Wall assembly advice?
astroskidder
| Posted in General Questions on
Curious what people think of the following wall assembly:
– 1/2 drywall w/ vapour barrier primer (also ADA).
– 2×6 wood frame wall w/ roxul or dense-pack cellulose.
– SONOclimat R6 structural fiberboard w/ Neopor EPS.
– Delta-Dry rainscreen.
– Horizontal 1×3 strapping @ 24″ O.C.
– Combination of vertical wood lap siding and pre-finished metal siding.
Zone 6 build in interior British Columbia, Canada… area is a designated a temperate inland rainforest.
Thanks in advance!
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Replies
Daryl,
That assembly should work. The only wrinkle I can think of is that Delta-Dry has not been approved for use as a water-resistive barrier (WRB). So if your local building code requires a WRB, you will probably want to install housewrap between your sheathing and the Delta-Dry.
For more information on Delta-Dry, see All About Water-Resistive Barriers.
Thanks Martin,
Have a look at this: http://www.deltams.ca/pdf/DELTA_-DRY_-_Technical_Paper_-_Dale_D_Kerr.pdf
I was under the impression that the Delta Dry was a WRB? I'm not a fan of house wrap, so if I need to, I'd go to building felt/paper as the WRB and use either the Delta Dry or 10mm Home Slicker.
Daryl,
The last time I spoke with representatives from the manufacturer -- admittedly over a year ago -- Delta-Dry had not gone through the International Code Council Evaluation Service (ICC-ES) process to determine whether it was an acceptable substitute for asphalt felt on walls. While ICC-ES approval is generally required in the U.S., I'm not sure what the legal requirements are for WRBs in Canada.
An update from Delta-Dry on the link I attached earlier in this thread:
"The research paper you have is old. DELTA-DRY is approved for stand alone use (that is, without a water-resistive barrier or as a water-resistive barrier) in Ontario only. That being said, we don't promote that application any longer. We promote DELTA-DRY as a rainscreen material only. DELTA-DRY requires the use of a water-resistive barrier (WRB) behind it. Since that article was published, the material is now only available in a 10 mm thickness and a profile that is different from the one pictured (which was 8 mm). If you are interested, here is a quick link to the Professional Articles page of our website wherein you can find several academic research papers on the performance of DELTA-DRY: http://www.cosella-dorken.com/bvf-ca-en/news_events/articles.php
So building paper it is then. As well, the Delta-Dry product has a listed life span of >20 years... not sure if this means 25 years or 125 years. Whatever I'm using for a rainscreen, I expect it to last a very long time... definitely more than 20 years. Rainscreen is now a toss up between the Delta-Dry and 10mm Homeslicker products... does anyone with first hand experience with both care to comment?
Rainscreen plus strapping? I would think strapping is enough. And there are many who feel there is no vertical component needed for moisture removal that is the airspace alone does the job. The other benefit is not having a fire cavity top to bottom acting like a chimney blowing air to make any flame burn like a blow torch. Also I am not a fan of vertical siding for keeping water exterior to the siding. Form Follows Function is my preference but can understand there are differences amongst us all.
"It is the pervading law of all things organic and inorganic, of all things physical and metaphysical, of all things human and all things superhuman, of all true manifestations of the head, of the heart, of the soul, that the life is recognizable in its expression, that form ever follows function. This is the law."
Daryl, Why not use the 10mm wood rain screen strips commonly available in BC lumberyards as your vertical first layer, then go with the 1x horizontal material to nail your siding to?
I don't know what type of metal siding you are considering, but corrugated profiles meet the code requirement of having only 8% in contact with the sheathing and don't require additional rain screening as long as they are installed vertically - and only a single layer of 10mm strips if applied horizontally.
I guess being in the interior you aren't subject to the code's rain screen provisions anyway, but the requirement for the first layer to be vertical, rather than horizontal (as AJ had suggested is sufficient) is a good one as it allows for both venting of the wall and a drainage plain for any bulk water that gets behind the siding.
It's either rainscreen+strapping or vertical strips+horizontal furring if going with vertical siding (board & batten) or metal sheeting. Metal siding, even if corrugated, would still need furring if using a fiberboard sheathing... even with plywood/OSB I would not be too keen on turning my wall into swiss cheese by screwing vertical metal siding directly to the sheathing.
It's a tricky one to figure out. There is a lot of labour cost in applying vertical and horizontal strapping to a wall, but maybe it would be about the same or less than applying a Delta-Dry-like rainscreen and then horizontal strapping?
AJ... can you elaborate on your comment about "no vertical component needed"... not too sure if I'm following you on that part?
Daryl, your codes and moisture... my post must be wrong for your area. Still, I am not a fan of vertical or angled sidings. Done well I am sure any look will work. Sounds like you have good specs.
Daryl, rain screen requirements have just about done away with vertically applied siding of all sorts here on the coast. I'm sorry I can't help with the relative labour costs of using a proprietary brand rain screen, having only used or specced the commonly available wood strips.
I agree that attaching siding of any type directly to fibreboard sheathing isn't a good idea but have no reservations attaching corrugated metal siding to plywood. It is very common to see it detailed that way and there haven't been any problems I have seen reported.
This month's Canadian Architect Magazine features a project on its cover with that installation technique - although in a different (Ottawa) climate.
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