Green Building Forum - timber frame roof noggin advice Tue, 19 Dec 2023 08:40:07 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299412#Comment_299412 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299412#Comment_299412 Wed, 28 Dec 2022 09:47:39 +0000 thebeacon
I have drawn up the framework for my 4x3.5m warm roof garden room. I plan to leave the roof joists unclad internally, partly to save on material and partly to give the illusion of slightly more head height.

1. How many sets of noggins would you recommend for the roof, and should they be placed central to the walls or central to the overall roof joist length?

The span will be 3.5m, although the roof overhangs at the front and back, making the roof joist length 4.3m. I am using 47 x 175mm C24 Pressure Treated Timbers for the joists.

2. Would you recommend making the noggins smaller in depth, for example, using 47x150mm and having a gap between the top of the noggin and the roof deck to allow airflow?

3. Where the roof joists attach to the top plate of the walls, would you suggest using truss clips (https://www.screwfix.com/p/sabrefix-truss-clips-galvanised-95mm-x-50mm-20-pack/72002) or angle brackets (https://www.screwfix.com/p/sabrefix-heavy-duty-angle-brackets-galvanised-90-x-63mm-25-pack/69361) on each side of a roof joist

i have uploaded an image to show the design so far.

Thanks in advance,]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299416#Comment_299416 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299416#Comment_299416 Wed, 28 Dec 2022 12:16:27 +0000 tony timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299427#Comment_299427 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299427#Comment_299427 Thu, 29 Dec 2022 11:48:08 +0000 cjard timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299437#Comment_299437 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299437#Comment_299437 Thu, 29 Dec 2022 21:50:46 +0000 Coverley
Also check the roof is tied roof down! The roof will have uplift in a gale so you need continuous load path into the walls. Either straps from the rafters to studs, or make sure there are robust connections from rafter to wall plate to studs.

ps - I'm not sure if 'blocks" or 'blocking' is the right phrase? In my mind it's when a piece of timber the same size as the rafter/joist used to close the ends rather like a noggin. It stops the rafters falling over during construction and prevents a weaker mode of failure on the minor axis. See "lateral stability" at the bottom of this link https://www.roymech.co.uk/Useful_Tables/Timber/Timber_Strength_Calcs.html]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299438#Comment_299438 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299438#Comment_299438 Fri, 30 Dec 2022 10:21:32 +0000 revor Posted By: cjardNot sure I'd bother if you're putting staggered boards on the roof deck

I agree the boards will give you the rigidity you require. However it may be prudent to fix central noggins if your joists are not straight accurately cut noggins will help to pull up the joists so that timbers are all central and so are where you expect them to be when you fix the cover boards. Alternatively you could use herringbone struts if you are concerned about air flow.]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299439#Comment_299439 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299439#Comment_299439 Fri, 30 Dec 2022 11:08:29 +0000 thebeacon
Is it ok not to place the blocking over the top plate? Ideally, I would like to insulate that space with 90mm pir board.

I was thinking of putting the blocking just off the top plate, use these angle brackets to attach the rafters to the top plate (https://www.screwfix.com/p/sabrefix-heavy-duty-angle-brackets-galvanised-90-x-63mm-25-pack/69361) and then insulate in the gap between the rafters and top plate.

I have mocked up an example, highlighted in blue, in the image.]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299440#Comment_299440 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299440#Comment_299440 Fri, 30 Dec 2022 17:47:17 +0000 cjard
https://www.screwfix.com/p/turbocoach-hex-flange-coach-screws-m6-x-90mm-500-pack/2793x]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299445#Comment_299445 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299445#Comment_299445 Sat, 31 Dec 2022 12:32:12 +0000 Coverley
Metal truss clips in the same plane as the insulation will be a lovely cold bridge and condensation magnet. As tony and cjard say, use screws to connect wood to wood.

Screws will be more than strong enough bearing mind most traditional rafter roofs are held together with ring shank nails. Unless your precise with your hammr you'll find screws easier to position the timbers without them getting knocked out of alignment as you hammer in nails.

I use Screwfix turbogold because they are lethally sharp and will glide through the timber with an impact driver. They only have a smooth shank for 100mm and above but you'll need that sort of length anyway for skew nailing the rafters to the studs.

I still think you need a wedge or birdsmouth under the rafters on the wall plate]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299446#Comment_299446 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299446#Comment_299446 Sat, 31 Dec 2022 13:27:29 +0000 thebeacon Posted By: CoverleyMetal truss clips in the same plane as the insulation will be a lovely cold bridge and condensation magnet. Thanks, this is good to know.

