1st time building a deck (decking) advice.

Scotty001 · Post by **Scotty001** » Sun Jun 21, 2020 7:54 pm

Hi all, looking for some guidence.

I'm looking to improve the rear garden (4m x 7m) it's currently fully patio'd. I'm looking to build some decking 3.8m x 4m then lay fake grass for the remaining (all on top of the current patio)

There's a decent gradual slope to the patio, there's never been any pooling of water and all slabs are very even.

Due to the patio already in place I don't have the room for 150mm below the dpc to place the ledger. What I was thinking is placing the ledger as far down as pissible (to accomodade the decking bard closes to the cill of the patio door to sit just under the cill) and have about 15mm gap between the wall and ledger. Would it be possible to paint on some kind of sealant to a few courses of brickwork to negate any extra splashback from rain bouncing off the decking back onto the wall (or would doing this be detrimental in some other way to the structure of the building?

I also have an air brick right where the ledger would go, I'm looking to cut the ledger at one side of the air brick and place a 2nd smaller ledger the other side or the air brick, then use one noggin approx 200mm out from the air brick the connect the adjoining joists, do you think this would be adequate to keep good airflow for the air brick and keep a fairly good structure for the frame and joists?

Joists will be 400mm centers with noggins at 600mm intervals. The decking boards will have approx 8mm gaps between each board and the board closest to the wall I was thinking to be approx 20mm away from the wall?

Do you think that these dimensions and possibility of painting a sealent onto a couple of courses of brickwork would be safe to do and not cause any structural issues to the house?

Someone-Else · Post by **Someone-Else** » Sun Jun 21, 2020 8:24 pm

Regarding fake grass, have you got a dog?

Scotty001 · Post by **Scotty001** » Sun Jun 21, 2020 11:49 pm

someone-else wrote: ↑Sun Jun 21, 2020 8:24 pm Regarding fake grass, have you got a dog?

No, only a cat who seldomly goes out into the garden.

ahfix · Post by **ahfix** » Mon Jun 22, 2020 12:26 pm

how high above the patio will the decking board sit and what will be the clearance between the bottom of the joist and patio?

ah

Argyll · Post by **Argyll** » Mon Jun 22, 2020 2:32 pm

Photographs would be great mate

sammy.se · Post by **sammy.se** » Mon Jun 22, 2020 8:49 pm

I will just say that people, like myself, spend ages trying to remediate damp problems caused by a garden level that is too high, so just be cautious about preventing those problems... I'm not sure what options there are too prevent damp, smarter people than me will be along soon to comment

Scotty001 · Post by **Scotty001** » Sat Jun 27, 2020 4:30 pm

Sorry for late reply with pics (work has taken over a little bit this week

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aeromech3 · Post by **aeromech3** » Sat Jun 27, 2020 5:46 pm

My decking is at least 8yrs old, in a similar house to yours, fitted well before my ownership, it extends width of house and around to garage, concrete base is about 5" below top of deck and DPM is level with top, there is a minimal clearance between wood and house brick, air vents for suspended floor are below deck and there is no ledger board or hangars. Have not had any issues with damp back of house faces West. Full width picture is 5yrs old, have cleaned and regularly oiled the wood since. I have no idea what would be the problems if a heavy snow fall sits on the decking but would guess the warmth of the house brick would soon leave an air gap; just making it difficult to open the back door

Scotty001 · Post by **Scotty001** » Sun Jul 05, 2020 10:54 am

How does this plan look ?
in the plan i've drawn it up butted against the wall but the ledger wont be, there will be a gap of 15 - 20mm.
As the decking is going to be the same height as the DPC (as i dont have a 150mm clearance available) i was thinking of adding another decking board on its side to act as a splash back, the boards im looking at are 150mm width so if i stand it on its side so its protruding 150mm up from the deck (and 15 - 20mm) out from the wall im thinking it should act as a good splashback and limit the amount of rain bouncing off the deck and onto the wall which is above the DPC ?? what do you think ? would this option have better effect of preventing damp issues than if i just left the deck 15 - 20mm out from the wall ?

aeromech3 · Post by **aeromech3** » Mon Jul 06, 2020 11:11 am

IS THERE CLEARANCE UNDER YOUR NOGGINGS FOR WATER TO RUN DOWN THE SLOPE ?

Scotty001 · Post by **Scotty001** » Tue Jul 07, 2020 3:29 pm

aeromech3 wrote: ↑Mon Jul 06, 2020 11:11 am IS THERE CLEARANCE UNDER YOUR NOGGINGS FOR WATER TO RUN DOWN THE SLOPE ?

There is yes, the main frame, joists and noggins will be raised by 10 / 15mm from the patio surface using olastic adjustable joist risers with rubber footings and drainage holes in them too.

wes56 · Post by **wes56** » Tue Jul 07, 2020 6:49 pm

OP, looks like you have a suspended floor. the floor joists will probably be sitting in that inside skin and any cavity bridging will maybe cause wood rot.
The outside ground level is already too high and any deck will maybe bridge what looks like a DPC?
You only show one vent - there should be vents every 1.5m for a suspended floor, and the vents/airbricks should be fixed above the DPC.
Debris will form under such a low level deck.

You cant start rebuilding your house to install a deck but you should be aware of best practice.

Scotty001 · Post by **Scotty001** » Thu Jul 09, 2020 7:09 am

wes56 wrote: ↑Tue Jul 07, 2020 6:49 pm OP, looks like you have a suspended floor. the floor joists will probably be sitting in that inside skin and any cavity bridging will maybe cause wood rot.
The outside ground level is already too high and any deck will maybe bridge what looks like a DPC?
You only show one vent - there should be vents every 1.5m for a suspended floor, and the vents/airbricks should be fixed above the DPC.
Debris will form under such a low level deck.

You cant start rebuilding your house to install a deck but you should be aware of best practice.

The ground floor is a concrete base, there are 2 air bricks one either side of the patio doors.

keithski122 · Post by **keithski122** » Fri Jul 10, 2020 7:33 pm

I did similar to what your doing.The decking I built as a freestanding deck with the joist 10cm away from the house wall (and vent bricks) and the decking boards 10mm away from the wall.The deck goes under the bifold door sill and is above damp course.After 3 years I've had no problems with damp or splashback.Really pleased with how it went though if I was redoing it I would have 5mm gaps between boards instead of the 10mm I went with.

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Scotty001 · Post by **Scotty001** » Tue Jul 14, 2020 5:38 pm

In case anyone is interested I've completed my little decking project. It's taken me about 3.5 days which for my first timber build project I don't think is too bad.

I changed the decking build slightly and went for a free standing deck rather than using a ledger. (the weight of the deck is more than enough to keep it stable and planted firmly on the ground.

The deck is 3400x3400 & is level with the dpc, but it's 40mm away from the wall and I've fixed a piece of 2x2 pressure treated wood to the decking board then used some more decking board fixed on its side to give me a 150mm height splashback.
Where there are air bricks I've built in a box section so the bricks are not covered by a joist section. I've also got a small drainage manhole in the garden so I've built a box section around that for easy access (otherwise the would have been a joist running right over the top of it.)

All the frame timber and noggins are c24 treated joists using height adjustable plastic posts to raise the frame from the floor and give me a 12mm drop from left to right to aid water run off from the decking and have a gap between the frame and patio floor for any water run off below the decking.

The tools I used were a evolution rage 2 miter saw & dewalt 18v cordless drill / screwdriver, 8mm drill bit, 3mm drill bit and a countersink. The timber bolts and screws I purchased all came with the correct screwdriver bits to screw them in with. I also used 1L wood treatment on all the cuts to prevent and protect the sawn ends.