Joint Preparation for Blueboard wall

[pfuller]

I've just constructed a 4.8m X 2.4m wall frame for an outdoor feature wall out of treated pine. I'm thinking of attaching blueboard to the frame, but doing my research on this forum, I hear that its almost guaranteed to move and the joints will appear through the paint/render in around 1-2 years time.

What is the secret to preparing the joints so they wont show up over time? Should you leave a small gap between the vertical joins to allow for movement? Or butt them together tightly?


Can anyone suggest any alternatives to blueboard? If blueboard is my best option, what are some good quality products to texture/render with so screwholes/nail holes and joins wont show?

Are clouts or countersunk galv screws best for a treated pine frame?

Please excuse all the questions, but the web seems very light on in information regarding blueboard installation and rendering. Any websites anyone know about would be appreciated.

[Dirty Doogie]

Generally I leave a few millimetres gap between the sheets and underfill it with polyurethane sealant. If the sheets are exposed to the weather at the back of the sheets you are going to get lots of movement in the sheets. I would seal the back of the sheets with a waterbased bitumen type coating before installing them .

In my experience the best joint finishing products where movement is likely are the acrylic based products (or bitumen products). They will come premixed in drums. The system I have been using is a Rockcote system - but it is not available everywhere.

This system requires the sheets to be resealed using a primer, then a patch and reinforcing bandage along the jions, then a smooth sandable patch for final finishing on jions and nailholes. THEN - (yes it is tedious) after sanding the patched areas are reprimed and a flat acrylic based colored render coat is rolled on.

Another easier finish is to use Bituminous waterproofing as joint filler and texture coating. The product I have been using is Bit Kote #3 and is available nearly everywhere (bunnings standard stock line).

First seal the gaps between sheets with Acrylic Exterior gap filler then prime entrie sheet with a 50% diluted coat of Bitkote. To patch the jionts and other holes mix up prebagged mortar and 25% dilution Bitkote into a thick paste and trowel into the recesses- press joint tape into the wet surface and try to finish joints as smooth as possible becuase this mix wont sand.

When this is dry apply a layer of neat bitkote over seams and corners and press some reinforcing bandage over the seams and around the corners , into the wet bitkote - then cover with more bitkote. When dry you are ready to texture coat. Simply apply bitkote wuth a textured roller to desired texture (Do this in shade) - then paint with a flat /low sheen acrylic.

The advantages of the Bitkote are that it is flexible and cracks wont happen , and it is cheaper than acrylic systems (you'll need 2 20 litre drums for your size job - $180) - the disadvantage is that you need finishing skills to get a smooth level surface (ie it cant be sanded back).



For a good result with any product it is necessary to fix the sheets as bracing sheets - which means more fasteners at closer spacing. I would also cover and finish the top of the wall with blueboard and coating to stop water entering the frame during rain.

[pfuller]

Thanks Doogie. I haven't heard of bitumen being used as render before, but the flexiblity and waterproofing qualities makes it seem like your onto a good system.

The only thing that worries me is the finishing and texture that it will allow? Can you get a nice texture into it? Should you reroll with a texture roller after its semi-dried or will it hold its texture straight from the bucket while wet?

When you say:

"prime entrie sheet with a 50% diluted coat of Bitkote".

What do you dilute the bitkote with?

[Dirty Doogie]

The Bitkote dilutes with clean water. The textures you can achieve are limitted only by your time and skill. You can throw fine or course sand into a basic rolled coat to get a sand blast finish.

Texture rollers come in several grades - I have been using the course texture sleeve. The wet bitkote will tend to run and slump down initially when put on with a course sleeve - it is only a matter of re rolling over each section as it stiffens up, to get the finish you want.

In the next couple of days I'm going to be doing the bitkote texture thing as well as bandaging jions etc on my letterbox and if you like I could post step by step pics and examples of texture coating for you. It is looking a lot like rain right now though.

[Dirty Doogie]

Here is an example of the texture that can be achieved - this is a corner that has been filled, bandaged then carefully roll coated. Hope the pic shows the detail.

[Dirty Doogie]

Incidently the substrate sheeting used here is 4.5 mm thick durasheet nailed to timber - care was taken to make corner jions a neat fit. The acrylic filler can often sink down as it dries and leave a little line if the gap is too big. Generally if you have to fill big gaps you would wait a few days and refill with more acrylic gap filler.

[pfuller]

Looks great doogs. Any pics you could send while your doing the job would be appeciated.

[Bloss]

Just visit here - it tells all.

http://www.jameshardie.com.au/Produc...em/TechManual/

and

http://www.jameshardie.com.au/NR/rdo...mentJoints.pdf

[Dirty Doogie]

A week later and i still havent done any texture coating LOL.

[pfuller]

haha..well..either have I!

I have decided to use MacPatch Coarse though to patch the joints, and over coat that with MacTexture Trowel on, which comes as a coloured finish. This is one of the best options i could find. Others require more coats of primers and membranes etc. This system really does too, but seems like i can get away with a patch of the joints, a skim using the same product (Mac patch coarse) and a finsihing coat just by using the texture trowel on. Works out the most cost effective way i could find.

Your bitumen solution propbably works out cheaper, but i couldn't find out enough about using bitumen on blueboard, so wasn't confident using that method.

I'll hopefully get my joints done this weekend.

[pfuller]

Thanks for the links Bloss!