The walls won't be insulated before i put the roof joists on, but I will have put the osb3 sheathing on the outside. I won't be able to screw the roof joists in from under the top plate because they will be sat directly over the stud joists. That's why I was thinking of using the angle brackets. Would truss clips (https://www.screwfix.com/p/sabrefix-truss-clips-galvanised-95mm-x-50mm-20-pack/72002) result in the same problem? Would using a thermal break tape help?

Posted By: CoverleyI still think you need a wedge or birdsmouth under the rafters on the wall plate
Yes, I have now drawn cutting in very shallow birdsmouths under the rafters so they sit flush on the top plate.]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299448#Comment_299448 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299448#Comment_299448 Sat, 31 Dec 2022 21:40:57 +0000 Coverley
If you have 45 wide rafters then I'd get a 120mm turbogold screw. Hypotenuse of a 45mm isosceles triangle is angle is 56mm so 120mm should give you roughly 50mm embedding in the wall plate below.

Hold the screw perp to the rafter side at roughly 40mm up, give it a few turns with an impact driver until it bites maybe 3 to 5mm into the timber, then move the screw to 45 degrees and drill through. That initial bite avoids the screw skidding along the surface if you try to go in at 45 from the start.]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299449#Comment_299449 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299449#Comment_299449 Sat, 31 Dec 2022 22:11:52 +0000 tony timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299460#Comment_299460 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299460#Comment_299460 Mon, 02 Jan 2023 10:51:28 +0000 thebeacon Posted By: CoverleyJust skew screw, like skew nails but with screws. You want to visualise a screw going in at 45 degrees on each side of the rafter.


Thank you for this advice. Will screw the rafters to the top plate using this technique]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299787#Comment_299787 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299787#Comment_299787 Fri, 20 Jan 2023 21:19:24 +0000 djh timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299809#Comment_299809 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299809#Comment_299809 Sun, 22 Jan 2023 18:08:36 +0000 cjard
Can't see where anyone said it was going to be a balcony too?]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299814#Comment_299814 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299814#Comment_299814 Sun, 22 Jan 2023 20:07:12 +0000 djh Posted By: cjard> need to be able to support a person standing on that edge

Can't see where anyone said it was going to be a balcony too?It's not a balcony. It's in case somebody accesses the roof for some maintenance purpose, AIUI.]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299835#Comment_299835 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=299835#Comment_299835 Tue, 24 Jan 2023 07:27:21 +0000 cjard timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=300021#Comment_300021 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=300021#Comment_300021 Tue, 31 Jan 2023 16:48:47 +0000 thebeacon
I have been looking more closely at roof insulation and waterproofing and came across Kingspan QuadCore Insulated Composite Panels KS1000RW (https://www.steelroofsheets.co.uk/products/kingspan-ks1000rw-quadcore-insulated-composite-panels/). They are Kingspan insulation with a painted metal sheet. They are structural. It could make installing the insulation and waterproofing the roof a quicker and simper job.

Although they are aimed at industrial use, they have been installed on other garden rooms: https://www.youtube.com/watch?v=VXns2_C2ScI&list=PLjE4kW4I9DKUxeXWQPinMmyrV4EPlo1TL&index=7

I am considering two options in which they could be installed:

Option 1:
140mm Kingspan panel
Wall top plate

Sit the Kingspan QuadCore Insulated Composite Panels directly onto the top plate of the walls and fix it in. From looking at their span table, I wouldn’t need joists. This would mean the underside of the panel would be the internal ceiling.

Option 2:

140mm Kingspan panel (or slightly less)
Vapour barrier
11mm osb
100mm joist
Wall top plate

With option 2 I would still put joists over the roof but 100mm now rather than 150mm, with 11mm osb covering it. This would be because I would prefer a wooden ceiling compared to the underside of the Kingspan QuadCore. The roof joists would only need to take the load of the osb as the quadcore panels would take their own weight.

Does anyone have experience with these types of insulated panels? Or can see glaring oversights in my thinking?

Thanks,]]> timber frame roof noggin advice http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=300025#Comment_300025 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17682&Focus=300025#Comment_300025 Tue, 31 Jan 2023 17:56:14 +0000 djh Posted By: thebeaconWith option 2 I would still put joists over the roof but 100mm now rather than 150mm, with 11mm osb covering it. This would be because I would prefer a wooden ceiling compared to the underside of the Kingspan QuadCore. The roof joists would only need to take the load of the osb as the quadcore panels would take their own weight.Sounds like a lot of effort to get a surface finish. Presumably you could just paint the underside of the roof panel? Or maybe glue whatever surface veneer or suchlike to it?]]>