Leaky playhouse

[Tryhard61]

Hello, has anyone any idea what could be the problem here please.
We have put together a 7x5 playhouse , bought from a reputable company. All went well We clear Cuprinoled a week before it was built and left it to dry ( in the garage) and covered it with Cuprinol shades , 2 coats, as soon as it was up . It leaked right across the bottom half of all the laps (t&G cladding) . We filled every nailhole in all the panels, masticked around the windows, and up and down every corner joint , the butted together uprights, AND where they had attached the cladding to the frame. It leaked on the prevailing weather side. We put a third coat of Shades on , and checked over the mastic. No gaps - yet it still leaks across every lap ( about an inch above and below) for the first 2.5ft from the ground,as if they are just butted together and the water seeping in. (They arent of course, all the tongues are slotted in properly) We have bought gutters, not yet on, but I cant see them making any difference. Any ideas what is going on please? (Its a concrete base, and then sits on extra 1x1 wood underneath its own frame .)

 

[fencer35]

Although you say there is extra 1 x 1 under floor joists have you checked for splash back from the concrete?
Also are ther vertical corner beads & are they siliconed in ?
What did you use to seal the nail heads?

 

[Tryhard61]

Hi there, yes there will be some splashback from the concrete, till the gutters go up, but I still cant see how the water can get in . Three coats of Shades has appeared to have thoroughly sealed where each overlap is even if it splashes upwards --and 2.5ft seems pretty high for just splashback? (They dont say it requires gutters) , and yes all corners are really well siliconed in (although no vertical beading ) I used ready mixed tube of woodfiller suitable for int and ext - cant remember the exact name now. Im thinking perhaps Im going to have to mastic along every lap joint. OK till you want to renew the preservative which then wont stick. http://www.waltons.co.uk/waltons-snowdrop-cottage-with-loft-7x5 you can see the construction here.
The company offered me a new side panel, but that would mean taking the roof off, dismantling and rebuilding (and the person who put together the first one for us is no long available) and then spending out another load of money on more preservative , more Shades and more filler and mastic. Theres no guarantee the new panel wouldnt leak either seeing as we cant see whats wrong with the old one.

 

[fencer35]

Looking at it, I wouls still try and get some kind of corner strip on there even an 'L' shape to protect the corners I'm not saying this is the problem but I seen alot of sheds wet because of this.

 

[Tryhard61]

Yeah, thanks, Ill probably do that as well as the gutters . Cant believe it getting so wet though. Even wondered if maybe the Cuprinol Shades stuff was faulty and is not actually waterproof ! Thats not very likely, so I suppose if I end up having to mastic every lap, it WILL be dry !

 

[fencer35]

cuprinol shades is pretty good stuff tbh.
Another idea !.....take them up on the offer of a new side and simply srew it over the top of the other. double the protection ?