Pond filter cover

[Roger Mills]

At the end of my pond there is a small brick-built enclosure which houses a filter and air pump. I need to make a new lid for it because the current one (about 7 years old) is past its best. When new, it looked like:

max dimension are 1400 x 900, and it is rounded at one end and cut off at an angle at the other end. It's currently made out of a piece of board [1] which is covered by roofing felt - which is folded under and stapled on the underside. The board is getting to be decidedly soggy, and needs to be replaced.

Any suggestions as to what to use as a replacement. It needs to be heavy enough not to blow away, but light enough for me to lift off. It needs to be able to survive the weather. I've got some more roofing felt with which I can cover it if necessary, but the current one seems to get wet on the

*underside* for some reason which I can't fathom. SWMBO suggested using a slab of marble(!) but that's likely to be (a) expensive, (b) difficult to cut to shape and (c) too heavy to lift.

Any (sensible!) alternative suggestions?

TIA.

[1] There's probably a proper name for it, but it's the sort of board often used for shed roofs - a bit like chipboard, but made from wood shavings rather than chips

[Andy Dingley]

I'd use Viroc Versapanel, which is some sort of cement-based MDF and works great for fascia boards and the like. It takes paint (cement tolerant paints) but lasts well without it. It's about as stong as MDF

- I wouldn't walk on it, but thick slabs of it would probably be OK. Drills easily but doesn't take screwthreads.

Wickes have their own version, and there's Aquapanel too which costs more but is available in small pieces.

[The Wanderer]

How about a self-built GRP lid? I was thinking of something similar to the protective coatings offered as a 'cure-all' treatment for flat roofing.

If you can find a resin supplier near you, they would probably be able to help with suggestions about suitable materials. (Somewhat messy memories from quite a few years back of making a GRP kayak for son when he was in the Sea Scouts!)

Also has the advantage that you can add pigments to the resin to get a suitable colour for the garden.

If you've any nearby, it's also worth trying any boat builders in the area to source materials, given that you're not going to need a lot.

Condensation?

[Dave Liquorice]

That might be a mistake water on the top will run around and make it's way onto the board. It would be better to fix the felt with fixings into the board edge and left the felt hang down an inch or so.

Does the board rest on top of the bricks all the way round? Is there any decent ventilation of the enclosed space. I suspect condensation. Lift the board 1/4" or so above the bricks to allow air to circulate and dry any condensation. With a decent hanging lip of felt nothing significant will blow in.

The board you have is Oriented Starnd Board (OSB) it's not overly waterproof. I'd go for 18mm WBP (Water and Boil Proof) ply. Nice bit of weight and won't object to a getting wet.

[Roger Mills]

[I'm back on the case, having been away for a few days]

Thanks for the suggestion. I've not come across Versapanel, but it sounds like it might do the job. Are BMs such as Jewsons and TP likely to stock it?

I'm also considering making a small lean-to tool shed, because none of the plastic affairs stocked by the 'sheds' is quite the right size/shape. If I make a wooden frame, would Versapanel be a suitable material with which to clad it?

[Roger Mills]

I'm more inclined to think that it's condensation. Loose bits of felt hanging down would make the board very difficult to move without damaging the felt.

It rests on bricks most of the way round but there are gaps on the pond side for pipes etc. to pass through, so there's *some* ventillation.

Lifting it may be an idea, but - as above - I don't like the idea of hanging felt.

Thanks - I wondered what it was called

That sounds possible. Where would I get that?

[Dave Liquorice]

True enough but how often does it need to be moved?

Through ventilation or just small gaps around the pipes? I doubt the latter would do the job of shifting condensation as there isn't going to be a through flow of air.

Any decent builders/timber merchant. I'd be a bit wary of the DIY sheds unless the sheets are marked as WBP or similar spec. Just plain unmarked sheets could be anything.

[Roger Mills]

Several times a year, in order to clean the filter and/or replace it with a by-pass pipe in the winter to keep the water feature going.

Thanks - I guessed as much. I've rung a couple today - and they're talking about £25-ish +VAT for an 8 x 4 sheet of 18mm WPB. Does that sound about right?

[I haven't yet found any local stockists of Versapanel - which someone else suggested.]

[PeterC]

That's about the same as I paid in Wickes last year.