Tent waterproofing: materials and construction

HYDROSTATIC HEAD
The ability of a material to repel water is measured in terms of its hydrostatic head.  This is its theoretical ability to withstand the pressure of a column of water, measured in millimetres, without allowing any of it to penetrate. Virtually all tents sold in the UK will have a hydrostatic head measurement of at least 1,500mm, comfortably over the minimum 1,000mm that is required for it to be claimed as waterproof. A rating of 3,000mm or above should cope with any conditions you are ever likely to encounter but some will go as high as 6,000mm. In simple terms, the higher the HH rating the more waterproof your tent will be- although you still have to take into account other 'weak points' such as the seams (see below) and around the zips, where covers are essential to stop water getting in..

TAPED SEAMS
Most tents now have factory-taped seams, around which you may find a few pinprick holes. These won’t necessarily allow water to penetrate, but it is a good idea to use a seam sealant before first use. Remember to allow plenty of time for it to dry before packing the tent away again.

Any water seen clinging to the inside of the tent will almost certainly be condensation, which can be kept to a minimum by keeping the tent well aired. 

MATERIALS
Polyester was once regarded as a material most often found in budget tents, but it has now been elevated by being treated with various other materials to repel mildew and to make it resistant to UV light. Now most tents are made out of synthetic material.

Such has been the improvement in artificial materials that canvas is no longer commonly used, but recent years has seen a move back towards cotton and polycotton flysheets in some top-of-the-range tents.

Good quality fibreglass poles are fine, but beware of the cheapest ones, which will soon start to splinter after continued flexing.