Using cement fibre board as exterior cladding?

[scott08]

I've built an outbuilding, and am in the process of cladding it now. It's concrete block all round (had to incorporate a retaining wall into it), which i've battened and clad with timber on half of it. On the other half, down the fence side, I can't bring myself to spend the massive cost on charred timber (like the rest of it) for a side that isn't very visible.

Trying to think of the cheapest cladding solution that also doesn't look terrible - could I use cement fibre boards, edges sealed with silicone, painted in something like black zinsser all coat? This would be on top of battens fixed to the concrete block, leaving a continuous airgap of 25mm, vented top and bottom. Something like this:

2.4m Fibre Cement Backer Board for Construction, Exterior Grade

<h2>Discover Fibre Cement 2.4m Multipurpose Backer Boards</h2> <p>Whether you are looking to board walls or floors (pre-tiling), fibre cement boards can make this job much easier. 2.4m lengths boards can be used on ceilings, around fires, internally and externally.</p> <p>Due to being a...

www.cladco.co.uk

Any reason this wouldn't work, or any better similar priced options would be great to know.

 

[23vc]

Coroline black corrugated sheets can look decent fitted vertically. And dead cheap.

 

[^woody^]

Cement sheets will do, but be prepared for regular repainting.

Also if these will be seen, instead of just banging up some 8x4 sheets, consider cutting the sheets down into smaller modular sections and making a vertical or horizontal design.

Edit

Have a look at MgO boards, they are a lot cheaper than the typical Supalux or similar silicate product

 

[aveatry]

How robust are they. My experience with undercloak for roofs - all be it much much thinner is that they are very brittle

 

[^woody^]

They are robust but need suitable support every 400-600mm and at the edges to stop any flexing. The OP will probably need something thicker than 6mm undercloak

 

[yorksbuilder]

Coroline black corrugated sheets can look decent fitted vertically. And dead cheap.

Poor impact resistance and fire hazard

 

[yorksbuilder]

Any reason this wouldn't work, or any better similar priced options would be great to know.

Should be fine. I clad a wooden outbuilding in no more ply and painted it with basic Screwfix no nonsense outdoor paint. Looked great.

The no more ply 8x4 sheets are used to clad buildings and then get rendered. But the paint you mentioned would be fine. Just keep up the maintenance, probably need repainting now and then

 

[aveatry]

Poor impact resistance and fire hazard

I have them on my shed and are quite strong - talking about impact resistance from new i can stand on then without squashing the ridges but not in the middle of summer and they are about 10 years old now and from frequent climbing on them they are starting to need replacing but on the side of a building I would think they would be fine but not from the fire risk

 

[scott08]

Cement sheets will do, but be prepared for regular repainting.

Also if these will be seen, instead of just banging up some 8x4 sheets, consider cutting the sheets down into smaller modular sections and making a vertical or horizontal design.

Edit

Have a look at MgO boards, they are a lot cheaper than the typical Supalux or similar silicate product

That's a good shout, I can cut the big sheets down to thirds and have long vertical strips. How often is regular for the painting? The roof has a slight overhang and there's a fence next to it, so shouldn't get battered with the weather. I may even put a bit of trellis on top of it and allow some plants to partially cover.

Would the MgO boards perform the same as cement boards outside?

 

[scott08]

Should be fine. I clad a wooden outbuilding in no more ply and painted it with basic Screwfix no nonsense outdoor paint. Looked great.

The no more ply 8x4 sheets are used to clad buildings and then get rendered. But the paint you mentioned would be fine. Just keep up the maintenance, probably need repainting now and then

Good to know - how has the paint held up for you/ have you had to repaint? Any pics of it would be great, I can't fully visualise what it would look like

 

[^woody^]

Would the MgO boards perform the same as cement boards outside?

They should do, but refer to the specific manufacturer's guidance for the board.

 

[freddiemercurystwin]

Are any of these boards actually approved for long term external exposure without any further treatment or covering with something?

 

[cdbe]

I haven't bought any for a while but I don't recall box section metal sheets being that expensive and you can usually pick up small quantities on eBay/marketplace.

 

[yorksbuilder]

Good to know - how has the paint held up for you/ have you had to repaint? Any pics of it would be great, I can't fully visualise what it would look like

Moved out of that house now but it was still like new after a couple of years when I moved. Would differ depending on exposure to sun/rain etc

 

[scott08]

Are any of these boards actually approved for long term external exposure without any further treatment or covering with something?

Not as far as I know. But then I would be painting it with an exterior paint, so this should mostly weatherproof it