Subfloor Repairs Sydney

Subfloor repairs Sydney work from Probuilding & Carpentry: rotten, termite-damaged or undersized bearers and joists replaced, timber floors re-levelled and the cause of the damage fixed, by a licensed NSW carpenter based in Peakhurst.

A springy floor, a sloping hallway or a door that has started to stick is rarely a floor problem. It is a subfloor problem. Somewhere underneath, a joist has rotted at the bearing, a bearer has sagged between piers, or a stump has dropped. By the time you can feel it, it has usually been happening for years.

We get under the house, find out exactly what has failed and why, and fix the structure properly. Not a few packers and a quick sister joist, but timber replaced to the right size, supported on something that will not move, and with the moisture or ventilation problem that caused it dealt with so it does not happen again.

What Our Subfloor Repair Work Includes

• Subfloor inspections to find what has failed and why
• Bearer replacement, including temporary propping of the floor above
• Floor joist replacement and sistering of damaged joists
• Replacement of rotten or termite-damaged subfloor timbers
• Packing, re-supporting and re-levelling sagging timber floors
• New piers, stirrups and ant caps where the supports have failed
• Subfloor framing under bathrooms and laundries damaged by leaks
• Improving ventilation and clearance so the new timber lasts

As licensed carpenters, our subfloor repairs Sydney clients get structural timber work done by the same people who build new subfloors for decks and extensions, so the repair is built to the same standard as new work.

Subfloor Repairs Sydney: Signs Your Subfloor Needs Attention

Most people call us because of something they notice inside the house. These are the common ones, and what they usually point to underneath.

• Bouncy or springy floors. Usually joists that are rotten at the ends, undersized for the span, or have lost support at a bearer.
• Sloping or uneven floors. Often a bearer that has sagged between piers, or a stump or pier that has settled.
• Gaps under skirting boards. The floor has dropped away from the wall as the framing below has moved.
• Doors that stick or will not latch. The floor and frame have moved out of square.
• New cracks in plaster or cornices. Movement in the floor is being transferred up into the walls.
• A musty smell or damp air under the house. Poor ventilation and moisture, which is what rots subfloor timber.
• Mud tubes on piers or timber. A sign of termites, which need a licensed pest controller before any repair.

Any one of these is worth an inspection. Catching subfloor damage early usually means replacing a few joists rather than a whole section of floor.

Bearers, Joists and Stumps: What Each Does

Knowing what each part of the subfloor does makes it easier to understand a subfloor repairs Sydney quote and why one repair costs more than another.

Timber Floor Joist Replacement

A damaged joist can be dealt with in two ways, and the right one depends on how much of it is still sound.

Sistering

Where a joist is mostly sound but has a damaged section, a split, or is slightly undersized, a new full-length joist can be fixed alongside it. This is quicker and less disruptive because the floor above does not have to come up.

Full replacement

Where a joist has rotted through, has extensive termite damage, or the bearing ends have failed, it needs to come out. We support the floor, remove the old timber, and fit a new joist of the right size and grade, properly fixed at each bearer.

On a timber floor joist replacement, we also check the joists either side. Rot and termites rarely stop at one piece of timber.

Bearer Replacement Carpenter Sydney: How We Replace Bearers

Bearers carry far more load than joists, so replacing one is a structural job. Done badly, it can crack walls and ceilings above.

1. Temporary support. Adjustable steel props go in either side of the bearer to carry the floor while it is out.
2. Removal. The damaged bearer is cut out in sections, so the floor above is never left unsupported.
3. Supports checked. Piers and stumps under the bearer are checked and replaced if they have failed.
4. New bearer. A new bearer, sized to the span, goes in on ant caps and is packed to level.
5. Joists re-fixed. The joists above are re-supported and fixed, and the props are removed gradually.

Subfloor repairs Sydney homeowners can trust are done in this order every time. It is slower than jacking a floor and packing it, but it is the version that lasts.

Why Sydney Subfloors Fail

Replacing rotten timber without fixing the cause just means doing it again in a few years. The usual causes are the same across most Sydney homes.

Poor ventilation

Subfloors need air moving through them. Blocked vents, garden beds built up against walls, and extensions that closed off airflow all trap moisture under the house.

Low ground clearance

Timber sitting too close to the soil stays damp and is easy for termites to reach. Many older homes and add-ons were built with less clearance than they should have.

Water getting in

Leaking showers, failed waterproofing, burst pipes, downpipes that discharge against the house, and poor site drainage all put water where the timber is.

Termites

Termites thrive in damp, poorly ventilated subfloors. Termite activity needs to be treated by a licensed pest controller before the damaged timber is replaced.

Past repairs and renovations

Joists notched for plumbing, bearers cut for a new opening, or piers removed during an earlier renovation are common finds.

Part of every subfloor repairs Sydney job we take on is pointing out which of these caused the damage, and what needs to change so the new timber does not end up in the same state.

What Affects Subfloor Repair Cost in Sydney

Subfloor repairs Sydney pricing depends far more on access and the extent of the damage than on the timber itself.

• Access and crawl height. A subfloor you can kneel in is much faster to work in than one where you have to lie flat.
• How far the damage has spread. Two joists is a very different job from a full bearer line.
• Whether the floor above has to come up. Working from above is sometimes the only safe way, and adds flooring work.
• Supports. Replacing piers or stumps adds footing work.
• The cause. Ventilation, drainage or plumbing fixes that stop the damage coming back.
• Re-levelling. Bringing a floor back to level after years of movement takes time to do properly.

