and the MFH is explicit about it with mat loops for mats up to 60 cm wide.

Which of these needs poles, lines and pegs bought separately?

The GEERTOP comes with its own two-pole frame. The Unigear ships with six 4 m guylines and six aluminium pegs, and the FREE SOLDIER with four ropes and four pegs. The flat covers and the plain bivy sacks come with nothing.

Prices in these summaries were read on the dates each review gives. The live figure sits beside every product.

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