Shiplap (cont) problem...

[ellal]

Having had our first decent rainfall for ages, I've noticed that there are areas where water has ingressed the new shiplap that I've put on a workshop build..

To recap how it was put up:

Vac treated 'redwood' shiplap was left for 5 days before using it.
So far 4 coats of tung oil have been applied as recommended here.
corners were silicon sealed and then corner pieces build over the joins.

Water is ingressing at the corners, but also in certain horizontal stretches.
I was advised by the wood suppliers not to put felt behind the shiplap, as if water did get through it would be 'trapped' and cause quicker rotting.

I have noticed from the inside that the shiplap does develop gaps of approx 1mm dependant on temperature/humidity.

I am planning to put insulation and OSB3 on the interior walls to make it easier to put up shelves/storage wherever I want, but obviously need to find out what I may have done wrong before I can proceed further.

I have put up some photos Here to give an idea of some of the areas where water is getting in. (shed20 - shed23)

Any ideas gratefully appreciated, as I want to be able to get on with the interior.

Cheers

 

[big-all]

mmmmm 5 days

should have been several week to dry out properly

i gave mine 3 weeks in doors[house] fully seperated in a warmish well ventilated room till it looked and felt right
also 2mm bigger than the dry sample i asked for so during the hot weather it would shrink and when wet it would have room to expand


wwwwrong

during the summer it shrank so much i had to remove all the cladding tighten up again to within 2mm again for expansion
approching 2" shrinkage over 6ft high

i had simmilar problems with the toungs comming out the grooves

 

[gord55]

Having fixed a LOT of shiplap over the years, I would never consider putting it up without a moisture barrier like felt... unless you really don't mind the inside getting wet.

Thin timber in this changeable country will always move and allow gaps, so personally I wouldn't even allow one day for it to stabilise (unless it was very wet when bought) - I'd put it straight on, with felt behind it & hope for the best. It's going outside, after all, & if it's been lying on a covered rack outside then it's going to be somewhere near the right moisture content anyway. I don't see the point in trying to dry it further.

I have three "sheds" locally I've built, the oldest being 18 years, and none of them leak or show signs of serious decay. It really is a waste of time in this country to expect timber to stay where you put it.
Also, silicone will work for a while.
At corners, I would leave a 90° space (in other words, the boards on adjacent sides just touch each other at the corners) & run a big bead of silicone down, & then fix a corner cover piece (L-shaped in section) over the top. (Sorry ellal, I've just re-read your post... that's what you've done!)

The climate here is unsuitable for external joinery.

 

[big-all]

heeelllooo gord 55

unless i am misunderstanding this the wood was 5 days after vacuum treating e g saturated and not air dried

and a controled level of drying is reqired to stop the shiplap opening up
the wetter you attach it the more it shrinks!!!!

 

[gord55]

...and I should have said what an excellent job you've done of it, after seeing your pics.
No need to despair however (should you decide to use felt after all) - put it behind the insulation, and fit a few vents around the bottom of the inside wall. Or even one vent in each section (i.e. between each pair of uprights). Circular soffit vents should be fine.
There are other ways, but that's probably the simplest.

 

[ellal]

Thanks for the replies..

I thought about the felt option, but was put off it by the advice of the wood suppliers..If it wouldn't affect the wood, I would consider removing the shiplap, and fitting felt - I like to do a proper job, so all that's needed is a dry weekend! But wouldn't that mean that water would still get in and the shiplap rot, even given it has been vac treated ?

However, the suggestion of putting the felt behind the insulation is interesting. I assume you mean cutting out for each panel, but do you suggest fixing it to the shiplap from the inside? And am I right in thinking that a vent at the bottom wouldn't have any effect on sections above as I have put in 2 horizontal cross pieces (oops - just seen you put that in your post gord) , . Also, the water would still ingress, and I assume eventually attack the shiplap & the framework (even though the timber has had several coats of preserver)..

cheers

 

[gord55]

And helloooo to you big-all. Yes, you're right - I didn't twig about the vac treatment. I'd leave it much longer to dry (& shrink) a bit, if only to give the oil a chance of getting in. What do you think about a moisture barrier?

 

[gord55]

Yes... sorry ellal, our posts are crossing here. I don't mean cut the insulation between, just put felt behind it when you fix it to the timber as normal. The 2" gap will allow circulation of air (albeit usually DAMP air) and yes, you'll need vents at the top too.
I know from experience that water WILL get in, and will eventually affect the shiplap and the framing. As your boards are vac-treated, they'll last considerably longer than untreated stuff, and the best advice I can give is to do the best you can & then forget about it. Enjoy your well-made (& waterproofed) shed...

 

[masona]

Run a clear sealant on the edge of the L-shape and inside the gaps, it maybe blowing or rain in an certain angle or the shiplap is not quite level so rain running into the corner.

Or you may have a slight hairline spilt that you cannot see, if so, treat over it with more with tung oil.

Never has any problem with my summerhouse this way.

Great job you're doing there.

 

[ellal]

Sorry gord, just to clarify..did you mean normal installation of felt - i.e from the outside, shiplap, felt, frame, insulation, OSB board. Or as it stands, shiplap, frame, insulation, felt, OSB Board with ventilation (online descriptions always lead to confusion, especally when at my end it is my first time building this standard of workshop.)

Masona, I can put sealant in the corner joints Ok, but will the silcone work in horizontal joins, if there will always be movement? And I intend to put on at least another 2 coats of oil weather permitting..

 

[gord55]

As it stands. To take the boards off would be the very last resort & definitely not the way to go from here. A 2" air gap between shiplap & felt isn't a bad thing at all... after all (in my opinion) water will get past the shiplap anyway & at least it won't be trapped between the shiplap & the felt.
Re silicone: masona is right, it's worth squeezing it in where you can. Even if the joint breaks with the movement of the boards, the silicone will create a smaller gap for water to get through. And I shouldn't worry about water & small gaps (=capillary action) because that's what you're going to get anyway.

 

[ellal]

Ok, so my best move from here would be to silicone the gaps (inside or outside, which is best?).

The main frame is 3x2, so if I put the felt on from the inside, how do I make a 2" gap for the insulation?

cheers

 

[gord55]

Silicone probably from the outside, but less unsightly from the inside - and also wouldn't spoil the exterior surface for the extra oil coats.
Sorry, assumed 2"x2" (3x2 much better!). You'll have a 3" air gap.

 

[ellal]

Silicone application should help then..

But I'm still puzzled about where the insulation would actually go. I was planning to put in 'sheet rockwool'. but are you saying that the gap between the shiplap and OSB should be OK insulation-wise (without the rockwool), and therefore give an adequate airgap?.

 

[big-all]

And helloooo to you big-all. Yes, you're right - I didn't twig about the vac treatment. I'd leave it much longer to dry (& shrink) a bit, if only to give the oil a chance of getting in. What do you think about a moisture barrier?

i am as undecided as yourself about felting gord 55
several people have suggested builders membrane as i believe it can breathe
by this stage in the procedings i had expected to insulate and board with 12mm mdf or ply but the conflicting suggestions about moisture retention and rotting so still undecided