MortarThePoint

Should have but didn't. It's going in on Thursday and I've a busy day tomorrow. This article suggests drilling and fixing once the mortar has set: https://www.practicalarchitecture.com/blog/how-to-detail-a-wallplate

I was wondering if there is an alternative to lap jointing the wall plate, perhaps using some appropriate hardware. I'm concerned that I won't be able to keep up with the brickies as they install the wall plate. Can something like a gang nail be used? I'd really want something that covers this application in its BBA certificate, so it is considered a good job. NHBC say "joined using half-lapped joints, including at corners", but I am sure I read somewhere that propriety fixings could be used. I feel like a bodger asking the question, but feels like there should be something just as good as a lap joint and I don't mind spending up to £5 per joint as that's what a day of a chippie would probably work out as. I'd rather spend £1 - £2 though ?

I think NHBC specify wall plate section lengths should be over 3m, but I can see a downside in going too long. The likelihood of having straight timbers will go down with increased length. Any advice as to what length is best? " - a minimum of 3m or extend over at least three joists, rafters or trusses - joined using half-lapped joints, including at corners" https://nhbc-standards.co.uk/7-roofs/7-2-pitched-roofs/7-2-6-wall-plates/

Architect specified Tyvek Supro but I don't know if for good reason. I'm inclined to go with a premium one due to the time of year etc

I am tossing up between Permo Forte and Tyvek Supro. It's going to be installed in a couple of weeks time (hopefully) so the conditions could be challenging. A Christmas shutdown probably means the membrane is exposed to the elements for longer than I'd like as well. I lean towards the Permo Forte. Any thoughts?

The thermal bridging can be reduced at shorter lengths, but as they get longer there's no choice with cavity lintels

For long spans the loading can rise considerably. Not only does the load rise in proportion to length, the resulting peak moment on the resisting member rises with the square of length: The section of the member needs to get increasingly large to resist the increased moment and still the designers typically allow a deflection in proportion to length. As I understand it, this is typically L/325. That means that a lintel for a 3300mm opening will allow a 10mm deflection at the limit. Cavity lintels for large spans (e.g. >2400mm) start to become very expensive if there are roof or floor loads near by. For example, a 3750mm lintel with a total UDL capacity of 50kN runs to around £200-£400. Steel beams have huge moment resisting capability depending on their section. There is a range of Universal Beams (aka RSJ) which have a width of 102mm well suited to a 100mm internal leaf. A 3800mm 305x102x25kg beam costs around £200. I want to understand when to swap to such a steel. Considering just universal beams for a 3400mm opening with 50kN UDL: Section Iy(cm4) Deflection Saving 178x102x19kg 1356 L/364 (9.3mm) 22% 203x102x23kg 2105 L/564 (6.0mm) 6% 305x102x25kg 4455 L/1200 (2.8mm) 0% NOTE: 254x102 UB omitted A cavity lintel would probably have a deflection of 10.5mm (L/325). Steel beam advantages: reduced deflection, greater capacity, lower cost Steel beam disadvantage: rarely galvanised and so needs careful painting etc when exposed to cavity, needs boxing in for fire protection Cavity Lintel advantages: galvanised, makes provision for outer leaf, stated capacity so no need for Structural Engineer's input Ease of installation can go both ways. At length, both are heavy. What experience do people have and when do they typically change from cavity lintels to steel beams?

We're not having any frosted windows as the nearest neighbour is about 100m away through trees, so if they ant to go to the effort of seeing me get out of the bath then their welcome.

It's inefficient, but I think I'll just wait for the dust to settle after completion.

Are those rafters at 600mm c/c

It's a new build and roof related PD rights are intact thankfully

Annoying as that will be inefficient, but shouldn't add too much cost. Do you have experience or have you seen this written somewhere in 'the rules'?

What's the situation with permitted development during the initial build? Permitted Development would allow us to add roof lights to our attic space. Do we have to wait for the build to be signed off before then doing that or can we just roll it in to the main works?

Structural Engineer specified 100x50 wallplate, I was just commenting on the article. 140mm screws sound good. Do you use the same pan head screw type you suggested above, or do you use plugs?

I saw this article which seems good: https://www.practicalarchitecture.com/blog/how-to-detail-a-wallplate They suggest "Wall plate shall be fixed to wall with Fischer SXRL10mm dia frame fixings 140mm long at max 1m ctrs in centre of wall plate, installed after mortar has set." Could be another place for a masonry screw since he Structural Engineer didn't specify the use of vertical screws through wall plate into masonry, but they seem a good idea. Not sure 75x100 is called for. I had intended to use C24 timber rather than C16

How do you seal around that without a frame and flashing?

1.2m is less than 2m so meets the requirement (maximum of 2m centres). Yes it is more straps though

Thanks Peter. They are Plasmor 7.3N Fibolite blocks

A friend has used 7.5x50 ScrewFix EasyDrive concrete screws to fix his straps to the walls and I'd like to go that way as well: NHBC say: Fixings for straps should be: in accordance with the design, and the lowest fixing should be within 150mm of the bottom of the vertical strap of a material or finish which is compatible with the straps where into masonry, hardened 4mm x 75mm nails or 50mm long No 12 wood screws (into suitable plugs). What have others done? I'm inclined to think the concrete screw will be better than a woodscrew in a plug

Interesting, thanks. Is toughened glass necessary for a roof light given its largely out of harms way?

Has anyone used these: https://www.lbroofwindows.co.uk/roof-windows/centre-pivot-roof-windows/aurora-centre-pivot-roof-window-pine-finish/

We have a loggia/veranda along part of the rear elevation and there is a window in the wall below it (pictured below). We would like to have a roof light in the loggia roof, but there is no point in it being opennable or double glazed. Can anyone recommend windows that would work well here? Separately, we want to add some non-opening roof lights to the attic space. We would want these to be double glazed, but without the opening mechanism I'd hope we could have a greater glazed area as well as save some money.

Maybe I've misremembered the number

No internal PIR, 300mm walls with U value of something like 0.26. I did a cost benefit analysis based on 100mm fibre batts vs 125mm or 150mm fibre batts and for me it didn't make sense. I then changed to blown beads very late in the game, otherwise I would have upped the cavity size since the wider cavity economics with blown beads are more compelling. With blown beads there is a fixed cost of labour and a variable cost of beads and so having a 50% larger cavity probably only adds 30% to the cost (guestimate).

100mm of EPS beads so similar arrangement just narrower cavity. You could use a concrete lintel for the inner leaf and a single leaf lintel for the outerleaf brickwork. Is there a reason you prefer the concrete lintels? They do look a lot cheaper (Condell seem very cheap). There must be a reason Structural Engineers go for the cavity lintels though.