building-regulationsroofuk
We bought a new house last year. Going up to the loft we noticed there is a considerable gap (5-6 cm) between the roof and the wall, like this:
Is it supposed to be like that?
It's freezing up there but I'm more concerned about animals entering the house.
I'm a contractor in Maine and we certainly have a lot of experience with ice dams. An ice dam can be the quickest way to force water under the roof shingles even on a roof in good shape.
I have had mixed results with heat tapes. When they are used properly, they can be somewhat effective. Most folks expect to see a nice bare zig zag pattern along the edge of the roof with the ice gone around the tape. Not how it works!
If you carefully read all the directions on many of the competing brand heat tapes out there, you will see that they do not claim to remove ice dams. They are designed only to create a small open tunnel under the ice dam to allow water that is trapped above the dam to drain off the roof. This is great in theory but here is where the reality sets in. If the tape does not extend slightly beyond or below the drip edge of the roof, it won't work. If the top edge of the tape does not extend above the ice dam, they will not work. If the gutters fill with ice and bridge the ice to the roof, they won't work.
Many of the tapes instruct you to only operate them when outdoor temps are 30 degrees and above. I have found that they are ineffective in temps much below 20 degrees. They also caution not to let them run continuously.
Running them in the bottom of a gutter is almost a complete waste of time and money. Since they only are capable of melting a small area around the tape, a gutter full of ice will stay full of ice! If the downspout is blocked with ice, forget it!
What I have also found is that folks get a false sense of security when they have them installed and neglect to remove the snow from the bottom 3 to 6 feet of their roofs, figuring the tape is a substitute for roof shoveling. Obviously, when they are installed, shoveling or using a roof rake gets a little tricky, so as not to rip the tape right off the roof.
I guess you can tell I am not a fan of these heat tapes. One method I have found to be extremely effective with dealing with an ice damn are nylon stockings or pantyhose (cut into two sections) filled with salt, calcium chloride or potassium chloride placed over the dam. They last several days and melt slowly and make a nice wide valley in the ice. I have seen hundreds of gallons of water pour off from behind an ice dam using them. Chopping the ice dam can damage the shingles and can be dangerous, but the filled stockings are fairly quick and easy.
If you have plants below or are concerned about salt staining your roof or siding etc, I highly recommend Potassium Chloride which will not harm plants, grass etc. You can usually find potassium chloride at your local hardware store.
I can't take credit for discovering this method, but thankfully I learned it from a tip on This Old House many years ago. I usually make up dozens of them in advance, so I am ready for all the calls from folks who wait too long and call to see if I can come fix the water leaking through their ceilings!
What they are suggesting is done in metal buildings in the USA, the insulation is wrapped in a type of plastic sheeting on all sides, it is made that way. It is also in large rolls and very wide, maybe 3-4ft?
My biggest concern would be the distortion of the metal when it comes to removing it. If the roof is attached with screws, you have a small chance of salvaging the roofing. If the roof is fastened with nails, the metal will surely be distorted. The fasteners to reattach the roofing, which should be screws with neoprene washers, rely on a flat surface, if it is a newer system. The refastening may not take well if care is not taken on the removal. Of all the fasteners in any given roof it will only take one to create leak, with the insulation in place and it's plastic layer, it would be hard to tell where a leak may really be or if any evidence is visible until it is too late. I refer to wet, or rotted framing after a time.
If it is the older system where the nails are driven through the standing rib, and the nail has a lead coating to conform and seal the hole from the nail,, DO NOT let them remove it unless a new roof goes back down. It may be better to insulate from the underside, even if it may be finished.
This is a sample of what I was going to suggest, It may cost more overall, but it is the metal roof and insulation combined. It will not compress like the fiberglass will and give a higher R rating
Best Answer
There needs to be air circulation in unheated space to prevent condensation causing rot.
That is good. It means your loft insulation is working.
I found fixing wire-mesh externally to any small gaps at the top of the walls keeps unwelcome types of animal out. You could instead apply this internally.
The Royal Society for the Protection of Birds encourage builders to make provision so that critters can enter your roof to nest.
Note the wire-mesh guard to prevent them getting to areas where they would be unwelcome.