epsilonGreedy Posted July 20, 2021 Share Posted July 20, 2021 (edited) I have found a slater who can spare a few hours each week to guide me through slating a trial small roof 4.3m x 3.1m. Lead work is also one of his specialities so we have decided on a roll top ridge and two toll top hips. My challenge is to now fit a ridge board on which I can mount a wood roll ridge that will provide the former for lead roll ridge. The ridge board will have to slot between existing trusses at 600 centres. As an extra coplexity multiple slaters have voice their strong objection to fitting natural slate on 2" x 1" battens across 600mm centres, therefore I have agreed with my man to retrofit extra rafters to reduce the centres to 300mm. So the motivation for this post is to solicit any creative bright ideas on a carpentry solution for the ridgeboard retrofit and the supplementary rafters. Given the small plan size of the roof and the single hip end the ridge is only 2.5m long. I think I will be using 2" wood roll (my man calls it "mop stick") although a 3" version is available. Therefore I assume this will require a 40 to 45mm thick ridge board to provide a nice mount. I will square off the peaks of the trusses sufficient to match the width of the ridge board. I anticipate cutting deep sections out of the ridge board so that it can be dropped down and slot between the trusses with about a 60mm continuous section running over the top of the trusses. It is a 30 degree pitch roof. I hope lateral stability will come from the extra rafters fitted midway between the trusses. The slater and I talked about the engineering of this and concluded the forces on the ridge board will be low, just a little aerodynamic lift during a stormforce gust and all nicely weighed down by code 5 lead. Edited July 20, 2021 by epsilonGreedy Link to comment Share on other sites More sharing options...
Oz07 Posted July 20, 2021 Share Posted July 20, 2021 You in effect just need to nog between the trusses to give you a nice flat surface to sit the roll on? Most roofers with dry ridge screw a batten along the top of the trusses at the peak to fix down into. Couldn't you do this Then fit roll ontop of that. 2x1 batten is fine for 600 slate is lighter than concrete or clay. Link to comment Share on other sites More sharing options...
Oz07 Posted July 20, 2021 Share Posted July 20, 2021 It's not got to be 1 continuous piece get that out of your head straight away. You be also not got to square the tops off just lift the nogs up so they finish at peak level or higher. You're over thinking this. 1 Link to comment Share on other sites More sharing options...
Temp Posted July 20, 2021 Share Posted July 20, 2021 1 hour ago, epsilonGreedy said: As an extra coplexity multiple slaters have voice their strong objection to fitting natural slate on 2" x 1" battens across 600mm centres, Presumably because its hard to hammer nails into springy battens? Would 2*2 battens solve the problem? Link to comment Share on other sites More sharing options...
Temp Posted July 20, 2021 Share Posted July 20, 2021 3 minutes ago, Temp said: Presumably because its hard to hammer nails into springy battens? Would 2*2 battens solve the problem? Just read the OP again... 1 hour ago, epsilonGreedy said: the ridge is only 2.5m long. So just 4 bays or 8 rafters. Should be simple enough. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 16 hours ago, Oz07 said: You in effect just need to nog between the trusses to give you a nice flat surface to sit the roll on? That was the original requirement but since the roofer has described the negatives of nailing slates on 600 centres I now intend to butt extra new intermediate rafters up against the retrofitted ridge board. I assumed that a continuous ridge board with sections cut out to accommodate the existing trusses would be a stronger and less fiddly solution than separate noggins. 16 hours ago, Oz07 said: Most roofers with dry ridge screw a batten along the top of the trusses at the peak to fix down into. Couldn't you do this Then fit roll ontop of that. Do they knock off the peaks of the trusses before fitting the batten? Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 16 hours ago, Oz07 said: You're over thinking this. The story of my selfbuild. 16 hours ago, Oz07 said: It's not got to be 1 continuous piece get that out of your head straight away. You be also not got to square the tops off just lift the nogs up so they finish at peak level or higher. If the ridgeboard is not continuous I will have to fix each nog butt end to the truss side somehow, would I use metal fixing for this or rough cross nailing or some smaller battens to form a slot on the side of a truss that the nog can slide down and slot into? Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 16 hours ago, Temp said: Presumably because its hard to hammer nails into springy battens? Would 2*2 battens solve the problem? Yes this is problem, the roofer went to great lengths to explain the extra force required to hammer down nails against the inherent spring across 600 centres. He said that sometimes the damage from over hammering is not immediately visible but slates will crack over the next few years. His boss who is very helpful on the phone and offered to pass by my site to provide free advice said "even if I was not fully booked for the next 12 months with 4 re-roofs booked I would decline to quote for a natural slate job on 600 centres". I costed out fitting oversized battens e.g. 2x2 or 2x3 was told this would not result much improvement to the spring across 600. He was far more positive about adding extra rafters to create 300 centres. Link to comment Share on other sites More sharing options...
