I am planning to re-roof my garage using 2mm torch-on felt. The garage roof is about 19 feet long and only has a shallow gradient. Do I need to fit an underlay?

DO WHAT YOU WANT BECAUSE IF YOU ARE DOING IT YOURSELF AND ASKING QUESTIONS LIKE THIS IT IS BOUND TO FAIL ,WHY NOT GET A ROOFER TO QUOTE AS HE KNOWS WHAT HE IS DOING

If your going to do it properly you need 3no layers of felt, 2nd layer of underlay laid opposite to 1st. If using plain felt for 3rd layer you need solar reflective paint. Preffered 3rd layer green mineral. If you have never done torch on before, make sure you have a fire extinguisture close by, and have the relevant insurance for using naked flame. Far easier option use epdm.

Hi My answer to your question is first get in contact with a roofer,and ask for a free estimate.Laying felt is not as easy as it looks,to much heat applied and you can ruin the felt,to less heat and it will not stick.Never stick felt straight to boards,it will split at the joint,when boards move. I my self always use 1 layer of 3b base felt nailed 2 layer 2mm torch-on 3 layer 4mm mineral torch-on. Kind regards TRM Roofing & building.

If you need it doing properly; hire a fibreglasser and do it in GRP.

You will never get it water tight,seriously pay a professional & get it done right with a guarantee.

The 2mm layer will be your first of three layers. it should be torched down so that it runs into gutter. The 2nd layer of 2mm felt will run same way but u split the joints by half of the layer underneath....therefore u will now have laps every 18 inches. You should have a bead of bitumen exposed along lap when torching down, this is why you need someone that has used a gas gun before. 3rd layer to be in minerial and paint finish is out dated. Remember every layer of felt runs into the gutter and the laps are spoilt in half.

HI, Yes you will need to use a 2mm underlay tacked down then another 2mm stuck down and then a 4mm mineral torch-on .. if you want the job done properly . If not just tack a 2mm and then use a 4mm mineral torch-on .. Hope this helps :)

This is why Flat Roofing is getting a bad name. Please get a professional roofer in.

ideally 2 layers minimum, usually one 2mm and one layer of green or one 2mm and one layer of 4mm with solarflex Aluminum paint. Regards Dave

YES!!!!! and i strongly advise do not do this on your own it is not a diy job it will leak!

To be honest with you 2 mill felt is no good for it any way 4 MIL and a good underlay

yes