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chris

Roofing Felt

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OK, time for a topic on tips on roofing felt.

Possible discussion points...

  • How to fix it in place
  • Do you trim to the top, wrap round the side or wrap under the baseboard.
  • When two sections meet is it best to overlap or line them up flush.
  • With the benefit of hindsight...

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Looking at peoples galleries I can see a split between those of us who use widths of felt and those who use lengths.

I buy 8m long by 1m wide (10 year) felt. I unroll the whole thing and then cut strips long enough to cover the run of baseboard. And yes, I copied Ian. In working this way so far I only have one place where I've had to join the felt. Some of you have cut the roll across it's width to produce 1m lengths which then need a lot more joins. May way is a lot more cumbersome (getting 6m by 20cm of felt smooth ain't easy) but I'm scared of water ingress in joints. I'm hoping to be ready to lay some more felt in the next few weeks so feed back on the how all those joints have held up would be timely.

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Without any doubt I think it would be best to use long lengths with few joins rather than short lengths with many joins. If you've got a long straight section of baseboard then long lengths would be the way to go but for anything other than straight lengths there's no alternative but to apply the felt in shorter widths, especially if you need to economise on the quantity of felt used.

If the felt is applied correctly then I've found that butt joins are sufficient between sections of felt once they have been painted over with the bitumen to conceal the join itself. I tended to overlap adjoining sections and then cut through the two pieces together to make a flush joint. On areas where I have had to remove the roofing felt to remedy problems with the baseboard underneath, I don't recall any spot where water had found it's way beneath the felt.

I chose to wrap the felt around and over the sides in the knowledge that I could always trim it back later if required. I'm not sure of any advantages either way but it does protect the sides of the wood too rather than just the top surface.

In hindsight - I'd probably do much the same but in the knoweldege that it's important to make a good job of it. I'd like to think that next time there might be a better way altogether but we'll have to see.

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Well, having just put felt on my layout at the weekend, I can't speak for its longevity, but because my boards are 4 feet wide at the ends, I was faced with a choice between short joins or long joins and I felt ('scuse the pun!) that short joins would be easier to manage. Time might prove me to be wrong!

Also, whilst I use felt adhesive on the wood to stick it down, I also overlapped the felt by about two inches (the depth of the batons underneath at the edges) and used short (3/4") clout nails to secure it in place. I never thought about just applying the felt to the top and trimming to size. Perhaps because my only previous experience with roofing felt was on sheds, where I did it exactly the same as I've done on my layout.

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Uhm, I am going to sound really dumb. But what is this felt? Is it like the tar shingles we have here that are embedded with granules of stone?

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traingeekboy said:

Uhm, I am going to sound really dumb. But what is this felt? Is it like the tar shingles we have here that are embedded with granules of stone?

That sounds about right so they must be very similar. Over here it's available in rolls with one side coated in very fine stone granules and is used mainly as roofing material on garages, sheds, and other similar type outbuildings etc. as well as making a suitable base for outdoor model railways.

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Dave said:

Whilst I use felt adhesive on the wood to stick it down, I also overlapped the felt by about two inches (the depth of the batons underneath at the edges) and used short (3/4") clout nails to secure it in place. I never thought about just applying the felt to the top and trimming to size. Perhaps because my only previous experience with roofing felt was on sheds, where I did it exactly the same as I've done on my layout.

Dave, the stuff I did last year I used adhesive and trimmed to the edges. Earlier in the Summer I refeltted my shed and lipped it over, using a staple gun to tack it down.

The staple gun made the job super quick and it's a one-handed tool so I hand a hand free to pull the felt tight.

The trimmed edges look great, but they need extra maintenance so I'm going to try lapping the felt over the edge and stapling it in place.

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I never thought of using a staple gun, Chris. That's a good idea :)

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I purchased my staple gun when I needed to redo the shed roof. The original installers had used staples and they had coped far better than the felt :!: so I decided it was worth the investment of £5 to buy a gun.

The speed you can work at is amazing. On a recent evening I heard my neighbour hammering away for an hour or so, it was only the next day when I saw a new patch of felt on his shed that I realised what he had been doing. He'd have had the job done in ten minutes if I'd seen him at it and lent him the gun.

You can also produce very neat results with a staple gun, but only if you have a good staple removal tool as well.

