Marine paint for (non-marine) extrerior wood?

[Steve_Bentley]

Okay, non-boaty, but I'm someone out there can help!

I have a softwood framed conservatory which cost a fortune to build and I want to preserve it at almost any cost. Anway, two areas keep getting rot and as they're structural (posts) I can't afford to keep chopping out wood and replacing. I've been using Dulux Weathershield range of rot-proof (ho, ho) primer, undercoat, top coat and basically it's not keeping damp away from the wood. It gets repainted every 2 or 3 years.

I 'm now thinking of trying some marine paint, perhaps epoxy, to permanently seal the rain out, at the very least at the bottom of the posts. Can anyone here suggest something suitable? I'm thinking if it's good enough for a wooden boat it's got to be the best option?

Thanks in advance!

 

[Blueboatman]

Its rotting cos the water is getting in to the joints or open grain and remaining there !
If you cannot remedy that I would dry it out and apply liberal coatings of cuprinol.
Adding lead flashings can help too as can rebedding dodgy joints/glazing bars but that means a certain degerr of dismantling.
There is no wonder marine-paint cure I am afraid.In fact overpainting damp will exaserbate(sorry cant spell) the rot by trapping moisture.
Post a piccie if you like to get specific ideas.
EDIT Conservatories can rot from the inside out too if there is high humidy and no ventilation.

 

[Steve_Bentley]

Well, my theory is that the epoxy/whatever would seal all those gaps-n-cracks where the damp is getting in. Unfortunately one of the posts seems to be soaking up the water like a sponge. Shame we've had such a wet summer. International do a waterproof aluminium primer (non-marine range) I'm toying with. I'm also thinking epoxy would soak in to the wood whereas the Dulux stuff sits on the surface (until the blisters pull away!).

 

[MoodySabre]

If the wood is getting soft then you could, once it is completely dry, treat it with wood hardener from any diy shed. You give it a good soaking and it dries really hard like a resin and seems to be waterproof. It has stopped the bottom of the frames on an external door from swelling up each time it rains.

To stop the next bit from getting the damp then some preventative flashing etc as suggested would be a good idea.

 

[Steve_Bentley]

Hmmm, hadn't though of wood hardener- worth a look, thanks!

 

[dickh]

You should use a 'breathable' paint - we use Jotun DemiDekk and you will only need to clean and repaint every 5/6 years. The only downside is that it's not glossy, only matt but I don't find that a problem.

 

[mortehoe]

Several spefications:

Option 1) Strip all the paint off back to bare wood from the affected areas and to at least 200mm to all sides around the affected areas. Cut out all rotted wood that is soft. Apply 3 coats of exterior solvent based wood preservative. Apply two coats of wood hardener. Fill all voids/cracks etc with resin based exterior wood filler in layers to build the voids depressions etc back to the original size. Knot/stop any knots. 1 coat all purpose primer. 2 undercoats. 2 topcoats of flexible gloss. (remember to sand lightly down between each coat of paint and clean with a tack cloth. )

Follow the manufacturers instructions to the letter especially re overcoating times.


Painting with marine paint alone is no good. Rot is caused by the paint cracking at arisses/coins allowing moisture to get in behind the paint and raise the water content of the wood to ~20-30%. It sounds as though you are getting wet rot which is far better than getting dry rot! (Still a bad thing!)

Option 2) Find out exactly what is moving to cause the paint to crack. Correct the movement issue if you can. Clean out the cracks with acetone/keytone and fill them with exterior grade flexible non-setting mastic. Wait and watch to see if rot restarts.

Option 3) Take out the untreated structural posts and replace them with clearwood tanalised posts. This would mean that if you could do this, then those posts would have a rotfree life possibly greater than 60 years.

Option 4) .... A total rebuild from scratch using methods and materials that comply with Building Regulations requirements.

 

[Niander]

[ QUOTE ]
You should use a 'breathable' paint - we use Jotun DemiDekk and you will only need to clean and repaint every 5/6 years. The only downside is that it's not glossy, only matt but I don't find that a problem.

[/ QUOTE ]


How can that let water only one way?

 

[blackbeard]

and before anyone else says it, don't use yacht wood primer (at least not near anywhere children could possibly reach), it contains lead! (amongst other things).

 

[Egbod]

Hi
I have had a similar problem with wood window frames and a wood conservatory frame in the past.
My solution is to drill some holes into the affected areas and for a distance beyond that- into sound wood, I also did around other joints that weren't rotten (yet). The holes must slope downwards slightly and go in quite a long way. I then fill the holes with Cuprinol 5 star timber preservative. This is a high quality preservative and treated wood can be painted later. Beware lots of the timber preservatives cannot be painted over afterwards. The Cuprinol 5 star soaks into the wood- top up the holes again and again over several days. I use a small syringe which fits into 6mm diameter holes. Then let the wood dry out for a few days, fill the holes with an external grade filler- I used epoxy filler, sand and paint over again.
The Cuprinol 5 star is available from many DIY stores, I found that a 5 litre can cost little more than a smaller can. It is not cheap but is very good stuff and has worked very well. No I do not have any connection with the company. Good luck.

 

[neilmft135]

If your not to bothered about the color use creosote & waste oil from a diesel engine 50 / 50 mix have used this on windows, doors, roof surounds, for years, very fast to put on any spills on the glass wipe with cloth only draw back smells bad for a few days. hope this helps.

