Shiplap (cont) problem...

[gord55]

Sorry for the confusion... I've come to my senses at last. I've been doing my accounts for last year, & I need more time to recover.

Rockwool is not the best option here, you don't want to risk getting it wet.

I think I would use 2" Jablite or similar polystyrene slabs cut in between the framing, but spaced 1" off the back of the shiplap. That would bring it flush with the 3" framing, for the OSB. Felt wouldn't really be necessary then. I would still put vents in, but cut also through the poly slabs.

So now you have shiplap, 1" airgap, 2" polystyrene, OSB.

Not sure if poly is better than Rockwool for insulation, though.

Anyone else out there with better ideas??

 

[ellal]

Got it now..(I sympathise with 'accounts head' - I've got mine to do next month!..).

I'll put the silicone in the gaps, and ventilate the framing through the insulation.

I'll just have to accept that water will get through somehow, and hope that the vac treatment does it's job!

Cheers.

 

[masona]

I'll just have to accept that water will get through somehow,

Shouldn't do, I tung oil my summerhouse before summer and end of summer and never has any leak so far the last 3 yrs.

 

[ellal]

I'll just have to accept that water will get through somehow,

Shouldn't do, I tung oil my summerhouse before summer and end of summer and never has any leak so far the last 3 yrs.

So there must be a problem with the way I have put the shiplap on then, as the water seems to be repelled quite well from the surface of the wood by the tung oil.

I suspect there must be some sort of capillory action occuring, but a visual inspection shows virtually no gap on the shiplap 'overlap'..

 

[big-all]

ok several thoughts here

the gap has probably closed up as in surfaces got wet expanded and now touching
try shinning a bright light in the areas of dampness !!
the only area of trouble i have had was with dead knots leaking so i knocked them out and clear mastic in place

in your case i wouldnt expect any mastic to seal any gaps other than temporeraly because your boards are oiled and the expansion of the wood will be in the region of 4mm
fitting a gutter would help as the amount of water hitting the side must be multiplied several times as you have half a roofs worth of water aimed at the wall plus the splashback !!!!

 

[ellal]

A gutter will be going on (when I've worked out where to run the outlet without causing pooling elsewhere - a couple of waterbutts maybe...), but the other side of the shed also had water seeping in, and there's virtually no splashback due to the ground being lower and not concrete.

I suspect that the joins higher up were also protected by the roof overhangs, so I need some 'horizontal rain' to test that theory! (or maybe a hose..).

You're right about the gaps..on drying, from the inside gaps appear between the boards, and in damp weather they close, with the biggest so far being less than 2mm (and obviously the areas where water comes through tighten up the most!)....and in very bright sun conditions, some light can be seen through the joins.

I must admit though, I wasn't expecting to get any leaks, so I still suspect I have done something wrong in the construction method. (starts pondering about whether T&G should have been used instead... )

Still, despite the frustration, it's a learning experience!!

 

[big-all]

ok a couple of thoughts here!!!!
if the water comming in an its an immediate worry
you could temporary protect the outside to help it dry out a sheet of 6mm ply angled slightly to give protection and airflow would do
when its as dry as its going to get flood the area inside and out with the oil

my thinking here is some of the area isnt saturated with oil which is allowing penetration
if the wood is thoroughly coverd and penetrated with oil its less likely the water can find a path and more likely to shed the water[no pun intended ]
and hopefull the only chance of water getting in will be when the wind drives the water drops through the crack in drier wether

 

[ellal]

I put the oil on as liberally as possible, and tried to work it into the joins, but obviously the top of the 'tongue' won't have had any..

We have about 4 days of dry weather forecast, so would it be wise to try another coat of oil, say after 3 days? - would the shiplap have dried sufficiently, given that the temperature is now not that great.

Also, I'm a bit wary of applying the oil if there is a possibility of rain after a day or so, and I have noticed that a couple of areas where I put the last coat (not the areas of the leaks), have a slight sheen, and are still slightly 'oily' to the touch - as if the oil hasn't fully penetrated. Again, maybe due to the temperature.

 

[masona]

Can you give us another photo of a off-cut shiplap on end, I want to see the shape of it and how big the rebate is.

 

[big-all]

to be honest i dont know at what stage to apply the oil !!!

the stage to do it is where theres insuficiant water to keep the oil from penetrating !!!
someone else may have a better idea if the oil will penatrate and push the water out !!!! personaly i dont think it will
because of the damp evenings i would suggest covering the area and wait several days just to be safe this has the added advantage of keeping it dry if it rains but as i say leave room for air flow

my ideas are actualy educated guesses as i have never used "oil "to protect exterior wood

good luck

 

[ellal]

Thought I'd share this tip I've just been given..

My other half is from Iceland, and one of her cousins is a carpenter..normally their syle of woodwork is very different (all concrete houses etc), but then I remembered that they do have a lot of summerhouses in some very exposed parts of the country (they have rain there that defies the laws of physics!!)..

So he says that what they do is build the frame, then put felt on the outside of the frame. On top of the felt they then put thin battons, and finally fix the shiplap onto the battons. Therefore, there is an airgap between the shiplap and the felt, and any penetrating water just goes downwards and out!..

On the inside, they put insulation within the framework, then a breathable membrane, and lastly the inner wall of your choice.

It sounds quite a good way of doing it, and not a very expensive or difficult option to alter the outside..

What do you all think?

 

[gord55]

Sounds excellent ellal, but you'd have to start again...

 

[ellal]

gord - maybe an improvement for next year..

masona - I'll try and get a pic in the morning

 

[Thermo]

just a thought, as the water ingress appears to be coming from areas where you have the vertical framing and spreading out from there (pics 21 and 20) its not finding a way down through the fixings youve used in those particular areas is it? if its been mis nailed and opened up around it, it may be finding a way in through there. Shiplap by its nature of design should not allow water penetration as it has a drip at the bottom of each board, and it really has to go some to get through the joins.

 

[ellal]

Thermo - the fixings are above where the water seems to be coming in, and there are some wet areas not photographed when the rain had gone on longer, that were not on the vertical frame.