shiplap shed shrinking

[martinT198]

I purchased a tongue and grove shiplap shed last year. The shed is tanalised and I haven't put any additional overtreatment on it. In the last week since the weather has dried out the boards have shrank. There are now air gaps in several places. The edges of the boards have warped so when the humidity increases again the tongues and groves will not line up and the boards will crack.

What can the company who installed it do to remedy the situation? I have a feeling they will be 'difficult' in resolving it.

 

[big-all]

in my humble opinion wrongly put together
in the heat off the summer you should have a 2 or 3mm gap between the back faces with the tounge and groove still overlapping by around 5mm there should never be any daylight

the trouble you will have is not "treating according to manufacturers instructions"

i would go back to place of purchase and point out the problems and argue that the gaps are far far greater than they should be even iff fully and correctly treated

 

[martinT198]

Thanks for the reply. The company website says

"Tanalised timber does not need any further maintenance treatment but will naturally weather over the months finally changing to a grey colour. This is caused by the effect of sun, moisture, wind and other exterior conditions. The efficacy of the preservative continues. The timber will produce cracks (checks) that will open and close as an effect of condition changes. They are not detrimental to the long term durability of the product, but do alter the look of the furniture. "

So I think they might struggle to argue it hasn't been treated properly.

In order to make it watertight I guess the only option is to replace all the cladding. Would it be acceptable for them to line it?

Martin

 

[^woody^]

Timber shrinkage is natural and unpredictable. It will depend on several factors how cladding reacts to the various seasons, and a bout of very dry weather like last week after a damp few weeks can cause shrinkage such as this.

It does not have much, if anything to do with preservatives or coatings, as the timber will breathe in any case. If the shed was Cedar, then it will not require any treatment, but as it is tanalised, then this suggests Softwood/Redwood which is dimensionally unstable and prone to significant movement as humidity changes

The only recourse is to claim poor quality manufacture (insufficient fixings) or poor material choice/storage - but you will have a hard time proving that the shed is generally defective, and the costs and time will be way in excess of the value of the shed.

Basically if you have paid a cheaper price for a softwood shed, then you will have live with the gaps which will develop in this type of shed

 

[martinT198]

Thank you. Not what I was wanting to hear but a fair point. However, I would still expect a shed to watertight over the first year of its life. Would you not expect the timber to have been stored inside for a period to reduce the moisture content before assembly?

 

[big-all]

your problem is not the natural movement off the timber its the fact that they didnt make the nessisery allowances for the dampness off the timber
in other words if the timber is to wet when assembled you cant get it close enought to allow for shrinkage during the summer months
assuming its 5" shiplap the coverage will around 106mm fully dry as in hot dry summer
so if your is 106 you space it at 108/9mm so it has room to expand in the winter
if your timber is greater than 111 you run the risk off seperation because you cant get the boards tight enough together

may i respectfully suggest you get them to come and have a look as seperating boards are not acceptable cracks you may expect in the odd board but not to many

 

[martinT198]

Thanks for all the advice. I have contacted them today and apparently someone will be coming over sometime this week to have a look. I will believe it when I see it but at least now I have some technical expertise to throw behind my argument.

 

[^woody^]

your problem is not the natural movement off the timber its the fact that they didnt make the nessisery allowances for the dampness off the timber

I can't see how that would be possible.

The boards will have been machined with standard depth tongues and grooves. There would not be any 'allowances' as such in assembly, as the boards will have been fitted so that they piece together tightly

So either way, whether too wet, too dry or normal moisture content, it will all depend on how deep the machined tongues and grooves are.

But it is still possible for certain timber boards to be more susceptible to movement (grain, knots, tanalith salts etc) so whatever is done, certain boards will still potentially move more than others.

But I'd certainly agree that one buys a shed for security and a certain amount of weather resistance, and boards opening, cupping or warping excessively is not acceptable

The thing to do when the guy comes for a look, is not to be argumentative, but be firm and express your concerns as to the quality, and "fitness for purpose". The firm is more likely to want to help a friendly customer

 

[Bilioustrumpstaine]

[quote="^woody^";p="1177469
The thing to do when the guy comes for a look, is not to be argumentative, but be firm and express your concerns as to the quality, and "fitness for purpose". The firm is more likely to want to help a friendly customer [/quote]

Absolutely the right approach, get the kettle on and the choccie hobnobs out.

You need to get this guy on your side.

 

[ratman123]

The boards should ideally be installed at 16% moisture content especially if they are T&G boards, this moisture content is somewhere in the middle of the lows and highs of moisture they will be exposed to during wet & dry periods (anything from 10-22%). Remember the treatment may be water borne and this can increase the moisture content, it wouldn’t be unheard of them not bothering to dry or re-dry them afterwards because it’s for a shed.

The tongues should also be about 8mm long minimum, as up to 3-4mm of movement (on a 150mm or less board) may still occur if dried properly and this helps them stay engaged with each other.

The above is recommend practice for cladding a building, and works well, but is often ignored when it comes to cheap sheds.

If the tongues are 8mm long, you can probably pull of the boards and refit them (replacing some of the warped boards), making sure not to tightly fit them back, but to only engage them halfway into the T&G. If the tongues are to short, then the risk is that if you refit them, when the re-expand in wet periods they may start bowing off as they will not have enough room to expand.