 

[Pasarell]

Some good advice already and some, IMHO, rather more dubious.
If it's softwood it won't last forever but it should last a good time. It will take up water unless you can form a perfect seal around it - almost impossible.
You won't get epoxy to stick to it with any real success as the moisture in the wood will push it off and it will crack as the wood moves.
Best thing is to soak the wood as much as possible with a good solvent based wood preserviative such as Blackfriar or Cuprinol 5 Star. Make sure it is clear and not pigmented and never bother with water based "preservers"
Coat with a good quality primer containing aluminium flake such as International Metallic Grey followed by good quality gloss. Undercoat as well if you want. Always use at least 2 coats of each and more of the gloss if you want as it will increase longevity. Follow overcoating instructions carefully and stir the paint properly with a wide flat stirrer - especially the primer.
As mentioned elsewhere the endgrain is the most vulnerable to breakdown so pay most attention here. You can use a flexible mastic on joints if you want but it is unlikely you will make them fully waterproof and a wider gap will dry naturally more easily than a narrow one.
Good marine paint is generally better than domestic products and you get what you pay for, especially with the primers which are the most important part.
If you already have water in the wood you may be best off with microporous paints rather than all the work above. Unfortunately there are some exagerated claims made about these paints. Still use the wood preserver first and only apply 2 coats of paint - this is a case where more coats are a bad thing. You will need to clean / abrade and apply another coat every couple of years.
Lastly, if you've already got rot in the wood, you need to cut it out well back into sound wood and replace. Hardeners are alright but they only mask the problem for a while, not cure it

 

[Grajan]

No point in applying Epoxy coatings if you have been applying Timber preservative as they do not complement oner another
Clean back and use a Sikkens or Sadolin product designed for the job.
Yacht paint systems would involve at least seven coats of paint and even then you could have detachment problems due to incompatability with whatever chemicals are already in the timber
PS Lead has been banned in marine paint coatings for many years now

 

[steve_cronin]

Dulux Weathershield Gloss IS your problem.

We used it on our office windows a few years ago and on our remaining wooden bits at home.

Result: Although the surface gloss has been retained, ALL of the painted frames have succumed to rot. The pasint seems to hold water in and allow pockets of rot to start and as you've found. that is the beginning of the end. I will NEVER use it again.

Steve Cronin

 

[Steve_Bentley]

Thanks everyone!

Thanks everyone for taking time to reply with some good suggestions. As I'm writing the hair dryer is blasting away (might use the heat gun later)!

I'm not using Dulux again as I agree it seems to trap the water behind rather than sealing it out. I've seen some Sadolin paint yesterday (expensive) that might be breathable?

I'll try drilling the holes and soaking. I have been using Cuprinol clear stuff (not sure if it's the 5-star label), but preferable to the Dulux equivalent which was originally used.

I've bought the International 'high performance' metallic primer, and Cuprinol hardener.

The conservatory is south-facing and it can get a battering from coastal winds so I don't think i'll ever stop expansion/movement/flexing cracks, so I'm stuck with the usual gamble whether sealing is going to trap moisture in or keep it out!

I though I'd read that epoxy ('w.e.s.t.'?) can soak into the wood and I thought that would help form a permanent, strengthening, barrier- but there doesn't seem much support for that theory.

Thanks everyone- I'll report back after the winter!

Cheers,
Steve

 

[LittleShip]

Re: Dulux Weathershield Gloss IS your problem.

Weathershield is a 3 coat application..........

1. Primer
2. Undercoat
3. Topcoat

Used correctly it is by far the best weather prevention paint system around.
Used incorrectly and you have just wasted your money.

Tom

 

[steve_cronin]

Time hasn\'t proved to be on your side on that one me old son.......

and this crap: http://www.dulux.co.uk/products/info/usage/weathershield_exterior_gloss.jsp
just looks like a cop out.

Of COURSE we used a proper paint system!

Steve Cronin

 

[Grajan]

All paint finishes are porus to one degree or another, even Epoxy!!
wood hardeners although supplied in a single container can be based on two pack polyurethane, with moisture being the curing agent, these products work very well but timber must be dry and free of timber preservative to allow the product to soak in before atmospheric dampness starts the curing process
Good Aluminium based primers are very efective as this type of coating allows microscopic breathing and slows down water ingress due to the the overlapping of the leaf aluminium within the paint film however the manufacturers instructions MUST be obeyed to the letter otherwise you will have top coat detachment

 

[cliffordpope]

I think you have to make the choice between appearance and longevity. In my experience all paint causes rot - it traps moisture. the only way to stop wood from rotting is to keep it dry. If that can't be achieved then the next best thing is to soak it in preservative, the cheapest and nastiest the better (creosote, stockholm tar), whenever the wood does dry out.

Look at old ruined houses - bare neglected window frames last a hundred years. Well maintained painted ones rot after 5 years.

 

[Thistle]

Re: Marine paint for (non-marine) exterior wood?

I note the helpful replies re paint / preservative etc. An alternative solution which may be applicable in some situations is to replace the sections of wood which are prone to stay wet and then rot with a material (metal / brick / stone / plastic / ...) which is less readily damaged by water.

For example, if the end of a post sits in a damp area, think about cutting away the bottom few inches and replacing with a galvanised and painted leg which is strong enough to support the structure. Design the leg and its fixings to minimise the number of places which can collect and retain moisture.