Roof painting tips .

[Greg & Jax]

Hi all .

I'm looking for tips on painting  my roof .

I'm about to scabbler my roof  to remove rust  under the paint but  after doing some research into painting I'm not sure  about the primer as it's porous  

I don't have the luxury of a paint shed so will have to paint the roof outside albeit under cover .

Is there a non porous primer I can use so I can paint the top coats at a later stage ? 

Any help would be great . 

Regards Greg. 

[Bee]

Ordinary primer will be ok if left for a short while, I would paint it with top coat after 24 hours or so. Give it 2 or 3 coats over the course of a week so you don't have to keep sanding it back. to get a decent thickness. The roof has a hard life.

[Greg & Jax]

Thanks bee .

[stegra]

My boat was two pack primed when new. The deck areas are still in primer two years later with no ill effect. Can't help with the brand of paint, unfortunately. 

[Greg & Jax]

Thanks stegra. 

 I will look into that cheers .

Greg .

[Greg & Jax]

Hi guys .

There will be about a week between the primer and the top coat where the boat will not be under cover so open to be rained on  . Is this be ok ? .

Cheers Greg. 

[Dr Bob]

Primers are normally porous for a reason.

They tend to be thinner than top coats so they wet the surface well for ultimate adhesion and the tend to have a lot more filler in ......hence the porosity........so they can be sanded to give a very smooth finish, filling in the irregularities of the steel, prior to the top coats. We have had our roof painted this winter and they put 5 coats on to get a nice finish.

You can use two pack coatings direct to steel but they will be a pig to sand and so not going to be easy to get a nice final finish. If you want a two pack, look for an epoxy deck coating...i.e. an anti slip flooring coating. They can go direct to steel but best get rid of the rust though. Best over grit blasted steel.

Can you leave a primer for a week without overcoating? Yes......but best to do that when the weather forecast is predicting a reasonably dry week....i.e. Not this week!

 

[Greg & Jax]

Thank you for the reply Dr Bob. 

That's makes things a little clearer for me . 

I will be able to get three coats of primer on under cover then the week after a light rub down and start the top coats . 

Cheers . Greg. 

[Richard10002]

2 hours ago, Greg & Jax said:

Thank you for the reply Dr Bob. 

That's makes things a little clearer for me . 

I will be able to get three coats of primer on under cover then the week after a light rub down and start the top coats . 

Cheers . Greg. 

Why not get two coats of primer and one of undercoat? I understand that undercoat is not as porous as primer. I left my roof with 2 coats of undercoat over one winter then one more undercoat in Spring before 2 topcoats. All looks fine a year or so later - we shall see  

[zenataomm]

You never actually paint a boat … you merely lend it some for a short time.

[Greg & Jax]

Thanks for the info guy,s .

I didn't realise that the undercoat wasn't so porous. 

Thanks to the tips here my roof will be a lot more manageable. 

Thank you. 

[AndiKH]

My roof needs doing ASAP but there are massive flakes of rust chipping off... how can I fill these patches and what with? TIA

[WotEver]

48 minutes ago, AndiKH said:

My roof needs doing ASAP but there are massive flakes of rust chipping off... how can I fill these patches and what with? TIA

Wire brush off the worst, treat with Vactan or similar, and then if you really want to fill the spots use a 2-pack car body filler. 

[Chewbacka]

12 minutes ago, WotEver said:

Wire brush off the worst, treat with Vactan or similar, and then if you really want to fill the spots use a 2-pack car body filler. 

Or don’t bother with the filler and accept it as part of the boats character and history?

[AndiKH]

Thanks very much! It's my first boat, it's daunting but I'm determined to do it myself

 

[WotEver]

2 hours ago, Chewbacka said:

Or don’t bother with the filler and accept it as part of the boats character and history?

That would certainly be (and was) my approach. 

[jacko264]

Primer is a etching paint to eat into the steel you will only need one coat  the next thing is the under coat that gives the top coat(  gloss ) it's body  and two coats is better then one  the water proofing is the gloss and the finishing cover 

and don't forget to give it a rub down with 240  wet and dry paper between each coat to do it right it should have 24 hours between coats

jacko

[Dr Bob]

11 minutes ago, jacko264 said:

Primer is a etching paint to eat into the steel you will only need one coat  the next thing is the under coat that gives the top coat(  gloss ) it's body  and two coats is better then one  the water proofing is the gloss and the finishing cover 

and don't forget to give it a rub down with 240  wet and dry paper between each coat to do it right it should have 24 hours between coats

jacko

Primer is not 'etching' and does not eat into the steel.

It is formulated to fully wet the surface and adhere well. Yes you only need one coat of primer.

[jacko264]

Well you learn something new every day ? It defanetaly says etch  primer on the paint we use at work for painting buses 

they are hand painted with rollers and brush 

jacko???

[Mad Harold]

1 hour ago, jacko264 said:

Well you learn something new every day ? It defanetaly says etch  primer on the paint we use at work for painting buses 

they are hand painted with rollers and brush 

jacko???

In a different life I was involved with aeroplanes and the aluminium ones were painted with etch primer.This was a greenish yellow colour and mixed with a clear liquid which was the acid.It actually ate into the metal slightly and was permanent.

I hav'nt seen it used on anything other than aircraft, but an other poster says it'used on buses.

[Dr Bob]

12 minutes ago, Mad Harold said:

In a different life I was involved with aeroplanes and the aluminium ones were painted with etch primer.This was a greenish yellow colour and mixed with a clear liquid which was the acid.It actually ate into the metal slightly and was permanent.

I hav'nt seen it used on anything other than aircraft, but an other poster says it'used on buses.

Yes, that's for aluminium, not steel. Primers for steel don't eat into it hence you don't get etching primers for steel boats.

[jacko264]

Ok I submit we do use it on aluminium but we also use it on steel and it works well on both

some of the old buses have steel panels??

[WotEver]

1 hour ago, jacko264 said:

Ok I submit we do use it on aluminium but we also use it on steel and it works well on both

some of the old buses have steel panels??

It may work on on steel but the point is that it won’t be etching the steel. Because, well, it’s steel, not aluminium. 

[jacko264]

Ok  after repairing and painting buses for 28years  the paint we use does a fantastic job

and maybe I should not have used the word etch and just said primer  

jacko

 

 

Edited August 2, 2019 by jacko264

[blackrose]

Bonda Primer isn't porus. It looks just like red oxide but it's much better.

 

https://www.sealantsonline.co.uk/product.php?product=BOND009&category=00320013&utm_source=google&utm_medium=products&gclid=Cj0KCQjwvo_qBRDQARIsAE-bsH9rNDk2BRw8pYnfV0sCQPfP7Vt_t4KNC3mWATXNQlNQSUr7diZe7o4aAjHzEALw_wcB

 

Whatever primer you use don't put your top coat straight onto the primer. You should use a good quality undercoat between the two. 

 

https://www.paintmarine.co.uk/hempel-primer-undercoat-paint-47368-p.asp?_=&variantid=47369&gclid=Cj0KCQjwvo_qBRDQARIsAE-bsH-e2NyIc_n6lv0-G4Fkp0W8B2fxK7lX4dSdVq1sWJXiY-KNqR0_76EaArfxEALw_wcB

 

If you can get subsequent coats on within 2-3 days you don't need to key, otherwise you do to ensure good interlayer bonding.