We price on what we find under the house, with the work itemised. If you are budgeting a wider renovation, our home renovation cost guide shows where subfloor work usually sits.

Standards and Approvals

Like-for-like replacement of damaged subfloor timber is generally treated as a repair. Structural changes, such as removing piers or changing spans, can need an engineer’s design and sometimes approval. Residential timber framing in Australia is designed to AS 1684, and we size replacement timber to suit the span and load.

If the subfloor work is part of a renovation or extension, check what approval the whole project needs through the NSW Planning Portal or our guide to DA, CDC and exempt development.

Our Process

1. Inspection. We get under the house, check bearers, joists, supports, ventilation and moisture, and photograph what we find.
2. Clear quote. A subfloor repairs Sydney quote priced on what we found, with each repair itemised and the cause explained.
3. Repair. Propping, removal and replacement in the right order, with the floor supported throughout.
4. Cause fixed. Ventilation, clearance or drainage improvements so the damage does not come back.
5. Final check. Floor checked for level and movement, and before-and-after photos shared with you.

Subfloor Repairs Sydney: Areas We Service

We are based in Peakhurst and do subfloor repair work across the south of Sydney and beyond. The housing in each area brings its own subfloor problems.

Peakhurst and the Georges River area

Peakhurst, Riverwood, Lugarno, Mortdale, Penshurst, Oatley, Beverly Hills, Kingsgrove, Roselands and Padstow have a lot of post-war brick and fibro homes with timber floors over a subfloor space. Marginal ground clearance is common, so springy floors from decayed bearers and joists are one of our most frequent repairs here. See our carpentry services in Peakhurst.

St George

Hurstville, Kogarah, Carlton, Allawah, Blakehurst, South Hurstville, Ramsgate and Sans Souci. Older homes being renovated often reveal subfloor damage once the floors come up. See carpenter St George.

Inner West

Drummoyne, Rozelle, Balmain, Five Dock and surrounds. Terraces and federation homes with low, poorly ventilated subfloors and original timbers that have been patched over decades. See carpenter Rozelle and old home renovations.

Sutherland Shire

Menai, Sylvania, Caringbah, Miranda, Cronulla, Gymea, Engadine, Como and surrounds. Sloping blocks mean deep subfloors at one end and almost none at the other, and damp sites where stormwater runs under the house. See carpenter Sutherland Shire.

Bayside, Bankstown and greater Sydney

Rockdale, Brighton-Le-Sands, Bankstown, Revesby, Panania and wider Sydney, subject to access and scheduling. See our service areas page.

Why Choose Probuilding & Carpentry

• Licensed NSW carpenter, licence 458148C
• Owner-led work by Hamzah Elfoul, with more than eight years of hands-on experience
• Structural timber work, not cosmetic patching
• We fix the cause, not just the timber
• Before-and-after photos of the work under your floor
• Subfloor repairs Sydney homeowners, builders and strata managers use

Subfloor Repair Guides

• Subfloor repair cost Sydney: 2026 price guide: published price ranges for bearers, joists and stumps, and what drives the cost.
• Signs of damaged bearers and joists: the warning signs to look for inside and under the house.

Frequently Asked Questions

How much do subfloor repairs cost in Sydney?

Subfloor repairs Sydney costs depend on access under the house, how far the damage has spread, whether supports need replacing and whether the floor above has to come up. A few sistered joists and a full bearer replacement are very different jobs. We inspect first and price on what we find.

Can you replace floor joists without lifting the floor?

Often, yes. Most joists can be sistered or replaced from underneath if there is enough crawl space. Where access is too tight, or the flooring is also damaged, some sections may need to be lifted.

What are the signs of damaged bearers and joists?

Bouncy or sloping floors, gaps under skirting boards, doors that stick, new cracks in plaster, a musty smell under the house, and mud tubes from termites.

Do you fix the cause of the damage?

Yes. We point out what caused it, such as poor ventilation, low clearance, a leak or drainage, and include the fix in the quote so the new timber lasts.

What if there are termites?

Active termites need to be treated by a licensed pest controller first. Once the activity is dealt with, we replace the damaged timber.

Can a sagging floor be re-levelled?

Usually, yes. Once the failed supports and timbers are replaced, the floor can be packed and brought back towards level. Very old movement in walls and finishes may not fully close up.

How long does a subfloor repair take?

Small joist repairs can be done in a day or two. A bearer replacement or a larger area takes longer, depending on access and what we find. We give a time range with the quote.

Do you work for strata and builders?

Yes. We do subfloor repairs for homeowners, for builders as part of renovations, and for strata managers. See our strata repairs page.

Request a Quote

If your floor has started to bounce, slope or move, the next step is someone getting under the house to see why. Call Hamzah on 0449 576 839 or visit our contact page to book a subfloor repairs Sydney inspection and quote.

Related work: structural carpentry Sydney, timber framing Sydney, decking builder Sydney, bathroom renovation carpentry and demolition and removal.

Useful resources: verify a contractor licence through NSW Fair Trading. For timber framing guidance, see WoodSolutions.