Oz07 Posted July 21, 2021 Share Posted July 21, 2021 Tosh nail same as you do a noggin between 2 pieces. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 16 hours ago, Temp said: Just read the OP again... So just 4 bays or 8 rafters. Should be simple enough. Yes 4 bays plus the equivalent extra jack rafters around the hip end. Will need 6 extra jacks to keep the max span down to 400. It it less than 2m from ridge to wall plate so within my capability range I hope. However if this works out then the same retrofit solution will be applied to the main roof. I might need more chunky wood for the extra intermediate rafters up there. Link to comment Share on other sites More sharing options...
Oz07 Posted July 21, 2021 Share Posted July 21, 2021 Insane. I've honestly seen loads of 600 centre trusses have a slated roof ontop. What's he using a toffee hammer 1 Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 (edited) 6 minutes ago, Oz07 said: Insane. I've honestly seen loads of 600 centre trusses have a slated roof ontop. What's he using a toffee hammer Such diverse practice is at odds with what I am hearing. The first time the 600 centres were discussed with a slate roofer having 30 years in the business he visibly winced when I said I had just fitted trusses at 600. He was finishing his retirement property with a slate roof and trusses at 400mm. Then last week another small family roofing business said the same about 600 centres. I am mid way between Lincolnshire's two main towns and these two businesses operate from opposing ends of the county. Edited July 21, 2021 by epsilonGreedy Link to comment Share on other sites More sharing options...
markc Posted July 21, 2021 Share Posted July 21, 2021 5 minutes ago, epsilonGreedy said: Such diverse practice is at odds with what I am hearing. The first time the 600 centres were discussed with a slate roofer having 30 years in the business he visibly winced when I said I had just fitted trusses at 600. He was finishing his retirement property with a slate roof and trusses at 400mm. Then last week another small family roofing business said the same about 600 centres. I am mid way between Lincolnshire's two main towns and these two businesses operate from opposing ends of the county. Loads of old slated roofs done without trusses, two walls, possibly a ridge board but many without, a couple of purlins and rafters at 2 ft centres. 2x1 slate lathe on top of that and get nailing. the 600 or 400 centres are to do with the trusses themselves, not the lathes. If you get the odd springy (or a knot in the middle) lath then it is supported by the slating hook or bit of timber while nails are knocked in. Link to comment Share on other sites More sharing options...
Russell griffiths Posted July 21, 2021 Share Posted July 21, 2021 Can you not sark the roof Scottish style, 100x25 all over with 3mm gaps between boards. Fitting jack rafters between trusses is just insane. You might as well take the whole roof off and move the trusses along and buy a couple of extras. 3-4 packs of 100x25 and a nail gun, be all on in a couple of days. Link to comment Share on other sites More sharing options...
Mr Punter Posted July 21, 2021 Share Posted July 21, 2021 600 centres is standard for trusses here. Have you considered using slate hooks instead of nails? No slates rattling in the wind and they seem more secure. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 13 minutes ago, Russell griffiths said: Fitting jack rafters between trusses is just insane. I think the term "jack rafter" only applies to the mini rafters that butt up to the hip rafters at 45 degrees. I fitted the original jacks at 600 centres. Not a big deal to drop in extras I feel. 16 minutes ago, Russell griffiths said: You might as well take the whole roof off and move the trusses along and buy a couple of extras. I am considering this for the main roof particularly the small L-section with a 4m clear span. The truss manufacturer dropped to a smaller truss wood cross section for these and I was not happy with their general feeblness. The hip rafters are lightly fitted at the end of this main roof section so not a big deal to order 4 extra trusses to close up the centres there. I am concerned that the original trusses were made off a master acting as a pattern, so unless the truss manufacturer takes one back to the workshop for reference the extra trusses might be a few mm out which in turn will induce a curve to the laths and so kick some slates out of a true flat lay. Link to comment Share on other sites More sharing options...
