What does ‘Hydrostatic Head’ mean?

Hydrostatic Head (HH) is a way of measuring how waterproof a piece of fabric is. The manufacturer will take a clear tube and clamp their material over the bottom end. They will then fill the tube slowly with water and watch to see how high the column of water can get before the material lets drips through. An HH rating of 2000mm means that the column of water was 2 metres tall before the material leaked.

In real-world terms, where you have wind and gravity pushing rain into a tent fabric you will need a measurement of around 1000mm to resist heavy showers. Heavy rain and driving wind will create more pressure on the fabric and require a higher number of around 2000mm. Anything above this (some tents are rated up to 10000mm) and your tent material should survive against water being pushed through by something physical and heavy, like a tree branch rubbing on it in the wind.

A ground sheet, where the pressure of you walking/sitting/laying is likely to be quite great, will ideally have a HH rating of 5000mm+. It should also ideally curve up at the edges to keep rain water from seeping over the top of it.

Don’t compare HH measurements for tents against those used for clothing, since clothing will rub on itself, your backpack and rough surfaces and therefore require a higher rating to resist that pressure.

What are Taped Seams?

When you take a nice piece of waterproof material and sew through it, you punch holes through the waterproofing. These holes need to be sealed up, and the easiest way to do that is for the manufacturer to apply a hot-melt tape over the seams of the tent. You can get an aftermarket seam sealer (McNett Seam Seal) if your tent develops any leaks.

Why is my 3-man tent so small?

Tent manufacturers tend to give measurements based on average-sized people laying down, perfectly still next to each other. A 2-man tent is probably not going to be sufficient for a long tour with backpacks for 2-men. A 3-man tent probably won’t fit 3 men, 3 backpacks, 3 pairs of smelly boots, a stove, some beer and a blow-up sheep. If you go tent shopping, get them to throw a couple of mattresses and a backpack in the tent with you and see how quickly the tent feels small.

Fire retardant! Great, can I cook in the tent?

No, you’ll either gas yourself, burn to death or spill your beans. Only ever cook in a porch unless you really know what you’re doing. Fire retardant does NOT mean fire proof.


  • linda

    Hi, I need help. I’m living in Cork Ireland and currently have a 5 man tent with a rating of 3000mm, I found it very damp and not very waterproof our trip last year. ive since had a new baby 5mth old and want to ensure our tent is very warm and waterproof. we have 3 kids and 2 adults. what is the most waterproof tent I can buy and the easiest to put up? is there such a thing?

    • Hi, and thanks for the query.
      Depending on your budget, and type of vehicle, we’d recommend you look at a canvas Bell tent such as those sold at https://www.belltent.co.uk/ (Possibly take advantage of the stronger Euro!). The space is good and cosy, and they breathe better than a synthetic tent for all the moisture created by families. You can, with some designs, even get a wood-burning stove to use in them if you want it super-toasty. They’re also really quick to put up so the kids won’t run off too far while you’re getting the centre pole up.

      If money IS an object, then have a look at the Outwell range of family tents. We think that they have a very slight edge over many rivals when it comes to ‘friendly’ features that could be helpful with a family. They have a big range to choose from.

      For what it’s worth, a 3000mm tent shouldn’t have leaked unless something was rubbing up against it, or it was defective in some way.