Decking/Pergola project - advice needed!

16 Feb 2005
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United Kingdom
Last couple of days we have decided to do something about our tatty looking patio, by placing some decking over it.

The space will cover the majority of the back of the house at 5.7m wide, going out to 2.7m.

In one corner we'd like to put a pergola up, in front of a window.

So, a few basic questions, with the pergola, I assume I can run a ledger plate across the wall above the window to use this for the cross member one end, and support the other with a ledger at the front with two posts.

This corner of the deck is over grass, so I had planned to dig this out, put down a layer of hardcore, then weed membrane. For the pergola posts, I have read a few places saying that they should be fixed in met posts or similar, but as long as fencing posts are used, surely they can be set in concrete just as you would a fence post?

Second point, where I have the grass area that will be dug out, can I just rest slabs on cement to match the level of the patio and so allow the frame to rest on it?

And then the frame, I have heard quite a few people suggest that the frame shouldn't just sit on the concrete, so that it won't rot with standing water. Where the frame needs to contact the patio for support, what should be used? Treated timber? Galvo plates?

With the length I will be running, if the boards run parallel to house, I will have to have joins. I'd rather not have joins, but if I run the boards outward from the house I can't see the frame being as easy to keep solid, unless I'm thinking about it the wrong way.

With the patio being sound but uneven, best way I see framework to be done is with a ledger plate bolted to brickwork below DPC, and then joists hung from this ledger running out the 2.7m length, with an end plate and any noggins necessary in between. The garden runs upwards from the house, but I would want the deck flat or at least running a way a bit, so realistically the joists will contact the ledger, then the end plate. So I will have to use posts or packing inbetween to support the framework.

If I wanted to run the board perpendicular to the house I'd be running the joists parallel to the wall, which if joists aren't available long enough, they'd need to be joined, and not tied in as well as running perpendicular from a ledger plate, so on the whole the first method sounds better, just accepting joints in the deck boards?

Does that sound clear as mud!!??

Ah, other thing, I'll be putting in some balustrading as well, should the newel posts be set into the ground (if above soil) or in met posts(if above patio), or are they screwed to the frame work?
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Started to plan it out, as I have 140mm below DPC I'll use 4x2 for the frame work at 400mm centres, joists running outwards from the house from ledger plate, just below DPC. Is it OK for deck board to be level with DPC, as long as it and the ledger are spaced from the wall?

Next question I have is for a 2.7m span at 400mm centres, what spacing of noggins should I use? I have seen aything from 400mm centres to 1.2m centres advised.

Also, for supporting legs of framework, I have been advised 1.5-2.0m spacing for 4x2. Does that sound right?

Thanks in advance :)

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