Dave Jones Posted July 21, 2021 Share Posted July 21, 2021 1 hour ago, epsilonGreedy said: Do they knock off the peaks of the trusses before fitting the batten? no, double batten normally to take the dry ridge. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 12 minutes ago, Mr Punter said: 600 centres is standard for trusses here. Have you considered using slate hooks instead of nails? No slates rattling in the wind and they seem more secure. I would if I could find a reference property with hooks nearby. I have been told recently that conservation areas are graded differently and my village is in the highest (most demanding) category. Anyhow I will start with the small single story utility room roof (4.2m x 3.2m) and use the experience here before deciding on a plan of action for the main roof. I will need to protect the lower roof from bits flying off the main roof because I am doing things the wrong way around. Link to comment Share on other sites More sharing options...
markc Posted July 21, 2021 Share Posted July 21, 2021 3 minutes ago, epsilonGreedy said: I think the term "jack rafter" only applies to the mini rafters that butt up to the hip rafters at 45 degrees. I fitted the original jacks at 600 centres. Not a big deal to drop in extras I feel. I am considering this for the main roof particularly the small L-section with a 4m clear span. The truss manufacturer dropped to a smaller truss wood cross section for these and I was not happy with their general feeblness. The hip rafters are lightly fitted at the end of this main roof section so not a big deal to order 4 extra trusses to close up the centres there. I am concerned that the original trusses were made off a master acting as a pattern, so unless the truss manufacturer takes one back to the workshop for reference the extra trusses might be a few mm out which in turn will induce a curve to the laths and so kick some slates out of a true flat lay. Unless it is a very small manufacturer who makes each truss individually, they should all be roughly the same (within 5mm) Trusses are designed by computer that also spits out the cutting list with all angles, They are assembled one at a time and then rolled or pressed, they are not assembled over a master. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 1 minute ago, Dave Jones said: no, double batten normally to take the dry ridge. Hmm the mop stick for the lead roll ridge will need a horizontal bed I feel. Link to comment Share on other sites More sharing options...
Dave Jones Posted July 21, 2021 Share Posted July 21, 2021 its not really important for the dry ridge system that the battens are dead flat, nothing stopping you knocking the top 25mm off the top of the trusses to get a dead flat bed for some batten to lay on just keepo clear of the metal webbing. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 2 minutes ago, markc said: They are assembled one at a time and then rolled or pressed, they are not assembled over a master. I was told to make sure all the trusses were oriented the same way so the "*" marks were along the same wall plate. The reason given was that all trusses are checked against the master in that orientation. They are a mid sized outfit. Link to comment Share on other sites More sharing options...
epsilonGreedy Posted July 21, 2021 Author Share Posted July 21, 2021 5 minutes ago, Dave Jones said: its not really important for the dry ridge system that the battens are dead flat, nothing stopping you knocking the top 25mm off the top of the trusses to get a dead flat bed for some batten to lay on just keepo clear of the metal webbing. Thanks. At a 30 degree pitch there should not be too much wood to knock off to get that 25mm base. Link to comment Share on other sites More sharing options...
Oz07 Posted July 21, 2021 Share Posted July 21, 2021 1 hour ago, markc said: Unless it is a very small manufacturer who makes each truss individually, they should all be roughly the same (within 5mm) Trusses are designed by computer that also spits out the cutting list with all angles, They are assembled one at a time and then rolled or pressed, they are not assembled over a The trusses I've recieved are sometimes nothing like each other. That's why it's always tag to same side then fix to a line. Diminishers are the worst. The lads knocking these up on the line are on low wage. @epsilonGreedy ask a local wood yard to do you some 50x38 treated or use 2x2 if you're worried. Anything else is mental Link to comment Share on other sites More sharing options...
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