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There is something very primal about clout nails, though. I rather enjoyed hammering them in at the time :)

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They do rust, but I've recently removed staples from a 12 year old shed roof and they were in better condition that the felt. They are also easy to remove when you have the right tool, so replacement after 5 years or so wouldn't be a massive chore, as long as you can get at them.

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Yesterday I did something I've not done before, I set my Jig-saw (sabre saw, in the USA) to a 45° angle. I used it to cut the egde of a board that will be on the top of an embankment and thus I wanted the start of the slope.

It has got me thinking about whether shaping the edge of baseboards with a 45° angle would be a good idea. Wrapping roofing felt round a 90° edge can be a bit difficult and a more gentle angle could make things smoother.

I guess there would be two ways of doing it, a full cut or a bevel.

   ____

/

/_____

Or

___

/

|____

Not sure that helps, but I haven't got time to knock up a drawing.

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I had the chance to felt up a relatively small baseboard today, it was 1200mm by 400mm and it will not be joined to other boards. This has given me chance to try out a few things in this thread. Here are my thoughts.

The three things I've tried are wrapping the felt over the edge, stapling the felt in place and trying a beveled edge to see if that produced a better result. Before I got to the felt I had to trim the edge to 45º. I set my jigsaw up and got an OK result.

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I attached the felt with adhesive, rolled it smooth, put bricks on the ends to stop the felt lifting and then got to work with the staple gun.

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The results with the staple gun were impressive. It was easy to keep a tight edge and staple. I kept the staples vertical which will make them much easier to remove if I ever need to do so. This did have two issues: the first was alignment, I had 10mm staples going into a 18mm edge (which was covered up so I couldn't see it). The second was that I had to use double the staples than if I had put them in horizontally.

The felt went round the 90º edge without any problems and produced a good finish without creating a raised lip on the top surface, something I was keen to avoid as it would stop water running off. With this working so well, the beveled edge wasn't required.

The 45º angle just added complication where it wasn't needed. I had to put staples in on both the 45º and 90º bits to keep things smooth and it didn't look very neat. Fortunately I did this test on an edge which will be completely hidden.

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I was in Homebase the other day and they had shed roof felt for £10.99. Has anyone used this and is it any good?

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They usually have a year rating on them. I've erred on the side of caution and gone for the stuff rated at 10 years. It's cost me £30 for 8m by 1m from B&Q.

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I laid some felt yesterday while running low on adhesive. The result is OK, but not as flat and smooth as I like. It's certainly better with a god coating of adhesive under the felt.

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I have no intentions of teaching Grannie to suck her eggs, but can't help noticing the problems that some are having using roofing felt. It is being used as a waterproofing for the base timberwork mainly, but as it has the mineral addition it is hopefully providing a ballasted look. I notice from most photographs that the wraparound is giving a wrinkled appearance, and I have seen comments about under track lumpiness. It needs to be remembered that this stuff was never intended to bend around sharp corners. Chris has the right idea with his bevels. It can be improved by warming with a blowtorch or hot air gun which will soften it. Preferably, wait for a nice warm day, and unroll the felt to warm in the sun for half an hour or so.

I have seen no mention of Sarking felt. This is a roofing felt that is much thinner and pliable that is applied to a roof before the slates or tiles are fitted. It will wrap around a sharp corner easier, and not "move" as much in temperature extremes as the mineral stuff. It will give waterproofing to the timber, but not the ballasted appearance. Perhaps a ballasting strip of mineral strip at track width on top of sarking felt would be an improvement in appearance, both to baseboard edges and realism of ballasting. Just a thought.

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I had a resistance to roofing felt at first. I just felt (had to throw that in didn't I ?) that it didn't look smooth enough on edges due to the curl issue. Since using it, I've realize it is perfect for stopping moisture damage and am a complete convert to it.

I am not sure about staples on the side like that. Seems like it's a good spot for moisture to works it's way into your baseboard and start a good rot. Are you using bitumen under the felt?

When my roof got done, a crew came out to fix some minor issues caused when part of it was installed on colder days. They used a torch to heat and bend the felt. it seems the best time to work with felt is on a really hot day.

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Roofing felt is not readily available here. I've only found on company that makes it and it's used by railway preservation societies to recover carriage roofs. Outbuildings here are almost exclusively made of "colourbond" prepainted steel. Sides as well as roofs. My garden shed is all colourbond as are my boundary fences and the roof on my house and garage.

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